//
// AssemblyReader.cs
//
// Author:
//   Jb Evain (jbevain@gmail.com)
//
// Copyright (c) 2008 - 2011 Jb Evain
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

using Mono.Collections.Generic;
using Mono.Cecil.Cil;
using Mono.Cecil.Metadata;
using Mono.Cecil.PE;

using RVA = System.UInt32;

namespace Mono.Cecil
{

    abstract class ModuleReader
    {

        readonly protected Image image;
        readonly protected ModuleDefinition module;

        protected ModuleReader(Image image, ReadingMode mode)
        {
            this.image = image;
            this.module = new ModuleDefinition(image);
            this.module.ReadingMode = mode;
        }

        protected abstract void ReadModule();

        protected void ReadModuleManifest(MetadataReader reader)
        {
            reader.Populate(module);

            ReadAssembly(reader);
        }

        void ReadAssembly(MetadataReader reader)
        {
            var name = reader.ReadAssemblyNameDefinition();
            if (name == null)
            {
                module.kind = ModuleKind.NetModule;
                return;
            }

            var assembly = new AssemblyDefinition();
            assembly.Name = name;

            module.assembly = assembly;
            assembly.main_module = module;
        }

        public static ModuleDefinition CreateModuleFrom(Image image, ReaderParameters parameters)
        {
            var module = ReadModule(image, parameters);

            ReadSymbols(module, parameters);

            if (parameters.AssemblyResolver != null)
                module.assembly_resolver = parameters.AssemblyResolver;

            if (parameters.MetadataResolver != null)
                module.metadata_resolver = parameters.MetadataResolver;

            return module;
        }

        static void ReadSymbols(ModuleDefinition module, ReaderParameters parameters)
        {
            var symbol_reader_provider = parameters.SymbolReaderProvider;

            if (symbol_reader_provider == null && parameters.ReadSymbols)
                symbol_reader_provider = SymbolProvider.GetPlatformReaderProvider();

            if (symbol_reader_provider != null)
            {
                module.SymbolReaderProvider = symbol_reader_provider;

                var reader = parameters.SymbolStream != null
                    ? symbol_reader_provider.GetSymbolReader(module, parameters.SymbolStream)
                    : symbol_reader_provider.GetSymbolReader(module, module.FullyQualifiedName);

                module.ReadSymbols(reader);
            }
        }

        static ModuleDefinition ReadModule(Image image, ReaderParameters parameters)
        {
            var reader = CreateModuleReader(image, parameters.ReadingMode);
            reader.ReadModule();
            return reader.module;
        }

        static ModuleReader CreateModuleReader(Image image, ReadingMode mode)
        {
            switch (mode)
            {
                case ReadingMode.Immediate:
                    return new ImmediateModuleReader(image);
                case ReadingMode.Deferred:
                    return new DeferredModuleReader(image);
                default:
                    throw new ArgumentException();
            }
        }
    }

    sealed class ImmediateModuleReader : ModuleReader
    {

        public ImmediateModuleReader(Image image)
            : base(image, ReadingMode.Immediate)
        {
        }

        protected override void ReadModule()
        {
            this.module.Read(this.module, (module, reader) =>
            {
                ReadModuleManifest(reader);
                ReadModule(module);
                return module;
            });
        }

        public static void ReadModule(ModuleDefinition module)
        {
            if (module.HasAssemblyReferences)
                Read(module.AssemblyReferences);
            if (module.HasResources)
                Read(module.Resources);
            if (module.HasModuleReferences)
                Read(module.ModuleReferences);
            if (module.HasTypes)
                ReadTypes(module.Types);
            if (module.HasExportedTypes)
                Read(module.ExportedTypes);
            if (module.HasCustomAttributes)
                Read(module.CustomAttributes);

            var assembly = module.Assembly;
            if (assembly == null)
                return;

            if (assembly.HasCustomAttributes)
                Read(assembly.CustomAttributes);
            if (assembly.HasSecurityDeclarations)
                Read(assembly.SecurityDeclarations);
        }

        static void ReadTypes(Collection<TypeDefinition> types)
        {
            for (int i = 0; i < types.Count; i++)
                ReadType(types[i]);
        }

        static void ReadType(TypeDefinition type)
        {
            ReadGenericParameters(type);

            if (type.HasInterfaces)
                Read(type.Interfaces);

            if (type.HasNestedTypes)
                ReadTypes(type.NestedTypes);

            if (type.HasLayoutInfo)
                Read(type.ClassSize);

            if (type.HasFields)
                ReadFields(type);

            if (type.HasMethods)
                ReadMethods(type);

            if (type.HasProperties)
                ReadProperties(type);

            if (type.HasEvents)
                ReadEvents(type);

            ReadSecurityDeclarations(type);
            ReadCustomAttributes(type);
        }

        static void ReadGenericParameters(IGenericParameterProvider provider)
        {
            if (!provider.HasGenericParameters)
                return;

            var parameters = provider.GenericParameters;

            for (int i = 0; i < parameters.Count; i++)
            {
                var parameter = parameters[i];

                if (parameter.HasConstraints)
                    Read(parameter.Constraints);

                if (parameter.HasCustomAttributes)
                    Read(parameter.CustomAttributes);
            }
        }

        static void ReadSecurityDeclarations(ISecurityDeclarationProvider provider)
        {
            if (provider.HasSecurityDeclarations)
                Read(provider.SecurityDeclarations);
        }

        static void ReadCustomAttributes(ICustomAttributeProvider provider)
        {
            if (provider.HasCustomAttributes)
                Read(provider.CustomAttributes);
        }

        static void ReadFields(TypeDefinition type)
        {
            var fields = type.Fields;

            for (int i = 0; i < fields.Count; i++)
            {
                var field = fields[i];

                if (field.HasConstant)
                    Read(field.Constant);

                if (field.HasLayoutInfo)
                    Read(field.Offset);

                if (field.RVA > 0)
                    Read(field.InitialValue);

                if (field.HasMarshalInfo)
                    Read(field.MarshalInfo);

                ReadCustomAttributes(field);
            }
        }

        static void ReadMethods(TypeDefinition type)
        {
            var methods = type.Methods;

            for (int i = 0; i < methods.Count; i++)
            {
                var method = methods[i];

                ReadGenericParameters(method);

                if (method.HasParameters)
                    ReadParameters(method);

                if (method.HasOverrides)
                    Read(method.Overrides);

                if (method.IsPInvokeImpl)
                    Read(method.PInvokeInfo);

                ReadSecurityDeclarations(method);
                ReadCustomAttributes(method);

                var return_type = method.MethodReturnType;
                if (return_type.HasConstant)
                    Read(return_type.Constant);

                if (return_type.HasMarshalInfo)
                    Read(return_type.MarshalInfo);

                ReadCustomAttributes(return_type);
            }
        }

        static void ReadParameters(MethodDefinition method)
        {
            var parameters = method.Parameters;

            for (int i = 0; i < parameters.Count; i++)
            {
                var parameter = parameters[i];

                if (parameter.HasConstant)
                    Read(parameter.Constant);

                if (parameter.HasMarshalInfo)
                    Read(parameter.MarshalInfo);

                ReadCustomAttributes(parameter);
            }
        }

        static void ReadProperties(TypeDefinition type)
        {
            var properties = type.Properties;

            for (int i = 0; i < properties.Count; i++)
            {
                var property = properties[i];

                Read(property.GetMethod);

                if (property.HasConstant)
                    Read(property.Constant);

                ReadCustomAttributes(property);
            }
        }

        static void ReadEvents(TypeDefinition type)
        {
            var events = type.Events;

            for (int i = 0; i < events.Count; i++)
            {
                var @event = events[i];

                Read(@event.AddMethod);

                ReadCustomAttributes(@event);
            }
        }

        static void Read(object collection)
        {
        }
    }

    sealed class DeferredModuleReader : ModuleReader
    {

        public DeferredModuleReader(Image image)
            : base(image, ReadingMode.Deferred)
        {
        }

        protected override void ReadModule()
        {
            this.module.Read(this.module, (module, reader) =>
            {
                ReadModuleManifest(reader);
                return module;
            });
        }
    }

    sealed class MetadataReader : ByteBuffer
    {

        readonly internal Image image;
        readonly internal ModuleDefinition module;
        readonly internal MetadataSystem metadata;

        internal IGenericContext context;
        internal CodeReader code;

        uint Position
        {
            get { return (uint)base.position; }
            set { base.position = (int)value; }
        }

        public MetadataReader(ModuleDefinition module)
            : base(module.Image.MetadataSection.Data)
        {
            this.image = module.Image;
            this.module = module;
            this.metadata = module.MetadataSystem;
            this.code = new CodeReader(image.MetadataSection, this);
        }

        int GetCodedIndexSize(CodedIndex index)
        {
            return image.GetCodedIndexSize(index);
        }

        uint ReadByIndexSize(int size)
        {
            if (size == 4)
                return ReadUInt32();
            else
                return ReadUInt16();
        }

        byte[] ReadBlob()
        {
            var blob_heap = image.BlobHeap;
            if (blob_heap == null)
            {
                position += 2;
                return Empty<byte>.Array;
            }

            return blob_heap.Read(ReadBlobIndex());
        }

        byte[] ReadBlob(uint signature)
        {
            var blob_heap = image.BlobHeap;
            if (blob_heap == null)
                return Empty<byte>.Array;

            return blob_heap.Read(signature);
        }

        uint ReadBlobIndex()
        {
            var blob_heap = image.BlobHeap;
            return ReadByIndexSize(blob_heap != null ? blob_heap.IndexSize : 2);
        }

        string ReadString()
        {
            return image.StringHeap.Read(ReadByIndexSize(image.StringHeap.IndexSize));
        }

        uint ReadStringIndex()
        {
            return ReadByIndexSize(image.StringHeap.IndexSize);
        }

        uint ReadTableIndex(Table table)
        {
            return ReadByIndexSize(image.GetTableIndexSize(table));
        }

        MetadataToken ReadMetadataToken(CodedIndex index)
        {
            return Mixin.GetMetadataToken(index, ReadByIndexSize(GetCodedIndexSize(index)));
        }

        int MoveTo(Table table)
        {
            var info = image.TableHeap[table];
            if (info.Length != 0)
                Position = info.Offset;

            return (int)info.Length;
        }

        bool MoveTo(Table table, uint row)
        {
            var info = image.TableHeap[table];
            var length = info.Length;
            if (length == 0 || row > length)
                return false;

            Position = info.Offset + (info.RowSize * (row - 1));
            return true;
        }

        public AssemblyNameDefinition ReadAssemblyNameDefinition()
        {
            if (MoveTo(Table.Assembly) == 0)
                return null;

            var name = new AssemblyNameDefinition();

            name.HashAlgorithm = (AssemblyHashAlgorithm)ReadUInt32();

            PopulateVersionAndFlags(name);

            name.PublicKey = ReadBlob();

