PetaJson/Topten.JsonKit/Emit.cs

// JsonKit v0.5 - A simple but flexible Json library in a single .cs file.
// 
// Copyright (C) 2014 Topten Software (contact@toptensoftware.com) All rights reserved.
// 
// Licensed under the Apache License, Version 2.0 (the "License"); you may not use this product 
// except in compliance with the License. You may obtain a copy of the License at
// 
// http://www.apache.org/licenses/LICENSE-2.0
// 
// Unless required by applicable law or agreed to in writing, software distributed under the 
// License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, 
// either express or implied. See the License for the specific language governing permissions 
// and limitations under the License.

#if !JSONKIT_NO_EMIT

using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Reflection;
using System.Globalization;
using System.Reflection.Emit;

namespace Topten.JsonKit
{
    static class Emit
    {

        // Generates a function that when passed an object of specified type, renders it to an IJsonWriter
        public static Action<IJsonWriter, object> MakeFormatter(Type type)
        {
            var formatJson = ReflectionInfo.FindFormatJson(type);
            if (formatJson != null)
            {
                var method = new DynamicMethod("invoke_formatJson", null, new Type[] { typeof(IJsonWriter), typeof(Object) }, true);
                var il = method.GetILGenerator();
                if (formatJson.ReturnType == typeof(string))
                {
                    // w.WriteStringLiteral(o.FormatJson())
                    il.Emit(OpCodes.Ldarg_0); 
                    il.Emit(OpCodes.Ldarg_1);
                    il.Emit(OpCodes.Unbox, type);
                    il.Emit(OpCodes.Call, formatJson);
                    il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteStringLiteral"));
                }
                else
                {
                    // o.FormatJson(w);
                    il.Emit(OpCodes.Ldarg_1);
                    il.Emit(type.IsValueType ? OpCodes.Unbox : OpCodes.Castclass, type);
                    il.Emit(OpCodes.Ldarg_0);
                    il.Emit(type.IsValueType ? OpCodes.Call : OpCodes.Callvirt, formatJson);
                }
                il.Emit(OpCodes.Ret);
                return (Action<IJsonWriter, object>)method.CreateDelegate(typeof(Action<IJsonWriter, object>));
            }
            else
            {
                // Get the reflection info for this type
                var ri = ReflectionInfo.GetReflectionInfo(type);
                if (ri == null)
                    return null;

                // Create a dynamic method that can do the work
                var method = new DynamicMethod("dynamic_formatter", null, new Type[] { typeof(IJsonWriter), typeof(object) }, true);
                var il = method.GetILGenerator();

                // Cast/unbox the target object and store in local variable
                var locTypedObj = il.DeclareLocal(type);
                il.Emit(OpCodes.Ldarg_1);
                il.Emit(type.IsValueType ? OpCodes.Unbox_Any : OpCodes.Castclass, type);
                il.Emit(OpCodes.Stloc, locTypedObj);

                // Get Invariant CultureInfo (since we'll probably be needing this)
                var locInvariant = il.DeclareLocal(typeof(IFormatProvider));
                il.Emit(OpCodes.Call, typeof(CultureInfo).GetProperty("InvariantCulture").GetGetMethod());
                il.Emit(OpCodes.Stloc, locInvariant);

                // These are the types we'll call .ToString(Culture.InvariantCulture) on
                var toStringTypes = new Type[] { 
                    typeof(int), typeof(uint), typeof(long), typeof(ulong), 
                    typeof(short), typeof(ushort), typeof(decimal), 
                    typeof(byte), typeof(sbyte)
                };

                // Theses types we also generate for
                var otherSupportedTypes = new Type[] {
                    typeof(double), typeof(float), typeof(string), typeof(char)
                };

                // Call IJsonWriting if implemented
                if (typeof(IJsonWriting).IsAssignableFrom(type))
                {
                    if (type.IsValueType)
                    {
                        il.Emit(OpCodes.Ldloca, locTypedObj);
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Call, type.GetInterfaceMap(typeof(IJsonWriting)).TargetMethods[0]);
                    }
                    else
                    {
                        il.Emit(OpCodes.Ldloc, locTypedObj);
                        il.Emit(OpCodes.Castclass, typeof(IJsonWriting));
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriting).GetMethod("OnJsonWriting", new Type[] { typeof(IJsonWriter) }));
                    }
                }

