一直使用 MongoDb 的 Samus C#驱动。
其有一个缺陷，就是无法支持struct的读写。
但是一般数据都用Class包装，所以也没有太在意。
随着这些天尝试写入 KLineData 时，遇到了非常龌龊的问题。
KLineData这个Class内部有一个TICK[4] 这样一个数组,TICK是一个结构类型
Samus可以顺利的写入KLineData
但是读取时，立刻发生了异常。
查看内部实现，发现其用Emit做的ORM，代码如下：
1.创建Map
private ExtendedPropertiesMap CreateExtendedPropertiesMap(Type classType){
var extPropMember = _profile.FindExtendedPropertiesMember(classType);
if(extPropMember == null)
return null; return new ExtendedPropertiesMap(
extPropMember.Name,
extPropMember.GetReturnType(),
MemberReflectionOptimizer.GetGetter(extPropMember),
MemberReflectionOptimizer.GetSetter(extPropMember));
}
其中GetSetter代码如下
public static Action<object, object> GetSetter(MemberInfo memberInfo)
{
if(memberInfo == null)
throw new ArgumentNullException("memberInfo");
if(memberInfo.MemberType != MemberTypes.Field && memberInfo.MemberType != MemberTypes.Property)
throw new ArgumentException("Only fields and properties are supported.", "memberInfo"); if(memberInfo.MemberType == MemberTypes.Field)
return GetFieldSetter(memberInfo as FieldInfo); if(memberInfo.MemberType == MemberTypes.Property)
return GetPropertySetter(memberInfo as PropertyInfo); throw new InvalidOperationException("Can only create setters for fields or properties.");
}
我们关注其中的Field的Emit反射
public static Action<object, object> GetFieldSetter(FieldInfo fieldInfo)
{
if(fieldInfo == null)
throw new ArgumentNullException("fieldInfo"); var key = CreateKey(fieldInfo); Action<object, object> setter; lock (SyncObject)
{
if (SetterCache.TryGetValue(key, out setter))
return setter;
} if (fieldInfo.IsInitOnly || fieldInfo.IsLiteral)
throw new InvalidOperationException("Cannot create a setter for a readonly field."); var sourceType = fieldInfo.DeclaringType;
var method = new DynamicMethod("Set" + fieldInfo.Name, null, new[] {typeof (object), typeof (object)}, true);
var gen = method.GetILGenerator(); gen.Emit(OpCodes.Ldarg_0);
gen.Emit(OpCodes.Castclass, sourceType);
gen.Emit(OpCodes.Ldarg_1);
gen.Emit(OpCodes.Unbox_Any, fieldInfo.FieldType);
gen.Emit(OpCodes.Stfld, fieldInfo);
gen.Emit(OpCodes.Ret); setter = (Action<object, object>) method.CreateDelegate(typeof (Action<object, object>)); lock (SyncObject)
{
SetterCache[key] = setter;
} return setter;
}
gen.Emit(OpCodes.Ldarg_0); // 把参数0入栈
gen.Emit(OpCodes.Castclass, sourceType);//把参数0的类型转为sourceType : x as NewType
gen.Emit(OpCodes.Ldarg_1);// 把参数1入栈
gen.Emit(OpCodes.Unbox_Any, fieldInfo.FieldType);//把参数1的类型强制转换为FieldType: (NewType)x
gen.Emit(OpCodes.Stfld, fieldInfo);// SetField( 参数0，参数1 ）
gen.Emit(OpCodes.Ret);// 返回
以上代码有一个问题，就是要求参数0是Class,如果是Value是有异常的，即使可行也是没有意义的，因为ValueType是指传递
setter函数的设计模式(<object,object>) 天然就无法处理Value
解决办法:
public void AddProperty(string name, object value)
{
#region Original Codes
//var memberMap = _classMap.GetMemberMapFromAlias(name);
//if (memberMap != null)
// memberMap.SetValue(_instance, value);
//else if ((!_classMap.HasDiscriminator || _classMap.DiscriminatorAlias != name) && _extendedProperties != null)
// _extendedProperties.Add(name, value);
#endregion
#region norsd Codes
if(_bIsClass)
{
var memberMap = _classMap.GetMemberMapFromAlias(name);
if (memberMap != null)
memberMap.SetValue(_instance, value);
else if ((!_classMap.HasDiscriminator || _classMap.DiscriminatorAlias != name) && _extendedProperties != null)
_extendedProperties.Add(name, value);
}
else
{
_SetStructValue(name, ref _instance, value);
}
#endregion
}
注意_bIsClass就走原始流程，如果是Struct就走 _SetStructValue 流程
下面贴出整个类的代码
架构：
设置一个全局静态变量
readonly static System.Collections.Generic.Dictionary<System.Reflection.FieldInfo, SETSTVALUE> _s_dtStSetter = new Dictionary<System.Reflection.FieldInfo, SETSTVALUE>();
用于缓存SetStructValue函数
同时一个类私有变量readonly System.Collections.Generic.Dictionary<string, SETSTVALUE> _dtStSetter = new Dictionary<string, SETSTVALUE>();
用于快速在FieldInfo.Name -> SetStructValue
_CreateStSetter是动态创建函数
using System;using MongoDB.Configuration.Mapping.Model;
using System.Collections.Generic;namespace MongoDB.Serialization.Builders
{
internal class ConcreteClassMapBuilder : IObjectBuilder
{
private readonly IClassMap _classMap;
#region Original
//private readonly object _instance;
#endregion
#region norsd
//由于struct需要装箱拆箱,_instance无法设为Null