            PopulateNameAndCulture(name);

            return name;
        }

        public ModuleDefinition Populate(ModuleDefinition module)
        {
            if (MoveTo(Table.Module) == 0)
                return module;

            Advance(2); // Generation

            module.Name = ReadString();
            module.Mvid = image.GuidHeap.Read(ReadByIndexSize(image.GuidHeap.IndexSize));

            return module;
        }

        void InitializeAssemblyReferences()
        {
            if (metadata.AssemblyReferences != null)
                return;

            int length = MoveTo(Table.AssemblyRef);
            var references = metadata.AssemblyReferences = new AssemblyNameReference[length];

            for (uint i = 0; i < length; i++)
            {
                var reference = new AssemblyNameReference();
                reference.token = new MetadataToken(TokenType.AssemblyRef, i + 1);

                PopulateVersionAndFlags(reference);

                var key_or_token = ReadBlob();

                if (reference.HasPublicKey)
                    reference.PublicKey = key_or_token;
                else
                    reference.PublicKeyToken = key_or_token;

                PopulateNameAndCulture(reference);

                reference.Hash = ReadBlob();

                references[i] = reference;
            }
        }

        public Collection<AssemblyNameReference> ReadAssemblyReferences()
        {
            InitializeAssemblyReferences();

            return new Collection<AssemblyNameReference>(metadata.AssemblyReferences);
        }

        public MethodDefinition ReadEntryPoint()
        {
            if (module.Image.EntryPointToken == 0)
                return null;

            var token = new MetadataToken(module.Image.EntryPointToken);
            return GetMethodDefinition(token.RID);
        }

        public Collection<ModuleDefinition> ReadModules()
        {
            var modules = new Collection<ModuleDefinition>(1);
            modules.Add(this.module);

            int length = MoveTo(Table.File);
            for (uint i = 1; i <= length; i++)
            {
                var attributes = (FileAttributes)ReadUInt32();
                var name = ReadString();
                ReadBlobIndex();

                if (attributes != FileAttributes.ContainsMetaData)
                    continue;

                var parameters = new ReaderParameters
                {
                    ReadingMode = module.ReadingMode,
                    SymbolReaderProvider = module.SymbolReaderProvider,
                };

                modules.Add(ModuleDefinition.ReadModule(
                    GetModuleFileName(name), parameters));
            }

            return modules;
        }

        string GetModuleFileName(string name)
        {
            if (module.FullyQualifiedName == null)
                throw new NotSupportedException();

            var path = Path.GetDirectoryName(module.FullyQualifiedName);
            return Path.Combine(path, name);
        }

        void InitializeModuleReferences()
        {
            if (metadata.ModuleReferences != null)
                return;

            int length = MoveTo(Table.ModuleRef);
            var references = metadata.ModuleReferences = new ModuleReference[length];

            for (uint i = 0; i < length; i++)
            {
                var reference = new ModuleReference(ReadString());
                reference.token = new MetadataToken(TokenType.ModuleRef, i + 1);

                references[i] = reference;
            }
        }

        public Collection<ModuleReference> ReadModuleReferences()
        {
            InitializeModuleReferences();

            return new Collection<ModuleReference>(metadata.ModuleReferences);
        }

        public bool HasFileResource()
        {
            int length = MoveTo(Table.File);
            if (length == 0)
                return false;

            for (uint i = 1; i <= length; i++)
                if (ReadFileRecord(i).Col1 == FileAttributes.ContainsNoMetaData)
                    return true;

            return false;
        }

        public Collection<Resource> ReadResources()
        {
            int length = MoveTo(Table.ManifestResource);
            var resources = new Collection<Resource>(length);

            for (int i = 1; i <= length; i++)
            {
                var offset = ReadUInt32();
                var flags = (ManifestResourceAttributes)ReadUInt32();
                var name = ReadString();
                var implementation = ReadMetadataToken(CodedIndex.Implementation);

                Resource resource;

                if (implementation.RID == 0)
                {
                    resource = new EmbeddedResource(name, flags, offset, this);
                }
                else if (implementation.TokenType == TokenType.AssemblyRef)
                {
                    resource = new AssemblyLinkedResource(name, flags)
                    {
                        Assembly = (AssemblyNameReference)GetTypeReferenceScope(implementation),
                    };
                }
                else if (implementation.TokenType == TokenType.File)
                {
                    var file_record = ReadFileRecord(implementation.RID);

                    resource = new LinkedResource(name, flags)
                    {
                        File = file_record.Col2,
                        hash = ReadBlob(file_record.Col3)
                    };
                }
                else
                    throw new NotSupportedException();

                resources.Add(resource);
            }

            return resources;
        }

        Row<FileAttributes, string, uint> ReadFileRecord(uint rid)
        {
            var position = this.position;

            if (!MoveTo(Table.File, rid))
                throw new ArgumentException();

            var record = new Row<FileAttributes, string, uint>(
                (FileAttributes)ReadUInt32(),
                ReadString(),
                ReadBlobIndex());

            this.position = position;

            return record;
        }

        public MemoryStream GetManagedResourceStream(uint offset)
        {
            var rva = image.Resources.VirtualAddress;
            var section = image.GetSectionAtVirtualAddress(rva);
            var position = (rva - section.VirtualAddress) + offset;
            var buffer = section.Data;

            var length = buffer[position]
                | (buffer[position + 1] << 8)
                | (buffer[position + 2] << 16)
                | (buffer[position + 3] << 24);

            return new MemoryStream(buffer, (int)position + 4, length);
        }

        void PopulateVersionAndFlags(AssemblyNameReference name)
        {
            name.Version = new Version(
                ReadUInt16(),
                ReadUInt16(),
                ReadUInt16(),
                ReadUInt16());

            name.Attributes = (AssemblyAttributes)ReadUInt32();
        }

        void PopulateNameAndCulture(AssemblyNameReference name)
        {
            name.Name = ReadString();
            name.Culture = ReadString();
        }

        public TypeDefinitionCollection ReadTypes()
        {
            InitializeTypeDefinitions();
            var mtypes = metadata.Types;
            var type_count = mtypes.Length - metadata.NestedTypes.Count;
            var types = new TypeDefinitionCollection(module, type_count);

            for (int i = 0; i < mtypes.Length; i++)
            {
                var type = mtypes[i];
                if (IsNested(type.Attributes))
                    continue;

                types.Add(type);
            }

            if (image.HasTable(Table.MethodPtr) || image.HasTable(Table.FieldPtr))
                CompleteTypes();

            return types;
        }

        void CompleteTypes()
        {
            var types = metadata.Types;

            for (int i = 0; i < types.Length; i++)
            {
                var type = types[i];

                InitializeCollection(type.Fields);
                InitializeCollection(type.Methods);
            }
        }

        void InitializeTypeDefinitions()
        {
            if (metadata.Types != null)
                return;

            InitializeNestedTypes();
            InitializeFields();
            InitializeMethods();

            int length = MoveTo(Table.TypeDef);
            var types = metadata.Types = new TypeDefinition[length];

            for (uint i = 0; i < length; i++)
            {
                if (types[i] != null)
                    continue;

                types[i] = ReadType(i + 1);
            }
        }

        static bool IsNested(TypeAttributes attributes)
        {
            switch (attributes & TypeAttributes.VisibilityMask)
            {
                case TypeAttributes.NestedAssembly:
                case TypeAttributes.NestedFamANDAssem:
                case TypeAttributes.NestedFamily:
                case TypeAttributes.NestedFamORAssem:
                case TypeAttributes.NestedPrivate:
                case TypeAttributes.NestedPublic:
                    return true;
                default:
                    return false;
            }
        }

        public bool HasNestedTypes(TypeDefinition type)
        {
            uint[] mapping;
            InitializeNestedTypes();

            if (!metadata.TryGetNestedTypeMapping(type, out mapping))
                return false;

            return mapping.Length > 0;
        }

        public Collection<TypeDefinition> ReadNestedTypes(TypeDefinition type)
        {
            InitializeNestedTypes();
            uint[] mapping;
            if (!metadata.TryGetNestedTypeMapping(type, out mapping))
                return new MemberDefinitionCollection<TypeDefinition>(type);

            var nested_types = new MemberDefinitionCollection<TypeDefinition>(type, mapping.Length);

            for (int i = 0; i < mapping.Length; i++)
            {
                var nested_type = GetTypeDefinition(mapping[i]);

                if (nested_type != null)
                    nested_types.Add(nested_type);
            }

            metadata.RemoveNestedTypeMapping(type);

            return nested_types;
        }

        void InitializeNestedTypes()
        {
            if (metadata.NestedTypes != null)
                return;

            var length = MoveTo(Table.NestedClass);

            metadata.NestedTypes = new Dictionary<uint, uint[]>(length);
            metadata.ReverseNestedTypes = new Dictionary<uint, uint>(length);

            if (length == 0)
                return;

            for (int i = 1; i <= length; i++)
            {
                var nested = ReadTableIndex(Table.TypeDef);
                var declaring = ReadTableIndex(Table.TypeDef);

                AddNestedMapping(declaring, nested);
            }
        }

        void AddNestedMapping(uint declaring, uint nested)
        {
            metadata.SetNestedTypeMapping(declaring, AddMapping(metadata.NestedTypes, declaring, nested));
            metadata.SetReverseNestedTypeMapping(nested, declaring);
        }

        static TValue[] AddMapping<TKey, TValue>(Dictionary<TKey, TValue[]> cache, TKey key, TValue value)
        {
            TValue[] mapped;
            if (!cache.TryGetValue(key, out mapped))
            {
                mapped = new[] { value };
                return mapped;
            }

            var new_mapped = new TValue[mapped.Length + 1];
            Array.Copy(mapped, new_mapped, mapped.Length);
            new_mapped[mapped.Length] = value;
            return new_mapped;
        }

        TypeDefinition ReadType(uint rid)
        {
            if (!MoveTo(Table.TypeDef, rid))
                return null;

            var attributes = (TypeAttributes)ReadUInt32();
            var name = ReadString();
            var @namespace = ReadString();
            var type = new TypeDefinition(@namespace, name, attributes);
            type.token = new MetadataToken(TokenType.TypeDef, rid);
            type.scope = module;
            type.module = module;

            metadata.AddTypeDefinition(type);

            this.context = type;

            type.BaseType = GetTypeDefOrRef(ReadMetadataToken(CodedIndex.TypeDefOrRef));

            type.fields_range = ReadFieldsRange(rid);
            type.methods_range = ReadMethodsRange(rid);

            if (IsNested(attributes))
                type.DeclaringType = GetNestedTypeDeclaringType(type);

            return type;
        }

        TypeDefinition GetNestedTypeDeclaringType(TypeDefinition type)
        {
            uint declaring_rid;
            if (!metadata.TryGetReverseNestedTypeMapping(type, out declaring_rid))
                return null;

            metadata.RemoveReverseNestedTypeMapping(type);
            return GetTypeDefinition(declaring_rid);
        }