                // Process all members
                foreach (var m in ri.Members)
                {
                    // Dont save deprecated properties
                    if (m.Deprecated)
                    {
                        continue;
                    }

                    // Ignore write only properties
                    var pi = m.Member as PropertyInfo;
                    if (pi != null && pi.GetGetMethod(true) == null)
                    {
                        continue;
                    }

                    // Get the member type
                    var memberType = m.MemberType;

                    // Get the field/property value and store it in a local
                    LocalBuilder locValue = il.DeclareLocal(memberType);
                    il.Emit(type.IsValueType ? OpCodes.Ldloca : OpCodes.Ldloc, locTypedObj);
                    if (pi != null)
                    {
                        il.Emit(type.IsValueType ? OpCodes.Call : OpCodes.Callvirt, pi.GetGetMethod(true));
                    }
                    if (m.Member is FieldInfo fi)
                    {
                        il.Emit(OpCodes.Ldfld, fi);
                    }
                    il.Emit(OpCodes.Stloc, locValue);

                    // A label for early exit if not writing this member
                    Label lblFinishedMember = il.DefineLabel();

                    // Helper to generate IL to write the key
                    void EmitWriteKey()
                    {
                        // Write the Json key
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Ldstr, m.JsonKey);
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteKeyNoEscaping", new Type[] { typeof(string) }));
                    }

                    // Is it a nullable type?
                    var typeUnderlying = Nullable.GetUnderlyingType(memberType);
                    if (typeUnderlying != null)
                    {
                        // Define some labels
                        var lblHasValue = il.DefineLabel();

                        // Call HasValue
                        il.Emit(OpCodes.Ldloca, locValue);
                        il.Emit(OpCodes.Call, memberType.GetProperty("HasValue").GetGetMethod());
                        il.Emit(OpCodes.Brtrue, lblHasValue);

                        // HasValue returned false, so either omit the key entirely, or write it as "null"
                        if (!m.ExcludeIfNull)
                        {
                            // Write the key
                            EmitWriteKey();

                            // No value, write "null"
                            il.Emit(OpCodes.Ldarg_0);
                            il.Emit(OpCodes.Ldstr, "null");
                            il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteRaw", new Type[] { typeof(string) }));
                        }
                        il.Emit(OpCodes.Br_S, lblFinishedMember);

                        // Get it's value
                        il.MarkLabel(lblHasValue);
                        il.Emit(OpCodes.Ldloca, locValue);
                        il.Emit(OpCodes.Call, memberType.GetProperty("Value").GetGetMethod());

                        // Switch to the underlying type from here on
                        locValue = il.DeclareLocal(typeUnderlying);
                        il.Emit(OpCodes.Stloc, locValue);
                        memberType = typeUnderlying;
                    }
                    else
                    {
                        if (m.ExcludeIfNull && !type.IsValueType)
                        {
                            il.Emit(OpCodes.Ldloc, locValue);
                            il.Emit(OpCodes.Brfalse_S, lblFinishedMember);
                        }
                    }

                    if (m.ExcludeIfEquals != null)
                    {
                        il.Emit(OpCodes.Ldloc, locValue);
                        var targetValue = Convert.ChangeType(m.ExcludeIfEquals, m.MemberType);
                        LoadContantFromObject(il, targetValue);
                        il.Emit(OpCodes.Ceq);
                        il.Emit(OpCodes.Brtrue_S, lblFinishedMember);
                    }

                    // ToString()
                    if (toStringTypes.Contains(memberType))
                    {
                        EmitWriteKey();
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(memberType.IsValueType ? OpCodes.Ldloca : OpCodes.Ldloc, locValue);
                        il.Emit(OpCodes.Ldloc, locInvariant);
                        il.Emit(OpCodes.Call, memberType.GetMethod("ToString", new Type[] { typeof(IFormatProvider) }));
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteRaw", new Type[] { typeof(string) }));
                    }

                    // ToString("R")
                    else if (memberType == typeof(float) || memberType == typeof(double))
                    {
                        EmitWriteKey();
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(memberType.IsValueType ? OpCodes.Ldloca : OpCodes.Ldloc, locValue);
                        il.Emit(OpCodes.Ldstr, "R");
                        il.Emit(OpCodes.Ldloc, locInvariant);
                        il.Emit(OpCodes.Call, memberType.GetMethod("ToString", new Type[] { typeof(string), typeof(IFormatProvider) }));
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteRaw", new Type[] { typeof(string) }));
                    }