private object _instance = null;
#endregion
private readonly IDictionary<string, object> _extendedProperties; public ConcreteClassMapBuilder(IClassMap classMap)
{
_classMap = classMap;
_instance = classMap.CreateInstance(); #region norsd
_bIsClass = _instance.GetType().IsClass;
if (!_bIsClass)
{
var fields = _instance.GetType().GetFields(System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.Public);
foreach (var fi in fields)
{
SETSTVALUE setter = null;
_s_dtStSetter.TryGetValue(fi, out setter);
if(setter == null)
{
setter = _CreateStSetter(_instance.GetType(),fi);
if(null == setter)
continue;
_s_dtStSetter.Add(fi, setter);
}
_dtStSetter.Add(fi.Name, setter);
}
}
#endregion if(!_classMap.HasExtendedProperties)
return; var extPropType = _classMap.ExtendedPropertiesMap.MemberReturnType;
if (extPropType == typeof(IDictionary<string, object>))
extPropType = typeof(Dictionary<string, object>);
_extendedProperties = (IDictionary<string, object>)Activator.CreateInstance(extPropType);
_classMap.ExtendedPropertiesMap.SetValue(_instance, _extendedProperties); } public void AddProperty(string name, object value)
{
#region Original Codes
//var memberMap = _classMap.GetMemberMapFromAlias(name);
//if (memberMap != null)
// memberMap.SetValue(_instance, value);
//else if ((!_classMap.HasDiscriminator || _classMap.DiscriminatorAlias != name) && _extendedProperties != null)
// _extendedProperties.Add(name, value);
#endregion
#region norsd Codes
if(_bIsClass)
{
var memberMap = _classMap.GetMemberMapFromAlias(name);
if (memberMap != null)
memberMap.SetValue(_instance, value);
else if ((!_classMap.HasDiscriminator || _classMap.DiscriminatorAlias != name) && _extendedProperties != null)
_extendedProperties.Add(name, value);
}
else
{
_SetStructValue(name, ref _instance, value);
}
#endregion
} public object BuildObject()
{
return _instance;
} public PropertyDescriptor GetPropertyDescriptor(string name)
{
var memberMap = _classMap.GetMemberMapFromAlias(name);
if (memberMap == null)
return null; var type = memberMap.MemberReturnType;
var isDictionary = false;
if (memberMap is CollectionMemberMap)
type = ((CollectionMemberMap)memberMap).ElementType;
else if (memberMap is DictionaryMemberMap)
{
type = ((DictionaryMemberMap)memberMap).ValueType;
isDictionary = true;
} return new PropertyDescriptor { Type = type, IsDictionary = isDictionary };
} #region norsd
delegate void SETSTVALUE(ref object instance, object value);
void _SetStructValue(string arg_strName , ref object arg_rInstance , object value)
{
SETSTVALUE setter = null;
_dtStSetter.TryGetValue(arg_strName ,out setter);
if (setter == null)
{
//throw new NotImplementedException();
}
else
{
setter(ref arg_rInstance, value);
}
}
SETSTVALUE _CreateStSetter(Type arg_sourceType, System.Reflection.FieldInfo arg_fieldinfo)
{
var sourceType = arg_sourceType;
var fieldInfo = arg_fieldinfo;
var method2 = new System.Reflection.Emit.DynamicMethod("Set" + fieldInfo.Name, null, new[] { typeof(object).MakeByRefType(), typeof(object) }, true);
var g = method2.GetILGenerator();
var local = g.DeclareLocal(sourceType, true);
g.Emit(System.Reflection.Emit.OpCodes.Ldarg_0);
g.Emit(System.Reflection.Emit.OpCodes.Ldind_Ref);
g.Emit(System.Reflection.Emit.OpCodes.Unbox_Any, sourceType);
g.Emit(System.Reflection.Emit.OpCodes.Stloc_0);//将前面Load的数据Set到Local 0
g.Emit(System.Reflection.Emit.OpCodes.Ldloca_S, local);
g.Emit(System.Reflection.Emit.OpCodes.Ldarg_1);
g.Emit(System.Reflection.Emit.OpCodes.Unbox_Any, fieldInfo.FieldType);
g.Emit(System.Reflection.Emit.OpCodes.Stfld, fieldInfo);
g.Emit(System.Reflection.Emit.OpCodes.Ldarg_0);
g.Emit(System.Reflection.Emit.OpCodes.Ldloc_0);
g.Emit(System.Reflection.Emit.OpCodes.Box, sourceType);
g.Emit(System.Reflection.Emit.OpCodes.Stind_Ref);
g.Emit(System.Reflection.Emit.OpCodes.Ret); var setter = (SETSTVALUE)method2.CreateDelegate(typeof(SETSTVALUE));
return setter;
}
bool _bIsClass = false;
readonly System.Collections.Generic.Dictionary<string, SETSTVALUE> _dtStSetter = new Dictionary<string, SETSTVALUE>();
//全局缓存,
readonly static System.Collections.Generic.Dictionary<System.Reflection.FieldInfo, SETSTVALUE> _s_dtStSetter = new Dictionary<System.Reflection.FieldInfo, SETSTVALUE>();
#endregion
}
}