        Range ReadFieldsRange(uint type_index)
        {
            return ReadListRange(type_index, Table.TypeDef, Table.Field);
        }

        Range ReadMethodsRange(uint type_index)
        {
            return ReadListRange(type_index, Table.TypeDef, Table.Method);
        }

        Range ReadListRange(uint current_index, Table current, Table target)
        {
            var list = new Range();

            list.Start = ReadTableIndex(target);

            uint next_index;
            var current_table = image.TableHeap[current];

            if (current_index == current_table.Length)
                next_index = image.TableHeap[target].Length + 1;
            else
            {
                var position = Position;
                Position += (uint)(current_table.RowSize - image.GetTableIndexSize(target));
                next_index = ReadTableIndex(target);
                Position = position;
            }

            list.Length = next_index - list.Start;

            return list;
        }

        public Row<short, int> ReadTypeLayout(TypeDefinition type)
        {
            InitializeTypeLayouts();
            Row<ushort, uint> class_layout;
            var rid = type.token.RID;
            if (!metadata.ClassLayouts.TryGetValue(rid, out class_layout))
                return new Row<short, int>(Mixin.NoDataMarker, Mixin.NoDataMarker);

            type.PackingSize = (short)class_layout.Col1;
            type.ClassSize = (int)class_layout.Col2;

            metadata.ClassLayouts.Remove(rid);

            return new Row<short, int>((short)class_layout.Col1, (int)class_layout.Col2);
        }

        void InitializeTypeLayouts()
        {
            if (metadata.ClassLayouts != null)
                return;

            int length = MoveTo(Table.ClassLayout);

            var class_layouts = metadata.ClassLayouts = new Dictionary<uint, Row<ushort, uint>>(length);

            for (uint i = 0; i < length; i++)
            {
                var packing_size = ReadUInt16();
                var class_size = ReadUInt32();

                var parent = ReadTableIndex(Table.TypeDef);

                class_layouts.Add(parent, new Row<ushort, uint>(packing_size, class_size));
            }
        }

        public TypeReference GetTypeDefOrRef(MetadataToken token)
        {
            return (TypeReference)LookupToken(token);
        }

        public TypeDefinition GetTypeDefinition(uint rid)
        {
            InitializeTypeDefinitions();

            var type = metadata.GetTypeDefinition(rid);
            if (type != null)
                return type;

            return ReadTypeDefinition(rid);
        }

        TypeDefinition ReadTypeDefinition(uint rid)
        {
            if (!MoveTo(Table.TypeDef, rid))
                return null;

            return ReadType(rid);
        }

        void InitializeTypeReferences()
        {
            if (metadata.TypeReferences != null)
                return;

            metadata.TypeReferences = new TypeReference[image.GetTableLength(Table.TypeRef)];
        }

        public TypeReference GetTypeReference(string scope, string full_name)
        {
            InitializeTypeReferences();

            var length = metadata.TypeReferences.Length;

            for (uint i = 1; i <= length; i++)
            {
                var type = GetTypeReference(i);

                if (type.FullName != full_name)
                    continue;

                if (string.IsNullOrEmpty(scope))
                    return type;

                if (type.Scope.Name == scope)
                    return type;
            }

            return null;
        }

        TypeReference GetTypeReference(uint rid)
        {
            InitializeTypeReferences();

            var type = metadata.GetTypeReference(rid);
            if (type != null)
                return type;

            return ReadTypeReference(rid);
        }

        TypeReference ReadTypeReference(uint rid)
        {
            if (!MoveTo(Table.TypeRef, rid))
                return null;

            TypeReference declaring_type = null;
            IMetadataScope scope;

            var scope_token = ReadMetadataToken(CodedIndex.ResolutionScope);

            var name = ReadString();
            var @namespace = ReadString();

            var type = new TypeReference(
                @namespace,
                name,
                module,
                null);

            type.token = new MetadataToken(TokenType.TypeRef, rid);

            metadata.AddTypeReference(type);

            if (scope_token.TokenType == TokenType.TypeRef)
            {
                declaring_type = GetTypeDefOrRef(scope_token);

                scope = declaring_type != null
                    ? declaring_type.Scope
                    : module;
            }
            else
                scope = GetTypeReferenceScope(scope_token);

            type.scope = scope;
            type.DeclaringType = declaring_type;

            MetadataSystem.TryProcessPrimitiveTypeReference(type);

            return type;
        }

        IMetadataScope GetTypeReferenceScope(MetadataToken scope)
        {
            switch (scope.TokenType)
            {
                case TokenType.AssemblyRef:
                    InitializeAssemblyReferences();
                    return metadata.AssemblyReferences[(int)scope.RID - 1];
                case TokenType.ModuleRef:
                    InitializeModuleReferences();
                    return metadata.ModuleReferences[(int)scope.RID - 1];
                case TokenType.Module:
                    return module;
                default:
                    throw new NotSupportedException();
            }
        }

        public IEnumerable<TypeReference> GetTypeReferences()
        {
            InitializeTypeReferences();

            var length = image.GetTableLength(Table.TypeRef);

            var type_references = new TypeReference[length];

            for (uint i = 1; i <= length; i++)
                type_references[i - 1] = GetTypeReference(i);

            return type_references;
        }

        TypeReference GetTypeSpecification(uint rid)
        {
            if (!MoveTo(Table.TypeSpec, rid))
                return null;

            var reader = ReadSignature(ReadBlobIndex());
            var type = reader.ReadTypeSignature();
            if (type.token.RID == 0)
                type.token = new MetadataToken(TokenType.TypeSpec, rid);

            return type;
        }

        SignatureReader ReadSignature(uint signature)
        {
            return new SignatureReader(signature, this);
        }

        public bool HasInterfaces(TypeDefinition type)
        {
            InitializeInterfaces();
            MetadataToken[] mapping;

            return metadata.TryGetInterfaceMapping(type, out mapping);
        }

        public Collection<TypeReference> ReadInterfaces(TypeDefinition type)
        {
            InitializeInterfaces();
            MetadataToken[] mapping;

            if (!metadata.TryGetInterfaceMapping(type, out mapping))
                return new Collection<TypeReference>();

            var interfaces = new Collection<TypeReference>(mapping.Length);

            this.context = type;

            for (int i = 0; i < mapping.Length; i++)
                interfaces.Add(GetTypeDefOrRef(mapping[i]));

            metadata.RemoveInterfaceMapping(type);

            return interfaces;
        }

        void InitializeInterfaces()
        {
            if (metadata.Interfaces != null)
                return;

            int length = MoveTo(Table.InterfaceImpl);

            metadata.Interfaces = new Dictionary<uint, MetadataToken[]>(length);

            for (int i = 0; i < length; i++)
            {
                var type = ReadTableIndex(Table.TypeDef);
                var @interface = ReadMetadataToken(CodedIndex.TypeDefOrRef);

                AddInterfaceMapping(type, @interface);
            }
        }

        void AddInterfaceMapping(uint type, MetadataToken @interface)
        {
            metadata.SetInterfaceMapping(type, AddMapping(metadata.Interfaces, type, @interface));
        }

        public Collection<FieldDefinition> ReadFields(TypeDefinition type)
        {
            var fields_range = type.fields_range;
            if (fields_range.Length == 0)
                return new MemberDefinitionCollection<FieldDefinition>(type);

            var fields = new MemberDefinitionCollection<FieldDefinition>(type, (int)fields_range.Length);
            this.context = type;

            if (!MoveTo(Table.FieldPtr, fields_range.Start))
            {
                if (!MoveTo(Table.Field, fields_range.Start))
                    return fields;

                for (uint i = 0; i < fields_range.Length; i++)
                    ReadField(fields_range.Start + i, fields);
            }
            else
                ReadPointers(Table.FieldPtr, Table.Field, fields_range, fields, ReadField);

            return fields;
        }

        void ReadField(uint field_rid, Collection<FieldDefinition> fields)
        {
            var attributes = (FieldAttributes)ReadUInt16();
            var name = ReadString();
            var signature = ReadBlobIndex();

            var field = new FieldDefinition(name, attributes, ReadFieldType(signature));
            field.token = new MetadataToken(TokenType.Field, field_rid);
            metadata.AddFieldDefinition(field);

            if (IsDeleted(field))
                return;

            fields.Add(field);
        }

        void InitializeFields()
        {
            if (metadata.Fields != null)
                return;

            metadata.Fields = new FieldDefinition[image.GetTableLength(Table.Field)];
        }

        TypeReference ReadFieldType(uint signature)
        {
            var reader = ReadSignature(signature);

            const byte field_sig = 0x6;

            if (reader.ReadByte() != field_sig)
                throw new NotSupportedException();

            return reader.ReadTypeSignature();
        }

        public int ReadFieldRVA(FieldDefinition field)
        {
            InitializeFieldRVAs();
            var rid = field.token.RID;

            RVA rva;
            if (!metadata.FieldRVAs.TryGetValue(rid, out rva))
                return 0;

            var size = GetFieldTypeSize(field.FieldType);

            if (size == 0 || rva == 0)
                return 0;

            metadata.FieldRVAs.Remove(rid);

            field.InitialValue = GetFieldInitializeValue(size, rva);

            return (int)rva;
        }

        byte[] GetFieldInitializeValue(int size, RVA rva)
        {
            var section = image.GetSectionAtVirtualAddress(rva);
            if (section == null)
                return Empty<byte>.Array;

            var value = new byte[size];
            Buffer.BlockCopy(section.Data, (int)(rva - section.VirtualAddress), value, 0, size);
            return value;
        }

        static int GetFieldTypeSize(TypeReference type)
        {
            int size = 0;

            switch (type.etype)
            {
                case ElementType.Boolean:
                case ElementType.U1:
                case ElementType.I1:
                    size = 1;
                    break;
                case ElementType.U2:
                case ElementType.I2:
                case ElementType.Char:
                    size = 2;
                    break;
                case ElementType.U4:
                case ElementType.I4:
                case ElementType.R4:
                    size = 4;
                    break;
                case ElementType.U8:
                case ElementType.I8:
                case ElementType.R8:
                    size = 8;
                    break;
                case ElementType.Ptr:
                case ElementType.FnPtr:
                    size = IntPtr.Size;
                    break;
                case ElementType.CModOpt:
                case ElementType.CModReqD:
                    return GetFieldTypeSize(((IModifierType)type).ElementType);
                default:
                    var field_type = Mixin.CheckedResolve(type);
                    if (field_type.HasLayoutInfo)
                        size = field_type.ClassSize;

                    break;
            }

            return size;
        }

        void InitializeFieldRVAs()
        {
            if (metadata.FieldRVAs != null)
                return;

            int length = MoveTo(Table.FieldRVA);

            var field_rvas = metadata.FieldRVAs = new Dictionary<uint, uint>(length);

            for (int i = 0; i < length; i++)
            {
                var rva = ReadUInt32();
                var field = ReadTableIndex(Table.Field);

                field_rvas.Add(field, rva);
            }
        }

        public int ReadFieldLayout(FieldDefinition field)
        {
            InitializeFieldLayouts();
            var rid = field.token.RID;
            uint offset;
            if (!metadata.FieldLayouts.TryGetValue(rid, out offset))
                return Mixin.NoDataMarker;

            metadata.FieldLayouts.Remove(rid);

            return (int)offset;
        }

        void InitializeFieldLayouts()
        {
            if (metadata.FieldLayouts != null)
                return;

            int length = MoveTo(Table.FieldLayout);

            var field_layouts = metadata.FieldLayouts = new Dictionary<uint, uint>(length);

            for (int i = 0; i < length; i++)
            {
                var offset = ReadUInt32();
                var field = ReadTableIndex(Table.Field);

                field_layouts.Add(field, offset);
            }
        }

        public bool HasEvents(TypeDefinition type)
        {
            InitializeEvents();