                    // String?
                    else if (memberType == typeof(string))
                    {
                        EmitWriteKey();
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Ldloc, locValue);
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteStringLiteral", new Type[] { typeof(string) }));
                    }

                    // Char?
                    else if (memberType == typeof(char))
                    {
                        EmitWriteKey();
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Ldloca, locValue);
                        il.Emit(OpCodes.Call, memberType.GetMethod("ToString", new Type[] { }));
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteStringLiteral", new Type[] { typeof(string) }));
                    }

                    // Bool?
                    else if (memberType == typeof(bool))
                    {
                        EmitWriteKey();
                        il.Emit(OpCodes.Ldarg_0);
                        var lblTrue = il.DefineLabel();
                        var lblCont = il.DefineLabel();
                        il.Emit(OpCodes.Ldloc, locValue);
                        il.Emit(OpCodes.Brtrue_S, lblTrue);
                        il.Emit(OpCodes.Ldstr, "false");
                        il.Emit(OpCodes.Br_S, lblCont);
                        il.MarkLabel(lblTrue);
                        il.Emit(OpCodes.Ldstr, "true");
                        il.MarkLabel(lblCont);
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteRaw", new Type[] { typeof(string) }));
                    }

                    // NB: We don't support DateTime as it's format can be changed

                    else
                    {
                        // Load writer
                        il.Emit(OpCodes.Ldarg_0);

                        // Load value
                        il.Emit(OpCodes.Ldloc, locValue);
                        if (memberType.IsValueType)
                            il.Emit(OpCodes.Box, memberType);

                        // Write the key and value
                        if (m.ExcludeIfEmpty)
                        {
                            il.Emit(OpCodes.Ldstr, m.JsonKey);
                            il.Emit(OpCodes.Call, typeof(Emit).GetMethod("WriteKeyAndValueCheckIfEmpty"));
                        }
                        else
                        {
                            EmitWriteKey();
                            il.Emit(OpCodes.Callvirt, typeof(IJsonWriter).GetMethod("WriteValue", new Type[] { typeof(object) }));
                        }
                    }

                    il.MarkLabel(lblFinishedMember);
                }

                // Call IJsonWritten
                if (typeof(IJsonWritten).IsAssignableFrom(type))
                {
                    if (type.IsValueType)
                    {
                        il.Emit(OpCodes.Ldloca, locTypedObj);
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Call, type.GetInterfaceMap(typeof(IJsonWritten)).TargetMethods[0]);
                    }
                    else
                    {
                        il.Emit(OpCodes.Ldloc, locTypedObj);
                        il.Emit(OpCodes.Castclass, typeof(IJsonWriting));
                        il.Emit(OpCodes.Ldarg_0);
                        il.Emit(OpCodes.Callvirt, typeof(IJsonWriting).GetMethod("OnJsonWritten", new Type[] { typeof(IJsonWriter) }));
                    }
                }

                // Done!
                il.Emit(OpCodes.Ret);
                var impl = (Action<IJsonWriter, object>)method.CreateDelegate(typeof(Action<IJsonWriter, object>));

                // Wrap it in a call to WriteDictionary
                return (w, obj) =>
                {
                    w.WriteDictionary(() =>
                    {
                        impl(w, obj);
                    });
                };
            }
        }

        static void LoadContantFromObject(ILGenerator il, object value)
        {
            switch (Type.GetTypeCode(value.GetType()))
            {
                case TypeCode.Boolean:
                    il.Emit(OpCodes.Ldc_I4, ((bool)value) ? 1 : 0);
                    break;

                case TypeCode.Char:
                case TypeCode.SByte:
                case TypeCode.Byte:
                case TypeCode.Int16:
                case TypeCode.UInt16:
                case TypeCode.Int32:
                case TypeCode.UInt32:
                    il.Emit(OpCodes.Ldc_I4, (int)value);
                    break;

                case TypeCode.Int64:
                case TypeCode.UInt64:
                    il.Emit(OpCodes.Ldc_I8, (long)value);
                    break;

                case TypeCode.Single:
                    il.Emit(OpCodes.Ldc_R4, (float)value);
                    break;

                case TypeCode.Double:
                    il.Emit(OpCodes.Ldc_R8, (double)value);
                    break;

                default:
                    throw new InvalidOperationException($"JsonKit doesn't support the type `{value.GetType().ToString()}` for ExcludeIfEquals");
            }
        }

        public static void WriteKeyAndValueCheckIfEmpty(IJsonWriter w, object o, string key)
        {
            if (o == null)
                return;