            Range range;
            if (!metadata.TryGetEventsRange(type, out range))
                return false;

            return range.Length > 0;
        }

        public Collection<EventDefinition> ReadEvents(TypeDefinition type)
        {
            InitializeEvents();
            Range range;

            if (!metadata.TryGetEventsRange(type, out range))
                return new MemberDefinitionCollection<EventDefinition>(type);

            var events = new MemberDefinitionCollection<EventDefinition>(type, (int)range.Length);

            metadata.RemoveEventsRange(type);

            if (range.Length == 0)
                return events;

            this.context = type;

            if (!MoveTo(Table.EventPtr, range.Start))
            {
                if (!MoveTo(Table.Event, range.Start))
                    return events;

                for (uint i = 0; i < range.Length; i++)
                    ReadEvent(range.Start + i, events);
            }
            else
                ReadPointers(Table.EventPtr, Table.Event, range, events, ReadEvent);

            return events;
        }

        void ReadEvent(uint event_rid, Collection<EventDefinition> events)
        {
            var attributes = (EventAttributes)ReadUInt16();
            var name = ReadString();
            var event_type = GetTypeDefOrRef(ReadMetadataToken(CodedIndex.TypeDefOrRef));

            var @event = new EventDefinition(name, attributes, event_type);
            @event.token = new MetadataToken(TokenType.Event, event_rid);

            if (IsDeleted(@event))
                return;

            events.Add(@event);
        }

        void InitializeEvents()
        {
            if (metadata.Events != null)
                return;

            int length = MoveTo(Table.EventMap);

            metadata.Events = new Dictionary<uint, Range>(length);

            for (uint i = 1; i <= length; i++)
            {
                var type_rid = ReadTableIndex(Table.TypeDef);
                Range events_range = ReadEventsRange(i);
                metadata.AddEventsRange(type_rid, events_range);
            }
        }

        Range ReadEventsRange(uint rid)
        {
            return ReadListRange(rid, Table.EventMap, Table.Event);
        }

        public bool HasProperties(TypeDefinition type)
        {
            InitializeProperties();

            Range range;
            if (!metadata.TryGetPropertiesRange(type, out range))
                return false;

            return range.Length > 0;
        }

        public Collection<PropertyDefinition> ReadProperties(TypeDefinition type)
        {
            InitializeProperties();

            Range range;

            if (!metadata.TryGetPropertiesRange(type, out range))
                return new MemberDefinitionCollection<PropertyDefinition>(type);

            metadata.RemovePropertiesRange(type);

            var properties = new MemberDefinitionCollection<PropertyDefinition>(type, (int)range.Length);

            if (range.Length == 0)
                return properties;

            this.context = type;

            if (!MoveTo(Table.PropertyPtr, range.Start))
            {
                if (!MoveTo(Table.Property, range.Start))
                    return properties;
                for (uint i = 0; i < range.Length; i++)
                    ReadProperty(range.Start + i, properties);
            }
            else
                ReadPointers(Table.PropertyPtr, Table.Property, range, properties, ReadProperty);

            return properties;
        }

        void ReadProperty(uint property_rid, Collection<PropertyDefinition> properties)
        {
            var attributes = (PropertyAttributes)ReadUInt16();
            var name = ReadString();
            var signature = ReadBlobIndex();

            var reader = ReadSignature(signature);
            const byte property_signature = 0x8;

            var calling_convention = reader.ReadByte();

            if ((calling_convention & property_signature) == 0)
                throw new NotSupportedException();

            var has_this = (calling_convention & 0x20) != 0;

            reader.ReadCompressedUInt32(); // count

            var property = new PropertyDefinition(name, attributes, reader.ReadTypeSignature());
            property.HasThis = has_this;
            property.token = new MetadataToken(TokenType.Property, property_rid);

            if (IsDeleted(property))
                return;

            properties.Add(property);
        }

        void InitializeProperties()
        {
            if (metadata.Properties != null)
                return;

            int length = MoveTo(Table.PropertyMap);

            metadata.Properties = new Dictionary<uint, Range>(length);

            for (uint i = 1; i <= length; i++)
            {
                var type_rid = ReadTableIndex(Table.TypeDef);
                var properties_range = ReadPropertiesRange(i);
                metadata.AddPropertiesRange(type_rid, properties_range);
            }
        }

        Range ReadPropertiesRange(uint rid)
        {
            return ReadListRange(rid, Table.PropertyMap, Table.Property);
        }

        MethodSemanticsAttributes ReadMethodSemantics(MethodDefinition method)
        {
            InitializeMethodSemantics();
            Row<MethodSemanticsAttributes, MetadataToken> row;
            if (!metadata.Semantics.TryGetValue(method.token.RID, out row))
                return MethodSemanticsAttributes.None;

            var type = method.DeclaringType;

            switch (row.Col1)
            {
                case MethodSemanticsAttributes.AddOn:
                    GetEvent(type, row.Col2).add_method = method;
                    break;
                case MethodSemanticsAttributes.Fire:
                    GetEvent(type, row.Col2).invoke_method = method;
                    break;
                case MethodSemanticsAttributes.RemoveOn:
                    GetEvent(type, row.Col2).remove_method = method;
                    break;
                case MethodSemanticsAttributes.Getter:
                    GetProperty(type, row.Col2).get_method = method;
                    break;
                case MethodSemanticsAttributes.Setter:
                    GetProperty(type, row.Col2).set_method = method;
                    break;
                case MethodSemanticsAttributes.Other:
                    switch (row.Col2.TokenType)
                    {
                        case TokenType.Event:
                            {
                                var @event = GetEvent(type, row.Col2);
                                if (@event.other_methods == null)
                                    @event.other_methods = new Collection<MethodDefinition>();

                                @event.other_methods.Add(method);
                                break;
                            }
                        case TokenType.Property:
                            {
                                var property = GetProperty(type, row.Col2);
                                if (property.other_methods == null)
                                    property.other_methods = new Collection<MethodDefinition>();

                                property.other_methods.Add(method);

                                break;
                            }
                        default:
                            throw new NotSupportedException();
                    }
                    break;
                default:
                    throw new NotSupportedException();
            }

            metadata.Semantics.Remove(method.token.RID);

            return row.Col1;
        }

        static EventDefinition GetEvent(TypeDefinition type, MetadataToken token)
        {
            if (token.TokenType != TokenType.Event)
                throw new ArgumentException();

            return GetMember(type.Events, token);
        }

        static PropertyDefinition GetProperty(TypeDefinition type, MetadataToken token)
        {
            if (token.TokenType != TokenType.Property)
                throw new ArgumentException();

            return GetMember(type.Properties, token);
        }

        static TMember GetMember<TMember>(Collection<TMember> members, MetadataToken token) where TMember : IMemberDefinition
        {
            for (int i = 0; i < members.Count; i++)
            {
                var member = members[i];
                if (member.MetadataToken == token)
                    return member;
            }

            throw new ArgumentException();
        }

        void InitializeMethodSemantics()
        {
            if (metadata.Semantics != null)
                return;

            int length = MoveTo(Table.MethodSemantics);

            var semantics = metadata.Semantics = new Dictionary<uint, Row<MethodSemanticsAttributes, MetadataToken>>(0);

            for (uint i = 0; i < length; i++)
            {
                var attributes = (MethodSemanticsAttributes)ReadUInt16();
                var method_rid = ReadTableIndex(Table.Method);
                var association = ReadMetadataToken(CodedIndex.HasSemantics);

                semantics[method_rid] = new Row<MethodSemanticsAttributes, MetadataToken>(attributes, association);
            }
        }

        public PropertyDefinition ReadMethods(PropertyDefinition property)
        {
            ReadAllSemantics(property.DeclaringType);
            return property;
        }

        public EventDefinition ReadMethods(EventDefinition @event)
        {
            ReadAllSemantics(@event.DeclaringType);
            return @event;
        }

        public MethodSemanticsAttributes ReadAllSemantics(MethodDefinition method)
        {
            ReadAllSemantics(method.DeclaringType);

            return method.SemanticsAttributes;
        }

        void ReadAllSemantics(TypeDefinition type)
        {
            var methods = type.Methods;
            for (int i = 0; i < methods.Count; i++)
            {
                var method = methods[i];
                if (method.sem_attrs_ready)
                    continue;

                method.sem_attrs = ReadMethodSemantics(method);
                method.sem_attrs_ready = true;
            }
        }

        Range ReadParametersRange(uint method_rid)
        {
            return ReadListRange(method_rid, Table.Method, Table.Param);
        }

        public Collection<MethodDefinition> ReadMethods(TypeDefinition type)
        {
            var methods_range = type.methods_range;
            if (methods_range.Length == 0)
                return new MemberDefinitionCollection<MethodDefinition>(type);

            var methods = new MemberDefinitionCollection<MethodDefinition>(type, (int)methods_range.Length);
            if (!MoveTo(Table.MethodPtr, methods_range.Start))
            {
                if (!MoveTo(Table.Method, methods_range.Start))
                    return methods;

                for (uint i = 0; i < methods_range.Length; i++)
                    ReadMethod(methods_range.Start + i, methods);
            }
            else
                ReadPointers(Table.MethodPtr, Table.Method, methods_range, methods, ReadMethod);

            return methods;
        }

        void ReadPointers<TMember>(Table ptr, Table table, Range range, Collection<TMember> members, Action<uint, Collection<TMember>> reader)
            where TMember : IMemberDefinition
        {
            for (uint i = 0; i < range.Length; i++)
            {
                MoveTo(ptr, range.Start + i);

                var rid = ReadTableIndex(table);
                MoveTo(table, rid);

                reader(rid, members);
            }
        }

        static bool IsDeleted(IMemberDefinition member)
        {
            return member.IsSpecialName && member.Name == "_Deleted";
        }

        void InitializeMethods()
        {
            if (metadata.Methods != null)
                return;

            metadata.Methods = new MethodDefinition[image.GetTableLength(Table.Method)];
        }

        void ReadMethod(uint method_rid, Collection<MethodDefinition> methods)
        {
            var method = new MethodDefinition();
            method.rva = ReadUInt32();
            method.ImplAttributes = (MethodImplAttributes)ReadUInt16();
            method.Attributes = (MethodAttributes)ReadUInt16();
            method.Name = ReadString();
            method.token = new MetadataToken(TokenType.Method, method_rid);

            if (IsDeleted(method))
                return;

            methods.Add(method); // attach method

            var signature = ReadBlobIndex();
            var param_range = ReadParametersRange(method_rid);

            this.context = method;

            ReadMethodSignature(signature, method);
            metadata.AddMethodDefinition(method);

            if (param_range.Length == 0)
                return;

            var position = base.position;
            ReadParameters(method, param_range);
            base.position = position;
        }

        void ReadParameters(MethodDefinition method, Range param_range)
        {
            if (!MoveTo(Table.ParamPtr, param_range.Start))
            {
                if (!MoveTo(Table.Param, param_range.Start))
                    return;

                for (uint i = 0; i < param_range.Length; i++)
                    ReadParameter(param_range.Start + i, method);
            }
            else
                ReadParameterPointers(method, param_range);
        }

        void ReadParameterPointers(MethodDefinition method, Range range)
        {
            for (uint i = 0; i < range.Length; i++)
            {
                MoveTo(Table.ParamPtr, range.Start + i);

                var rid = ReadTableIndex(Table.Param);

                MoveTo(Table.Param, rid);

                ReadParameter(rid, method);
            }
        }

        void ReadParameter(uint param_rid, MethodDefinition method)
        {
            var attributes = (ParameterAttributes)ReadUInt16();
            var sequence = ReadUInt16();
            var name = ReadString();

            var parameter = sequence == 0
                ? method.MethodReturnType.Parameter
                : method.Parameters[sequence - 1];

            parameter.token = new MetadataToken(TokenType.Param, param_rid);
            parameter.Name = name;
            parameter.Attributes = attributes;
        }

        void ReadMethodSignature(uint signature, IMethodSignature method)
        {
            var reader = ReadSignature(signature);
            reader.ReadMethodSignature(method);
        }

        public PInvokeInfo ReadPInvokeInfo(MethodDefinition method)
        {
            InitializePInvokes();
            Row<PInvokeAttributes, uint, uint> row;

            var rid = method.token.RID;

            if (!metadata.PInvokes.TryGetValue(rid, out row))
                return null;

            metadata.PInvokes.Remove(rid);

            return new PInvokeInfo(
                row.Col1,
                image.StringHeap.Read(row.Col2),
                module.ModuleReferences[(int)row.Col3 - 1]);
        }

        void InitializePInvokes()
        {
            if (metadata.PInvokes != null)
                return;

            int length = MoveTo(Table.ImplMap);

            var pinvokes = metadata.PInvokes = new Dictionary<uint, Row<PInvokeAttributes, uint, uint>>(length);

            for (int i = 1; i <= length; i++)
            {
                var attributes = (PInvokeAttributes)ReadUInt16();
                var method = ReadMetadataToken(CodedIndex.MemberForwarded);
                var name = ReadStringIndex();
                var scope = ReadTableIndex(Table.File);

                if (method.TokenType != TokenType.Method)
                    continue;

                pinvokes.Add(method.RID, new Row<PInvokeAttributes, uint, uint>(attributes, name, scope));
            }
        }

        public bool HasGenericParameters(IGenericParameterProvider provider)
        {
            InitializeGenericParameters();

            Range range;
            if (!metadata.TryGetGenericParameterRange(provider, out range))
                return false;

            return range.Length > 0;
        }

        public Collection<GenericParameter> ReadGenericParameters(IGenericParameterProvider provider)
        {
            InitializeGenericParameters();

            Range range;
            if (!metadata.TryGetGenericParameterRange(provider, out range)
                || !MoveTo(Table.GenericParam, range.Start))
                return new GenericParameterCollection(provider);

            metadata.RemoveGenericParameterRange(provider);

            var generic_parameters = new GenericParameterCollection(provider, (int)range.Length);

            for (uint i = 0; i < range.Length; i++)
            {
                ReadUInt16(); // index
                var flags = (GenericParameterAttributes)ReadUInt16();
                ReadMetadataToken(CodedIndex.TypeOrMethodDef);
                var name = ReadString();

                var parameter = new GenericParameter(name, provider);
                parameter.token = new MetadataToken(TokenType.GenericParam, range.Start + i);
                parameter.Attributes = flags;

                generic_parameters.Add(parameter);
            }

            return generic_parameters;
        }

        void InitializeGenericParameters()
        {
            if (metadata.GenericParameters != null)
                return;

            metadata.GenericParameters = InitializeRanges(
                Table.GenericParam, () =>
                {
                    Advance(4);
                    var next = ReadMetadataToken(CodedIndex.TypeOrMethodDef);
                    ReadStringIndex();
                    return next;
                });
        }

        Dictionary<MetadataToken, Range> InitializeRanges(Table table, Func<MetadataToken> get_next)
        {
            int length = MoveTo(table);
            var ranges = new Dictionary<MetadataToken, Range>(length);

            if (length == 0)
                return ranges;

            MetadataToken owner = MetadataToken.Zero;
            Range range = new Range(1, 0);

            for (uint i = 1; i <= length; i++)
            {
                var next = get_next();

                if (i == 1)
                {
                    owner = next;
                    range.Length++;
                }
                else if (next != owner)
                {
                    if (owner.RID != 0)
                        ranges.Add(owner, range);
                    range = new Range(i, 1);
                    owner = next;
                }
                else
                    range.Length++;
            }

            if (owner != MetadataToken.Zero && !ranges.ContainsKey(owner))
                ranges.Add(owner, range);

            return ranges;
        }

        public bool HasGenericConstraints(GenericParameter generic_parameter)
        {
            InitializeGenericConstraints();

            MetadataToken[] mapping;
            if (!metadata.TryGetGenericConstraintMapping(generic_parameter, out mapping))
                return false;

            return mapping.Length > 0;
        }

        public Collection<TypeReference> ReadGenericConstraints(GenericParameter generic_parameter)
        {
            InitializeGenericConstraints();

            MetadataToken[] mapping;
            if (!metadata.TryGetGenericConstraintMapping(generic_parameter, out mapping))
                return new Collection<TypeReference>();

            var constraints = new Collection<TypeReference>(mapping.Length);

            this.context = (IGenericContext)generic_parameter.Owner;

            for (int i = 0; i < mapping.Length; i++)
                constraints.Add(GetTypeDefOrRef(mapping[i]));

            metadata.RemoveGenericConstraintMapping(generic_parameter);

            return constraints;
        }

        void InitializeGenericConstraints()
        {
            if (metadata.GenericConstraints != null)
                return;

            var length = MoveTo(Table.GenericParamConstraint);

            metadata.GenericConstraints = new Dictionary<uint, MetadataToken[]>(length);

            for (int i = 1; i <= length; i++)
                AddGenericConstraintMapping(
                    ReadTableIndex(Table.GenericParam),
                    ReadMetadataToken(CodedIndex.TypeDefOrRef));
        }

        void AddGenericConstraintMapping(uint generic_parameter, MetadataToken constraint)
        {
            metadata.SetGenericConstraintMapping(
                generic_parameter,
                AddMapping(metadata.GenericConstraints, generic_parameter, constraint));
        }

        public bool HasOverrides(MethodDefinition method)
        {
            InitializeOverrides();
            MetadataToken[] mapping;

            if (!metadata.TryGetOverrideMapping(method, out mapping))
                return false;

            return mapping.Length > 0;
        }

        public Collection<MethodReference> ReadOverrides(MethodDefinition method)
        {
            InitializeOverrides();

            MetadataToken[] mapping;
            if (!metadata.TryGetOverrideMapping(method, out mapping))
                return new Collection<MethodReference>();

            var overrides = new Collection<MethodReference>(mapping.Length);

            this.context = method;

            for (int i = 0; i < mapping.Length; i++)
                overrides.Add((MethodReference)LookupToken(mapping[i]));

            metadata.RemoveOverrideMapping(method);

            return overrides;
        }

        void InitializeOverrides()
        {
            if (metadata.Overrides != null)
                return;

            var length = MoveTo(Table.MethodImpl);

            metadata.Overrides = new Dictionary<uint, MetadataToken[]>(length);

            for (int i = 1; i <= length; i++)
            {
                ReadTableIndex(Table.TypeDef);

                var method = ReadMetadataToken(CodedIndex.MethodDefOrRef);
                if (method.TokenType != TokenType.Method)
                    throw new NotSupportedException();

                var @override = ReadMetadataToken(CodedIndex.MethodDefOrRef);

                AddOverrideMapping(method.RID, @override);
            }
        }

        void AddOverrideMapping(uint method_rid, MetadataToken @override)
        {
            metadata.SetOverrideMapping(
                method_rid,
                AddMapping(metadata.Overrides, method_rid, @override));
        }

        public MethodBody ReadMethodBody(MethodDefinition method)
        {
            return code.ReadMethodBody(method);
        }

        public CallSite ReadCallSite(MetadataToken token)
        {
            if (!MoveTo(Table.StandAloneSig, token.RID))
                return null;

            var signature = ReadBlobIndex();

            var call_site = new CallSite();

            ReadMethodSignature(signature, call_site);

            call_site.MetadataToken = token;

            return call_site;
        }

        public VariableDefinitionCollection ReadVariables(MetadataToken local_var_token)
        {
            if (!MoveTo(Table.StandAloneSig, local_var_token.RID))
                return null;

            var reader = ReadSignature(ReadBlobIndex());
            const byte local_sig = 0x7;

            if (reader.ReadByte() != local_sig)
                throw new NotSupportedException();

            var count = reader.ReadCompressedUInt32();
            if (count == 0)
                return null;

            var variables = new VariableDefinitionCollection((int)count);

            for (int i = 0; i < count; i++)
                variables.Add(new VariableDefinition(reader.ReadTypeSignature()));

            return variables;
        }

        public IMetadataTokenProvider LookupToken(MetadataToken token)
        {
            var rid = token.RID;

            if (rid == 0)
                return null;

            IMetadataTokenProvider element;
            var position = this.position;
            var context = this.context;

            switch (token.TokenType)
            {
                case TokenType.TypeDef:
                    element = GetTypeDefinition(rid);
                    break;
                case TokenType.TypeRef:
                    element = GetTypeReference(rid);
                    break;
                case TokenType.TypeSpec:
                    element = GetTypeSpecification(rid);
                    break;
                case TokenType.Field:
                    element = GetFieldDefinition(rid);
                    break;
                case TokenType.Method:
                    element = GetMethodDefinition(rid);
                    break;
                case TokenType.MemberRef:
                    element = GetMemberReference(rid);
                    break;
                case TokenType.MethodSpec:
                    element = GetMethodSpecification(rid);
                    break;
                default:
                    return null;
            }

            this.position = position;
            this.context = context;

            return element;
        }

        public FieldDefinition GetFieldDefinition(uint rid)
        {
            InitializeTypeDefinitions();

            var field = metadata.GetFieldDefinition(rid);
            if (field != null)
                return field;

            return LookupField(rid);
        }

        FieldDefinition LookupField(uint rid)
        {
            var type = metadata.GetFieldDeclaringType(rid);
            if (type == null)
                return null;