            // Check if empty
            if (o is System.Collections.IEnumerable e)
            {
                if (!e.GetEnumerator().MoveNext())
                    return;
            }

            w.WriteKeyNoEscaping(key);
            w.WriteValue(o);
        }

        // Pseudo box lets us pass a value type by reference.  Used during 
        // deserialization of value types.
        interface IPseudoBox
        {
            object GetValue();
        }
        [Obfuscation(Exclude = true, ApplyToMembers = true)]
        class PseudoBox<T> : IPseudoBox where T : struct
        {
            public T value = default(T);
            object IPseudoBox.GetValue() { return value; }
        }


        // Make a parser for value types
        public static Func<IJsonReader, Type, object> MakeParser(Type type)
        {
            System.Diagnostics.Debug.Assert(type.IsValueType);

            // ParseJson method?
            var parseJson = ReflectionInfo.FindParseJson(type);
            if (parseJson != null)
            {
                if (parseJson.GetParameters()[0].ParameterType == typeof(IJsonReader))
                {
                    var method = new DynamicMethod("invoke_ParseJson", typeof(Object), new Type[] { typeof(IJsonReader), typeof(Type) }, true);
                    var il = method.GetILGenerator();

                    il.Emit(OpCodes.Ldarg_0);
                    il.Emit(OpCodes.Call, parseJson);
                    il.Emit(OpCodes.Box, type);
                    il.Emit(OpCodes.Ret);
                    return (Func<IJsonReader,Type,object>)method.CreateDelegate(typeof(Func<IJsonReader,Type,object>));
                }
                else
                {
                    var method = new DynamicMethod("invoke_ParseJson", typeof(Object), new Type[] { typeof(string) }, true);
                    var il = method.GetILGenerator();

                    il.Emit(OpCodes.Ldarg_0);
                    il.Emit(OpCodes.Call, parseJson);
                    il.Emit(OpCodes.Box, type);
                    il.Emit(OpCodes.Ret);
                    var invoke = (Func<string, object>)method.CreateDelegate(typeof(Func<string, object>));

                    return (r, t) =>
                    {
                        if (r.GetLiteralKind() == LiteralKind.String)
                        {
                            var o = invoke(r.GetLiteralString());
                            r.NextToken();
                            return o;
                        }
                        throw new InvalidDataException(string.Format("Expected string literal for type {0}", type.FullName));
                    };
                }
            }
            else
            {
                // Get the reflection info for this type
                var ri = ReflectionInfo.GetReflectionInfo(type);
                if (ri == null)
                    return null;

                // We'll create setters for each property/field
                var setters = new Dictionary<string, Action<IJsonReader, object>>();

                // Store the value in a pseudo box until it's fully initialized
                var boxType = typeof(PseudoBox<>).MakeGenericType(type);

                // Process all members
                foreach (var m in ri.Members)
                {
                    // Ignore write only properties
                    var pi = m.Member as PropertyInfo;
                    var fi = m.Member as FieldInfo;
                    if (pi != null && pi.GetSetMethod(true) == null)
                    {
                        continue;
                    }

                    // Create a dynamic method that can do the work
                    var method = new DynamicMethod("dynamic_parser", null, new Type[] { typeof(IJsonReader), typeof(object) }, true);
                    var il = method.GetILGenerator();

                    // Load the target
                    il.Emit(OpCodes.Ldarg_1);
                    il.Emit(OpCodes.Castclass, boxType);
                    il.Emit(OpCodes.Ldflda, boxType.GetField("value"));

                    // Get the value
                    GenerateGetJsonValue(m, il);

                    // Assign it
                    if (pi != null)
                        il.Emit(OpCodes.Call, pi.GetSetMethod(true));
                    if (fi != null)
                        il.Emit(OpCodes.Stfld, fi);

                    // Done
                    il.Emit(OpCodes.Ret);

                    // Store in the map of setters
                    setters.Add(m.JsonKey, (Action<IJsonReader, object>)method.CreateDelegate(typeof(Action<IJsonReader, object>)));
                }

                // Create helpers to invoke the interfaces (this is painful but avoids having to really box 
                // the value in order to call the interface).
                Action<object, IJsonReader> invokeLoading = MakeInterfaceCall(type, typeof(IJsonLoading));
                Action<object, IJsonReader> invokeLoaded = MakeInterfaceCall(type, typeof(IJsonLoaded));
                Func<object, IJsonReader, string, bool> invokeField = MakeLoadFieldCall(type);