            InitializeCollection(type.Fields);

            return metadata.GetFieldDefinition(rid);
        }

        public MethodDefinition GetMethodDefinition(uint rid)
        {
            InitializeTypeDefinitions();

            var method = metadata.GetMethodDefinition(rid);
            if (method != null)
                return method;

            return LookupMethod(rid);
        }

        MethodDefinition LookupMethod(uint rid)
        {
            var type = metadata.GetMethodDeclaringType(rid);
            if (type == null)
                return null;

            InitializeCollection(type.Methods);

            return metadata.GetMethodDefinition(rid);
        }

        MethodSpecification GetMethodSpecification(uint rid)
        {
            if (!MoveTo(Table.MethodSpec, rid))
                return null;

            var element_method = (MethodReference)LookupToken(
                ReadMetadataToken(CodedIndex.MethodDefOrRef));
            var signature = ReadBlobIndex();

            var method_spec = ReadMethodSpecSignature(signature, element_method);
            method_spec.token = new MetadataToken(TokenType.MethodSpec, rid);
            return method_spec;
        }

        MethodSpecification ReadMethodSpecSignature(uint signature, MethodReference method)
        {
            var reader = ReadSignature(signature);
            const byte methodspec_sig = 0x0a;

            var call_conv = reader.ReadByte();

            if (call_conv != methodspec_sig)
                throw new NotSupportedException();

            var instance = new GenericInstanceMethod(method);

            reader.ReadGenericInstanceSignature(method, instance);

            return instance;
        }

        MemberReference GetMemberReference(uint rid)
        {
            InitializeMemberReferences();

            var member = metadata.GetMemberReference(rid);
            if (member != null)
                return member;

            member = ReadMemberReference(rid);
            if (member != null && !member.ContainsGenericParameter)
                metadata.AddMemberReference(member);
            return member;
        }

        MemberReference ReadMemberReference(uint rid)
        {
            if (!MoveTo(Table.MemberRef, rid))
                return null;

            var token = ReadMetadataToken(CodedIndex.MemberRefParent);
            var name = ReadString();
            var signature = ReadBlobIndex();

            MemberReference member;

            switch (token.TokenType)
            {
                case TokenType.TypeDef:
                case TokenType.TypeRef:
                case TokenType.TypeSpec:
                    member = ReadTypeMemberReference(token, name, signature);
                    break;
                case TokenType.Method:
                    member = ReadMethodMemberReference(token, name, signature);
                    break;
                default:
                    throw new NotSupportedException();
            }

            member.token = new MetadataToken(TokenType.MemberRef, rid);

            return member;
        }

        MemberReference ReadTypeMemberReference(MetadataToken type, string name, uint signature)
        {
            var declaring_type = GetTypeDefOrRef(type);

            if (!declaring_type.IsArray)
                this.context = declaring_type;

            var member = ReadMemberReferenceSignature(signature, declaring_type);
            member.Name = name;

            return member;
        }

        MemberReference ReadMemberReferenceSignature(uint signature, TypeReference declaring_type)
        {
            var reader = ReadSignature(signature);
            const byte field_sig = 0x6;

            if (reader.buffer[reader.position] == field_sig)
            {
                reader.position++;
                var field = new FieldReference();
                field.DeclaringType = declaring_type;
                field.FieldType = reader.ReadTypeSignature();
                return field;
            }
            else
            {
                var method = new MethodReference();
                method.DeclaringType = declaring_type;
                reader.ReadMethodSignature(method);
                return method;
            }
        }

        MemberReference ReadMethodMemberReference(MetadataToken token, string name, uint signature)
        {
            var method = GetMethodDefinition(token.RID);

            this.context = method;

            var member = ReadMemberReferenceSignature(signature, method.DeclaringType);
            member.Name = name;

            return member;
        }

        void InitializeMemberReferences()
        {
            if (metadata.MemberReferences != null)
                return;

            metadata.MemberReferences = new MemberReference[image.GetTableLength(Table.MemberRef)];
        }

        public IEnumerable<MemberReference> GetMemberReferences()
        {
            InitializeMemberReferences();

            var length = image.GetTableLength(Table.MemberRef);

            var type_system = module.TypeSystem;

            var context = new MethodReference(string.Empty, type_system.Void);
            context.DeclaringType = new TypeReference(string.Empty, string.Empty, module, type_system.Corlib);

            var member_references = new MemberReference[length];

            for (uint i = 1; i <= length; i++)
            {
                this.context = context;
                member_references[i - 1] = GetMemberReference(i);
            }

            return member_references;
        }

        void InitializeConstants()
        {
            if (metadata.Constants != null)
                return;

            var length = MoveTo(Table.Constant);

            var constants = metadata.Constants = new Dictionary<MetadataToken, Row<ElementType, uint>>(length);

            for (uint i = 1; i <= length; i++)
            {
                var type = (ElementType)ReadUInt16();
                var owner = ReadMetadataToken(CodedIndex.HasConstant);
                var signature = ReadBlobIndex();

                constants.Add(owner, new Row<ElementType, uint>(type, signature));
            }
        }

        public object ReadConstant(IConstantProvider owner)
        {
            InitializeConstants();

            Row<ElementType, uint> row;
            if (!metadata.Constants.TryGetValue(owner.MetadataToken, out row))
                return Mixin.NoValue;

            metadata.Constants.Remove(owner.MetadataToken);

            switch (row.Col1)
            {
                case ElementType.Class:
                case ElementType.Object:
                    return null;
                case ElementType.String:
                    return ReadConstantString(ReadBlob(row.Col2));
                default:
                    return ReadConstantPrimitive(row.Col1, row.Col2);
            }
        }

        static string ReadConstantString(byte[] blob)
        {
            var length = blob.Length;
            if ((length & 1) == 1)
                length--;

            return Encoding.Unicode.GetString(blob, 0, length);
        }

        object ReadConstantPrimitive(ElementType type, uint signature)
        {
            var reader = ReadSignature(signature);
            return reader.ReadConstantSignature(type);
        }

        void InitializeCustomAttributes()
        {
            if (metadata.CustomAttributes != null)
                return;

            metadata.CustomAttributes = InitializeRanges(
                Table.CustomAttribute, () =>
                {
                    var next = ReadMetadataToken(CodedIndex.HasCustomAttribute);
                    ReadMetadataToken(CodedIndex.CustomAttributeType);
                    ReadBlobIndex();
                    return next;
                });
        }

        public bool HasCustomAttributes(ICustomAttributeProvider owner)
        {
            InitializeCustomAttributes();

            Range range;
            if (!metadata.TryGetCustomAttributeRange(owner, out range))
                return false;

            return range.Length > 0;
        }

        public Collection<CustomAttribute> ReadCustomAttributes(ICustomAttributeProvider owner)
        {
            InitializeCustomAttributes();

            Range range;
            if (!metadata.TryGetCustomAttributeRange(owner, out range)
                || !MoveTo(Table.CustomAttribute, range.Start))
                return new Collection<CustomAttribute>();

            var custom_attributes = new Collection<CustomAttribute>((int)range.Length);

            for (int i = 0; i < range.Length; i++)
            {
                ReadMetadataToken(CodedIndex.HasCustomAttribute);

                var constructor = (MethodReference)LookupToken(
                    ReadMetadataToken(CodedIndex.CustomAttributeType));

                var signature = ReadBlobIndex();

                custom_attributes.Add(new CustomAttribute(signature, constructor));
            }

            metadata.RemoveCustomAttributeRange(owner);

            return custom_attributes;
        }

        public byte[] ReadCustomAttributeBlob(uint signature)
        {
            return ReadBlob(signature);
        }

        public void ReadCustomAttributeSignature(CustomAttribute attribute)
        {
            var reader = ReadSignature(attribute.signature);

            if (!reader.CanReadMore())
                return;

            if (reader.ReadUInt16() != 0x0001)
                throw new InvalidOperationException();

            var constructor = attribute.Constructor;
            if (constructor.HasParameters)
                reader.ReadCustomAttributeConstructorArguments(attribute, constructor.Parameters);

            if (!reader.CanReadMore())
                return;

            var named = reader.ReadUInt16();

            if (named == 0)
                return;

            reader.ReadCustomAttributeNamedArguments(named, ref attribute.fields, ref attribute.properties);
        }

        void InitializeMarshalInfos()
        {
            if (metadata.FieldMarshals != null)
                return;

            var length = MoveTo(Table.FieldMarshal);

            var marshals = metadata.FieldMarshals = new Dictionary<MetadataToken, uint>(length);

            for (int i = 0; i < length; i++)
            {
                var token = ReadMetadataToken(CodedIndex.HasFieldMarshal);
                var signature = ReadBlobIndex();
                if (token.RID == 0)
                    continue;

                marshals.Add(token, signature);
            }
        }

        public bool HasMarshalInfo(IMarshalInfoProvider owner)
        {
            InitializeMarshalInfos();

            return metadata.FieldMarshals.ContainsKey(owner.MetadataToken);
        }

        public MarshalInfo ReadMarshalInfo(IMarshalInfoProvider owner)
        {
            InitializeMarshalInfos();

            uint signature;
            if (!metadata.FieldMarshals.TryGetValue(owner.MetadataToken, out signature))
                return null;

            var reader = ReadSignature(signature);

            metadata.FieldMarshals.Remove(owner.MetadataToken);

            return reader.ReadMarshalInfo();
        }

        void InitializeSecurityDeclarations()
        {
            if (metadata.SecurityDeclarations != null)
                return;

            metadata.SecurityDeclarations = InitializeRanges(
                Table.DeclSecurity, () =>
                {
                    ReadUInt16();
                    var next = ReadMetadataToken(CodedIndex.HasDeclSecurity);
                    ReadBlobIndex();
                    return next;
                });
        }

        public bool HasSecurityDeclarations(ISecurityDeclarationProvider owner)
        {
            InitializeSecurityDeclarations();

            Range range;
            if (!metadata.TryGetSecurityDeclarationRange(owner, out range))
                return false;

            return range.Length > 0;
        }

        public Collection<SecurityDeclaration> ReadSecurityDeclarations(ISecurityDeclarationProvider owner)
        {
            InitializeSecurityDeclarations();

            Range range;
            if (!metadata.TryGetSecurityDeclarationRange(owner, out range)
                || !MoveTo(Table.DeclSecurity, range.Start))
                return new Collection<SecurityDeclaration>();

            var security_declarations = new Collection<SecurityDeclaration>((int)range.Length);

            for (int i = 0; i < range.Length; i++)
            {
                var action = (SecurityAction)ReadUInt16();
                ReadMetadataToken(CodedIndex.HasDeclSecurity);
                var signature = ReadBlobIndex();

                security_declarations.Add(new SecurityDeclaration(action, signature, module));
            }

            metadata.RemoveSecurityDeclarationRange(owner);

            return security_declarations;
        }

        public byte[] ReadSecurityDeclarationBlob(uint signature)
        {
            return ReadBlob(signature);
        }

        public void ReadSecurityDeclarationSignature(SecurityDeclaration declaration)
        {
            var signature = declaration.signature;
            var reader = ReadSignature(signature);

            if (reader.buffer[reader.position] != '.')
            {
                ReadXmlSecurityDeclaration(signature, declaration);
                return;
            }

            reader.position++;
            var count = reader.ReadCompressedUInt32();
            var attributes = new Collection<SecurityAttribute>((int)count);

            for (int i = 0; i < count; i++)
                attributes.Add(reader.ReadSecurityAttribute());

            declaration.security_attributes = attributes;
        }

        void ReadXmlSecurityDeclaration(uint signature, SecurityDeclaration declaration)
        {
            var blob = ReadBlob(signature);
            var attributes = new Collection<SecurityAttribute>(1);

            var attribute = new SecurityAttribute(
                module.TypeSystem.LookupType("System.Security.Permissions", "PermissionSetAttribute"));

            attribute.properties = new Collection<CustomAttributeNamedArgument>(1);
            attribute.properties.Add(
                new CustomAttributeNamedArgument(
                    "XML",
                    new CustomAttributeArgument(
                        module.TypeSystem.String,
                        Encoding.Unicode.GetString(blob, 0, blob.Length))));

            attributes.Add(attribute);

            declaration.security_attributes = attributes;
        }

        public Collection<ExportedType> ReadExportedTypes()
        {
            var length = MoveTo(Table.ExportedType);
            if (length == 0)
                return new Collection<ExportedType>();

            var exported_types = new Collection<ExportedType>(length);

            for (int i = 1; i <= length; i++)
            {
                var attributes = (TypeAttributes)ReadUInt32();
                var identifier = ReadUInt32();
                var name = ReadString();
                var @namespace = ReadString();
                var implementation = ReadMetadataToken(CodedIndex.Implementation);

                ExportedType declaring_type = null;
                IMetadataScope scope = null;

                switch (implementation.TokenType)
                {
                    case TokenType.AssemblyRef:
                    case TokenType.File:
                        scope = GetExportedTypeScope(implementation);
                        break;
                    case TokenType.ExportedType:
                        // FIXME: if the table is not properly sorted
                        declaring_type = exported_types[(int)implementation.RID - 1];
                        break;
                }

                var exported_type = new ExportedType(@namespace, name, module, scope)
                {
                    Attributes = attributes,
                    Identifier = (int)identifier,
                    DeclaringType = declaring_type,
                };
                exported_type.token = new MetadataToken(TokenType.ExportedType, i);

                exported_types.Add(exported_type);
            }

            return exported_types;
        }

        IMetadataScope GetExportedTypeScope(MetadataToken token)
        {
            var position = this.position;
            IMetadataScope scope;

            switch (token.TokenType)
            {
                case TokenType.AssemblyRef:
                    InitializeAssemblyReferences();
                    scope = metadata.AssemblyReferences[(int)token.RID - 1];
                    break;
                case TokenType.File:
                    InitializeModuleReferences();
                    scope = GetModuleReferenceFromFile(token);
                    break;
                default:
                    throw new NotSupportedException();
            }

            this.position = position;
            return scope;
        }

        ModuleReference GetModuleReferenceFromFile(MetadataToken token)
        {
            if (!MoveTo(Table.File, token.RID))
                return null;

            ReadUInt32();
            var file_name = ReadString();
            var modules = module.ModuleReferences;

            ModuleReference reference;
            for (int i = 0; i < modules.Count; i++)
            {
                reference = modules[i];
                if (reference.Name == file_name)
                    return reference;
            }

            reference = new ModuleReference(file_name);
            modules.Add(reference);
            return reference;
        }

        static void InitializeCollection(object o)
        {
        }
    }

    sealed class SignatureReader : ByteBuffer
    {

        readonly MetadataReader reader;
        readonly uint start, sig_length;

        TypeSystem TypeSystem
        {
            get { return reader.module.TypeSystem; }
        }

        public SignatureReader(uint blob, MetadataReader reader)
            : base(reader.buffer)
        {
            this.reader = reader;

            MoveToBlob(blob);

            this.sig_length = ReadCompressedUInt32();
            this.start = (uint)position;
        }

        void MoveToBlob(uint blob)
        {
            position = (int)(reader.image.BlobHeap.Offset + blob);
        }

        MetadataToken ReadTypeTokenSignature()
        {
            return Mixin.GetMetadataToken(CodedIndex.TypeDefOrRef, ReadCompressedUInt32());
        }

        GenericParameter GetGenericParameter(GenericParameterType type, uint var)
        {
            var context = reader.context;
            int index = (int)var;

            if (context == null)
                return GetUnboundGenericParameter(type, index);

            IGenericParameterProvider provider;

            switch (type)
            {
                case GenericParameterType.Type:
                    provider = context.Type;
                    break;
                case GenericParameterType.Method:
                    provider = context.Method;
                    break;
                default:
                    throw new NotSupportedException();
            }

            if (!context.IsDefinition)
                CheckGenericContext(provider, index);

            if (index >= provider.GenericParameters.Count)
                return GetUnboundGenericParameter(type, index);

            return provider.GenericParameters[index];
        }

        GenericParameter GetUnboundGenericParameter(GenericParameterType type, int index)
        {
            return new GenericParameter(index, type, reader.module);
        }

        static void CheckGenericContext(IGenericParameterProvider owner, int index)
        {
            var owner_parameters = owner.GenericParameters;

            for (int i = owner_parameters.Count; i <= index; i++)
                owner_parameters.Add(new GenericParameter(owner));
        }

        public void ReadGenericInstanceSignature(IGenericParameterProvider provider, IGenericInstance instance)
        {
            var arity = ReadCompressedUInt32();

            if (!provider.IsDefinition)
                CheckGenericContext(provider, (int)arity - 1);

            var instance_arguments = instance.GenericArguments;

            for (int i = 0; i < arity; i++)
                instance_arguments.Add(ReadTypeSignature());
        }

        ArrayType ReadArrayTypeSignature()
        {
            var array = new ArrayType(ReadTypeSignature());

            var rank = ReadCompressedUInt32();

            var sizes = new uint[ReadCompressedUInt32()];
            for (int i = 0; i < sizes.Length; i++)
                sizes[i] = ReadCompressedUInt32();

            var low_bounds = new int[ReadCompressedUInt32()];
            for (int i = 0; i < low_bounds.Length; i++)
                low_bounds[i] = ReadCompressedInt32();

            array.Dimensions.Clear();

            for (int i = 0; i < rank; i++)
            {
                int? lower = null, upper = null;

                if (i < low_bounds.Length)
                    lower = low_bounds[i];

                if (i < sizes.Length)
                    upper = lower + (int)sizes[i] - 1;

                array.Dimensions.Add(new ArrayDimension(lower, upper));
            }

            return array;
        }

        TypeReference GetTypeDefOrRef(MetadataToken token)
        {
            return reader.GetTypeDefOrRef(token);
        }

        public TypeReference ReadTypeSignature()
        {
            return ReadTypeSignature((ElementType)ReadByte());
        }

        TypeReference ReadTypeSignature(ElementType etype)
        {
            switch (etype)
            {
                case ElementType.ValueType:
                    {
                        var value_type = GetTypeDefOrRef(ReadTypeTokenSignature());
                        value_type.IsValueType = true;
                        return value_type;
                    }
                case ElementType.Class:
                    return GetTypeDefOrRef(ReadTypeTokenSignature());
                case ElementType.Ptr:
                    return new PointerType(ReadTypeSignature());
                case ElementType.FnPtr:
                    {
                        var fptr = new FunctionPointerType();
                        ReadMethodSignature(fptr);
                        return fptr;
                    }
                case ElementType.ByRef:
                    return new ByReferenceType(ReadTypeSignature());
                case ElementType.Pinned:
                    return new PinnedType(ReadTypeSignature());
                case ElementType.SzArray:
                    return new ArrayType(ReadTypeSignature());
                case ElementType.Array:
                    return ReadArrayTypeSignature();
                case ElementType.CModOpt:
                    return new OptionalModifierType(
                        GetTypeDefOrRef(ReadTypeTokenSignature()), ReadTypeSignature());
                case ElementType.CModReqD:
                    return new RequiredModifierType(
                        GetTypeDefOrRef(ReadTypeTokenSignature()), ReadTypeSignature());
                case ElementType.Sentinel:
                    return new SentinelType(ReadTypeSignature());
                case ElementType.Var:
                    return GetGenericParameter(GenericParameterType.Type, ReadCompressedUInt32());
                case ElementType.MVar:
                    return GetGenericParameter(GenericParameterType.Method, ReadCompressedUInt32());
                case ElementType.GenericInst:
                    {
                        var is_value_type = ReadByte() == (byte)ElementType.ValueType;
                        var element_type = GetTypeDefOrRef(ReadTypeTokenSignature());
                        var generic_instance = new GenericInstanceType(element_type);

                        ReadGenericInstanceSignature(element_type, generic_instance);

                        if (is_value_type)
                        {
                            generic_instance.IsValueType = true;
                            element_type.GetElementType().IsValueType = true;
                        }

                        return generic_instance;
                    }
                case ElementType.Object: return TypeSystem.Object;
                case ElementType.Void: return TypeSystem.Void;
                case ElementType.TypedByRef: return TypeSystem.TypedReference;
                case ElementType.I: return TypeSystem.IntPtr;
                case ElementType.U: return TypeSystem.UIntPtr;
                default: return GetPrimitiveType(etype);
            }
        }

        public void ReadMethodSignature(IMethodSignature method)
        {
            var calling_convention = ReadByte();

            const byte has_this = 0x20;
            const byte explicit_this = 0x40;

            if ((calling_convention & has_this) != 0)
            {
                method.HasThis = true;
                calling_convention = (byte)(calling_convention & ~has_this);
            }

            if ((calling_convention & explicit_this) != 0)
            {
                method.ExplicitThis = true;
                calling_convention = (byte)(calling_convention & ~explicit_this);
            }

            method.CallingConvention = (MethodCallingConvention)calling_convention;

            var generic_context = method as MethodReference;
            if (generic_context != null && !generic_context.DeclaringType.IsArray)
                reader.context = generic_context;

            if ((calling_convention & 0x10) != 0)
            {
                var arity = ReadCompressedUInt32();

                if (generic_context != null && !generic_context.IsDefinition)
                    CheckGenericContext(generic_context, (int)arity - 1);
            }

            var param_count = ReadCompressedUInt32();

            method.MethodReturnType.ReturnType = ReadTypeSignature();

            if (param_count == 0)
                return;