                // Create the parser
                Func<IJsonReader, Type, object> parser = (reader, Type) =>
                {
                    // Create pseudobox (ie: new PseudoBox<Type>)
                    var box = DecoratingActivator.CreateInstance(boxType);

                    // Call IJsonLoading
                    if (invokeLoading != null)
                        invokeLoading(box, reader);

                    // Read the dictionary
                    reader.ParseDictionary(key =>
                    {
                        // Call IJsonLoadField
                        if (invokeField != null && invokeField(box, reader, key))
                            return;

                        // Get a setter and invoke it if found
                        Action<IJsonReader, object> setter;
                        if (setters.TryGetValue(key, out setter))
                        {
                            setter(reader, box);
                        }
                    });

                    // IJsonLoaded
                    if (invokeLoaded != null)
                        invokeLoaded(box, reader);

                    // Return the value
                    return ((IPseudoBox)box).GetValue();
                };

                // Done
                return parser;
            }
        }

        // Helper to make the call to a PsuedoBox value's IJsonLoading or IJsonLoaded
        static Action<object, IJsonReader> MakeInterfaceCall(Type type, Type tItf)
        {
            // Interface supported?
            if (!tItf.IsAssignableFrom(type))
                return null;

            // Resolve the box type
            var boxType = typeof(PseudoBox<>).MakeGenericType(type);

            // Create method
            var method = new DynamicMethod("dynamic_invoke_" + tItf.Name, null, new Type[] { typeof(object), typeof(IJsonReader) }, true);
            var il = method.GetILGenerator();

            // Call interface method
            il.Emit(OpCodes.Ldarg_0);
            il.Emit(OpCodes.Castclass, boxType);
            il.Emit(OpCodes.Ldflda, boxType.GetField("value"));
            il.Emit(OpCodes.Ldarg_1);
            il.Emit(OpCodes.Call, type.GetInterfaceMap(tItf).TargetMethods[0]);
            il.Emit(OpCodes.Ret);

            // Done
            return (Action<object, IJsonReader>)method.CreateDelegate(typeof(Action<object, IJsonReader>));
        }

        // Similar to above but for IJsonLoadField
        static Func<object, IJsonReader, string, bool> MakeLoadFieldCall(Type type)
        {
            // Interface supported?
            var tItf = typeof(IJsonLoadField);
            if (!tItf.IsAssignableFrom(type))
                return null;

            // Resolve the box type
            var boxType = typeof(PseudoBox<>).MakeGenericType(type);

            // Create method
            var method = new DynamicMethod("dynamic_invoke_" + tItf.Name, typeof(bool), new Type[] { typeof(object), typeof(IJsonReader), typeof(string) }, true);
            var il = method.GetILGenerator();

            // Call interface method
            il.Emit(OpCodes.Ldarg_0);
            il.Emit(OpCodes.Castclass, boxType);
            il.Emit(OpCodes.Ldflda, boxType.GetField("value"));
            il.Emit(OpCodes.Ldarg_1);
            il.Emit(OpCodes.Ldarg_2);
            il.Emit(OpCodes.Call, type.GetInterfaceMap(tItf).TargetMethods[0]);
            il.Emit(OpCodes.Ret);

            // Done
            return (Func<object, IJsonReader, string, bool>)method.CreateDelegate(typeof(Func<object, IJsonReader, string, bool>));
        }

        // Create an "into parser" that can parse from IJsonReader into a reference type (ie: a class)
        public static Action<IJsonReader, object> MakeIntoParser(Type type)
        {
            System.Diagnostics.Debug.Assert(!type.IsValueType);

            // Get the reflection info for this type
            var ri = ReflectionInfo.GetReflectionInfo(type);
            if (ri == null)
                return null;

            // We'll create setters for each property/field
            var setters = new Dictionary<string, Action<IJsonReader, object>>();

            // Process all members
            foreach (var m in ri.Members)
            {
                // Ignore write only properties
                var pi = m.Member as PropertyInfo;
                var fi = m.Member as FieldInfo;
                if (pi != null && pi.GetSetMethod(true) == null)
                {
                    continue;
                }

                // Ignore read only properties that has KeepInstance attribute
                if (pi != null && pi.GetGetMethod(true) == null && m.KeepInstance)
                {
                    continue;
                }

                // Create a dynamic method that can do the work
                var method = new DynamicMethod("dynamic_parser", null, new Type[] { typeof(IJsonReader), typeof(object) }, true);
                var il = method.GetILGenerator();

                // Load the target
                il.Emit(OpCodes.Ldarg_1);
                il.Emit(OpCodes.Castclass, type);

                // Try to keep existing instance?
                if (m.KeepInstance)
                {
                    // Get existing existing instance
                    il.Emit(OpCodes.Dup);
                    if (pi != null)
                        il.Emit(OpCodes.Callvirt, pi.GetGetMethod(true));
                    else
                        il.Emit(OpCodes.Ldfld, fi);

                    var existingInstance = il.DeclareLocal(m.MemberType);
                    var lblExistingInstanceNull = il.DefineLabel();

                    // Keep a copy of the existing instance in a locale
                    il.Emit(OpCodes.Dup);
                    il.Emit(OpCodes.Stloc, existingInstance);

                    // Compare to null
                    il.Emit(OpCodes.Ldnull);
                    il.Emit(OpCodes.Ceq);
                    il.Emit(OpCodes.Brtrue_S, lblExistingInstanceNull);

                    il.Emit(OpCodes.Ldarg_0);                       // reader
                    il.Emit(OpCodes.Ldloc, existingInstance);       // into
                    il.Emit(OpCodes.Callvirt, typeof(IJsonReader).GetMethod("ParseInto", new Type[] { typeof(Object) }));

                    il.Emit(OpCodes.Pop);       // Clean up target left on stack (1)
                    il.Emit(OpCodes.Ret);

                    il.MarkLabel(lblExistingInstanceNull);
                }

                // Get the value from IJsonReader
                GenerateGetJsonValue(m, il);

                // Assign it
                if (pi != null)
                    il.Emit(OpCodes.Callvirt, pi.GetSetMethod(true));
                if (fi != null)
                    il.Emit(OpCodes.Stfld, fi);

                // Done
                il.Emit(OpCodes.Ret);

                // Store the handler in map
                setters.Add(m.JsonKey, (Action<IJsonReader, object>)method.CreateDelegate(typeof(Action<IJsonReader, object>)));
            }


            // Now create the parseInto delegate
            Action<IJsonReader, object> parseInto = (reader, obj) =>
            {
                // Call IJsonLoading
                var loading = obj as IJsonLoading;
                if (loading != null)
                    loading.OnJsonLoading(reader);

                // Cache IJsonLoadField
                var lf = obj as IJsonLoadField;

                // Read dictionary keys
                reader.ParseDictionary(key =>
                {
                    // Call IJsonLoadField
                    if (lf != null && lf.OnJsonField(reader, key))
                        return;

                    // Call setters
                    Action<IJsonReader, object> setter;
                    if (setters.TryGetValue(key, out setter))
                    {
                        setter(reader, obj);
                    }
                });

                // Call IJsonLoaded
                var loaded = obj as IJsonLoaded;
                if (loaded != null)
                    loaded.OnJsonLoaded(reader);
            };

            // Since we've created the ParseInto handler, we might as well register
            // as a Parse handler too.
            RegisterIntoParser(type, parseInto);

            // Done
            return parseInto;
        }

        // Registers a ParseInto handler as Parse handler that instantiates the object
        // and then parses into it.
        static void RegisterIntoParser(Type type, Action<IJsonReader, object> parseInto)
        {
            // Check type has a parameterless constructor
            var con = type.GetConstructor(BindingFlags.Instance | BindingFlags.Public | BindingFlags.NonPublic, null, new Type[0], null);
            if (con == null)
                return;

            // Create a dynamic method that can do the work
            var method = new DynamicMethod("dynamic_factory", typeof(object), new Type[] { typeof(IJsonReader), typeof(Action<IJsonReader, object>) }, true);
            var il = method.GetILGenerator();

            // Create the new object
            var locObj = il.DeclareLocal(typeof(object));
            il.Emit(OpCodes.Newobj, con);

            il.Emit(OpCodes.Dup);               // For return value

            il.Emit(OpCodes.Stloc, locObj);

            il.Emit(OpCodes.Ldarg_1);           // parseinto delegate
            il.Emit(OpCodes.Ldarg_0);           // IJsonReader
            il.Emit(OpCodes.Ldloc, locObj);     // new object instance
            il.Emit(OpCodes.Callvirt, typeof(Action<IJsonReader, object>).GetMethod("Invoke"));
            il.Emit(OpCodes.Ret);

            var factory = (Func<IJsonReader, Action<IJsonReader, object>, object>)method.CreateDelegate(typeof(Func<IJsonReader, Action<IJsonReader, object>, object>));