            Collection<ParameterDefinition> parameters;

            var method_ref = method as MethodReference;
            if (method_ref != null)
                parameters = method_ref.parameters = new ParameterDefinitionCollection(method, (int)param_count);
            else
                parameters = method.Parameters;

            for (int i = 0; i < param_count; i++)
                parameters.Add(new ParameterDefinition(ReadTypeSignature()));
        }

        public object ReadConstantSignature(ElementType type)
        {
            return ReadPrimitiveValue(type);
        }

        public void ReadCustomAttributeConstructorArguments(CustomAttribute attribute, Collection<ParameterDefinition> parameters)
        {
            var count = parameters.Count;
            if (count == 0)
                return;

            attribute.arguments = new Collection<CustomAttributeArgument>(count);

            for (int i = 0; i < count; i++)
                attribute.arguments.Add(
                    ReadCustomAttributeFixedArgument(parameters[i].ParameterType));
        }

        CustomAttributeArgument ReadCustomAttributeFixedArgument(TypeReference type)
        {
            if (type.IsArray)
                return ReadCustomAttributeFixedArrayArgument((ArrayType)type);

            return ReadCustomAttributeElement(type);
        }

        public void ReadCustomAttributeNamedArguments(ushort count, ref Collection<CustomAttributeNamedArgument> fields, ref Collection<CustomAttributeNamedArgument> properties)
        {
            for (int i = 0; i < count; i++)
                ReadCustomAttributeNamedArgument(ref fields, ref properties);
        }

        void ReadCustomAttributeNamedArgument(ref Collection<CustomAttributeNamedArgument> fields, ref Collection<CustomAttributeNamedArgument> properties)
        {
            var kind = ReadByte();
            var type = ReadCustomAttributeFieldOrPropType();
            var name = ReadUTF8String();

            Collection<CustomAttributeNamedArgument> container;
            switch (kind)
            {
                case 0x53:
                    container = GetCustomAttributeNamedArgumentCollection(ref fields);
                    break;
                case 0x54:
                    container = GetCustomAttributeNamedArgumentCollection(ref properties);
                    break;
                default:
                    throw new NotSupportedException();
            }

            container.Add(new CustomAttributeNamedArgument(name, ReadCustomAttributeFixedArgument(type)));
        }

        static Collection<CustomAttributeNamedArgument> GetCustomAttributeNamedArgumentCollection(ref Collection<CustomAttributeNamedArgument> collection)
        {
            if (collection != null)
                return collection;

            return collection = new Collection<CustomAttributeNamedArgument>();
        }

        CustomAttributeArgument ReadCustomAttributeFixedArrayArgument(ArrayType type)
        {
            var length = ReadUInt32();

            if (length == 0xffffffff)
                return new CustomAttributeArgument(type, null);

            if (length == 0)
                return new CustomAttributeArgument(type, Empty<CustomAttributeArgument>.Array);

            var arguments = new CustomAttributeArgument[length];
            var element_type = type.ElementType;

            for (int i = 0; i < length; i++)
                arguments[i] = ReadCustomAttributeElement(element_type);

            return new CustomAttributeArgument(type, arguments);
        }

        CustomAttributeArgument ReadCustomAttributeElement(TypeReference type)
        {
            if (type.IsArray)
                return ReadCustomAttributeFixedArrayArgument((ArrayType)type);

            return new CustomAttributeArgument(
                type,
                type.etype == ElementType.Object
                    ? ReadCustomAttributeElement(ReadCustomAttributeFieldOrPropType())
                    : ReadCustomAttributeElementValue(type));
        }

        object ReadCustomAttributeElementValue(TypeReference type)
        {
            var etype = type.etype;

            switch (etype)
            {
                case ElementType.String:
                    return ReadUTF8String();
                case ElementType.None:
                    if (Mixin.IsTypeOf(type,"System", "Type"))
                        return ReadTypeReference();

                    return ReadCustomAttributeEnum(type);
                default:
                    return ReadPrimitiveValue(etype);
            }
        }

        object ReadPrimitiveValue(ElementType type)
        {
            switch (type)
            {
                case ElementType.Boolean:
                    return ReadByte() == 1;
                case ElementType.I1:
                    return (sbyte)ReadByte();
                case ElementType.U1:
                    return ReadByte();
                case ElementType.Char:
                    return (char)ReadUInt16();
                case ElementType.I2:
                    return ReadInt16();
                case ElementType.U2:
                    return ReadUInt16();
                case ElementType.I4:
                    return ReadInt32();
                case ElementType.U4:
                    return ReadUInt32();
                case ElementType.I8:
                    return ReadInt64();
                case ElementType.U8:
                    return ReadUInt64();
                case ElementType.R4:
                    return ReadSingle();
                case ElementType.R8:
                    return ReadDouble();
                default:
                    throw new NotImplementedException(type.ToString());
            }
        }

        TypeReference GetPrimitiveType(ElementType etype)
        {
            switch (etype)
            {
                case ElementType.Boolean:
                    return TypeSystem.Boolean;
                case ElementType.Char:
                    return TypeSystem.Char;
                case ElementType.I1:
                    return TypeSystem.SByte;
                case ElementType.U1:
                    return TypeSystem.Byte;
                case ElementType.I2:
                    return TypeSystem.Int16;
                case ElementType.U2:
                    return TypeSystem.UInt16;
                case ElementType.I4:
                    return TypeSystem.Int32;
                case ElementType.U4:
                    return TypeSystem.UInt32;
                case ElementType.I8:
                    return TypeSystem.Int64;
                case ElementType.U8:
                    return TypeSystem.UInt64;
                case ElementType.R4:
                    return TypeSystem.Single;
                case ElementType.R8:
                    return TypeSystem.Double;
                case ElementType.String:
                    return TypeSystem.String;
                default:
                    throw new NotImplementedException(etype.ToString());
            }
        }

        TypeReference ReadCustomAttributeFieldOrPropType()
        {
            var etype = (ElementType)ReadByte();

            switch (etype)
            {
                case ElementType.Boxed:
                    return TypeSystem.Object;
                case ElementType.SzArray:
                    return new ArrayType(ReadCustomAttributeFieldOrPropType());
                case ElementType.Enum:
                    return ReadTypeReference();
                case ElementType.Type:
                    return TypeSystem.LookupType("System", "Type");
                default:
                    return GetPrimitiveType(etype);
            }
        }

        public TypeReference ReadTypeReference()
        {
            return TypeParser.ParseType(reader.module, ReadUTF8String());
        }

        object ReadCustomAttributeEnum(TypeReference enum_type)
        {
            try
            {
                TypeDefinition type = null;
                type = Mixin.CheckedResolve(enum_type);
                if (!type.IsEnum)
                    throw new ArgumentException();
                return ReadCustomAttributeElementValue(Mixin.GetEnumUnderlyingType(type));
            }
            catch
            {
                //Resolve failed
                string name = enum_type.FullName + ", " + enum_type.scope.Name;
                Type type = Type.GetType(name);
                if (type == null || !type.IsEnum)
                    return new ArgumentException();
                var fields = type.GetFields(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Public);
                Type eType = null;
                foreach(var i in fields)
                {
                    eType = i.FieldType;
                    break;
                }

                object val;
                if(eType == typeof(int))
                {
                    val = ReadPrimitiveValue(ElementType.I4);
                }
                else if (eType == typeof(long))
                {
                    val = ReadPrimitiveValue(ElementType.I8);
                }
                else if (eType == typeof(short))
                {
                    val = ReadPrimitiveValue(ElementType.I2);
                }
                else if (eType == typeof(byte))
                {
                    val = ReadPrimitiveValue(ElementType.U1);
                }
                else if (eType == typeof(uint))
                {
                    val = ReadPrimitiveValue(ElementType.U4);
                }
                else if (eType == typeof(ulong))
                {
                    val = ReadPrimitiveValue(ElementType.U8);
                }
                else if (eType == typeof(ushort))
                {
                    val = ReadPrimitiveValue(ElementType.U2);
                }
                else
                {
                    val = ReadPrimitiveValue(ElementType.Void);
                }

                return Enum.ToObject(type, val);
            }
            
        }

        public SecurityAttribute ReadSecurityAttribute()
        {
            var attribute = new SecurityAttribute(ReadTypeReference());

            ReadCompressedUInt32();

            ReadCustomAttributeNamedArguments(
                (ushort)ReadCompressedUInt32(),
                ref attribute.fields,
                ref attribute.properties);

            return attribute;
        }

        public MarshalInfo ReadMarshalInfo()
        {
            var native = ReadNativeType();
            switch (native)
            {
                case NativeType.Array:
                    {
                        var array = new ArrayMarshalInfo();
                        if (CanReadMore())
                            array.element_type = ReadNativeType();
                        if (CanReadMore())
                            array.size_parameter_index = (int)ReadCompressedUInt32();
                        if (CanReadMore())
                            array.size = (int)ReadCompressedUInt32();
                        if (CanReadMore())
                            array.size_parameter_multiplier = (int)ReadCompressedUInt32();
                        return array;
                    }
                case NativeType.SafeArray:
                    {
                        var array = new SafeArrayMarshalInfo();
                        if (CanReadMore())
                            array.element_type = ReadVariantType();
                        return array;
                    }
                case NativeType.FixedArray:
                    {
                        var array = new FixedArrayMarshalInfo();
                        if (CanReadMore())
                            array.size = (int)ReadCompressedUInt32();
                        if (CanReadMore())
                            array.element_type = ReadNativeType();
                        return array;
                    }
                case NativeType.FixedSysString:
                    {
                        var sys_string = new FixedSysStringMarshalInfo();
                        if (CanReadMore())
                            sys_string.size = (int)ReadCompressedUInt32();
                        return sys_string;
                    }
                case NativeType.CustomMarshaler:
                    {
                        var marshaler = new CustomMarshalInfo();
                        var guid_value = ReadUTF8String();
                        marshaler.guid = !string.IsNullOrEmpty(guid_value) ? new Guid(guid_value) : Guid.Empty;
                        marshaler.unmanaged_type = ReadUTF8String();
                        marshaler.managed_type = ReadTypeReference();
                        marshaler.cookie = ReadUTF8String();
                        return marshaler;
                    }
                default:
                    return new MarshalInfo(native);
            }
        }

        NativeType ReadNativeType()
        {
            return (NativeType)ReadByte();
        }

        VariantType ReadVariantType()
        {
            return (VariantType)ReadByte();
        }

        string ReadUTF8String()
        {
            if (buffer[position] == 0xff)
            {
                position++;
                return null;
            }

            var length = (int)ReadCompressedUInt32();
            if (length == 0)
                return string.Empty;

            var @string = Encoding.UTF8.GetString(buffer, position,
                buffer[position + length - 1] == 0 ? length - 1 : length);

            position += length;
            return @string;
        }

        public bool CanReadMore()
        {
            return position - start < sig_length;
        }
    }
}