            Json.RegisterParser(type, (reader, type2) =>
            {
                return factory(reader, parseInto);
            });
        }

        // Generate the MSIL to retrieve a value for a particular field or property from a IJsonReader
        private static void GenerateGetJsonValue(JsonMemberInfo m, ILGenerator il)
        {
            Action<string> generateCallToHelper = helperName =>
            {
                // Call the helper
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Call, typeof(Emit).GetMethod(helperName, new Type[] { typeof(IJsonReader) }));

                // Move to next token
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Callvirt, typeof(IJsonReader).GetMethod("NextToken", new Type[] { }));
            };

            Type[] numericTypes = new Type[] { 
                typeof(int), typeof(uint), typeof(long), typeof(ulong), 
                typeof(short), typeof(ushort), typeof(decimal), 
                typeof(byte), typeof(sbyte), 
                typeof(double), typeof(float)
            };

            if (m.MemberType == typeof(string))
            {
                generateCallToHelper("GetLiteralString");
            }

            else if (m.MemberType == typeof(bool))
            {
                generateCallToHelper("GetLiteralBool");
            }

            else if (m.MemberType == typeof(char))
            {
                generateCallToHelper("GetLiteralChar");
            }

            else if (numericTypes.Contains(m.MemberType))
            {
                // Get raw number string
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Call, typeof(Emit).GetMethod("GetLiteralNumber", new Type[] { typeof(IJsonReader) }));

                // Convert to a string
                il.Emit(OpCodes.Call, typeof(CultureInfo).GetProperty("InvariantCulture").GetGetMethod());
                il.Emit(OpCodes.Call, m.MemberType.GetMethod("Parse", new Type[] { typeof(string), typeof(IFormatProvider) }));

                // 
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Callvirt, typeof(IJsonReader).GetMethod("NextToken", new Type[] { }));
            }

            else
            {
                il.Emit(OpCodes.Ldarg_0);
                il.Emit(OpCodes.Ldtoken, m.MemberType);
                il.Emit(OpCodes.Call, typeof(Type).GetMethod("GetTypeFromHandle", new Type[] { typeof(RuntimeTypeHandle) }));
                il.Emit(OpCodes.Callvirt, typeof(IJsonReader).GetMethod("Parse", new Type[] { typeof(Type) }));
                il.Emit(m.MemberType.IsValueType ? OpCodes.Unbox_Any : OpCodes.Castclass, m.MemberType);
            }
        }

        // Helper to fetch a literal bool from an IJsonReader
        [Obfuscation(Exclude = true)]
        public static bool GetLiteralBool(IJsonReader r)
        {
            switch (r.GetLiteralKind())
            {
                case LiteralKind.True:
                    return true;

                case LiteralKind.False:
                    return false;

                default:
                    throw new InvalidDataException("expected a boolean value");
            }
        }

        // Helper to fetch a literal character from an IJsonReader
        [Obfuscation(Exclude = true)]
        public static char GetLiteralChar(IJsonReader r)
        {
            if (r.GetLiteralKind() != LiteralKind.String)
                throw new InvalidDataException("expected a single character string literal");
            var str = r.GetLiteralString();
            if (str == null || str.Length != 1)
                throw new InvalidDataException("expected a single character string literal");

            return str[0];
        }

        // Helper to fetch a literal string from an IJsonReader
        [Obfuscation(Exclude = true)]
        public static string GetLiteralString(IJsonReader r)
        {
            switch (r.GetLiteralKind())
            {
                case LiteralKind.Null: return null;
                case LiteralKind.String: return r.GetLiteralString();
            }
            throw new InvalidDataException("expected a string literal");
        }

        // Helper to fetch a literal number from an IJsonReader (returns the raw string)
        [Obfuscation(Exclude = true)]
        public static string GetLiteralNumber(IJsonReader r)
        {
            switch (r.GetLiteralKind())
            {
                case LiteralKind.SignedInteger:
                case LiteralKind.UnsignedInteger:
                case LiteralKind.FloatingPoint:
                    return r.GetLiteralString();
            }
            throw new InvalidDataException("expected a numeric literal");
        }
    }
}

#endif