public static IComparer Compile( AssemblyEmitter assembly, Type objectType, Property[] props )
{
TypeBuilder typeBuilder = assembly.DefineType(
"__distinct",
TypeAttributes.Public,
typeof( object )
);
#region Constructor
{
ConstructorBuilder ctor = typeBuilder.DefineConstructor(
MethodAttributes.Public,
CallingConventions.Standard,
Type.EmptyTypes
);
ILGenerator il = ctor.GetILGenerator();
// : base()
il.Emit( OpCodes.Ldarg_0 );
il.Emit( OpCodes.Call, typeof( object ).GetConstructor( Type.EmptyTypes ) );
// return;
il.Emit( OpCodes.Ret );
}
#endregion
#region IComparer
typeBuilder.AddInterfaceImplementation( typeof( IComparer ) );
MethodBuilder compareMethod;
#region Compare
{
MethodEmitter emitter = new MethodEmitter( typeBuilder );
emitter.Define(
/* name */ "Compare",
/* attr */ MethodAttributes.Public | MethodAttributes.Virtual,
/* return */ typeof( int ),
/* params */ new Type[] { typeof( object ), typeof( object ) } );
LocalBuilder a = emitter.CreateLocal( objectType );
LocalBuilder b = emitter.CreateLocal( objectType );
LocalBuilder v = emitter.CreateLocal( typeof( int ) );
emitter.LoadArgument( 1 );
emitter.CastAs( objectType );
emitter.StoreLocal( a );
emitter.LoadArgument( 2 );
emitter.CastAs( objectType );
emitter.StoreLocal( b );
emitter.Load( 0 );
emitter.StoreLocal( v );
Label end = emitter.CreateLabel();
for ( int i = 0; i < props.Length; ++i )
{
if ( i > 0 )
{
emitter.LoadLocal( v );
emitter.BranchIfTrue( end ); // if ( v != 0 ) return v;
}
Property prop = props[i];
emitter.LoadLocal( a );
emitter.Chain( prop );
bool couldCompare =
emitter.CompareTo( 1, delegate()
{
emitter.LoadLocal( b );
emitter.Chain( prop );
} );
if ( !couldCompare )
throw new InvalidOperationException( "Property is not comparable." );
emitter.StoreLocal( v );
}
emitter.MarkLabel( end );
emitter.LoadLocal( v );
emitter.Return();
typeBuilder.DefineMethodOverride(
emitter.Method,
typeof( IComparer ).GetMethod(
"Compare",
new Type[]
{
typeof( object ),
typeof( object )
}
)
);
compareMethod = emitter.Method;
}
#endregion
#endregion
#region IEqualityComparer
typeBuilder.AddInterfaceImplementation( typeof( IEqualityComparer<object> ) );
#region Equals
{
MethodEmitter emitter = new MethodEmitter( typeBuilder );
emitter.Define(
/* name */ "Equals",
/* attr */ MethodAttributes.Public | MethodAttributes.Virtual,
/* return */ typeof( bool ),
/* params */ new Type[] { typeof( object ), typeof( object ) } );
emitter.Generator.Emit( OpCodes.Ldarg_0 );
emitter.Generator.Emit( OpCodes.Ldarg_1 );
emitter.Generator.Emit( OpCodes.Ldarg_2 );
emitter.Generator.Emit( OpCodes.Call, compareMethod );
emitter.Generator.Emit( OpCodes.Ldc_I4_0 );
emitter.Generator.Emit( OpCodes.Ceq );
emitter.Generator.Emit( OpCodes.Ret );
typeBuilder.DefineMethodOverride(
emitter.Method,
typeof( IEqualityComparer<object> ).GetMethod(
"Equals",
new Type[]
{
typeof( object ),
typeof( object )
}
)
);
}
#endregion
#region GetHashCode
{
MethodEmitter emitter = new MethodEmitter( typeBuilder );
emitter.Define(
/* name */ "GetHashCode",
/* attr */ MethodAttributes.Public | MethodAttributes.Virtual,
/* return */ typeof( int ),
/* params */ new Type[] { typeof( object ) } );
LocalBuilder obj = emitter.CreateLocal( objectType );
emitter.LoadArgument( 1 );
emitter.CastAs( objectType );
emitter.StoreLocal( obj );
for ( int i = 0; i < props.Length; ++i )
{
Property prop = props[i];
emitter.LoadLocal( obj );
emitter.Chain( prop );
Type active = emitter.Active;
MethodInfo getHashCode = active.GetMethod( "GetHashCode", Type.EmptyTypes );
if ( getHashCode == null )
getHashCode = typeof( object ).GetMethod( "GetHashCode", Type.EmptyTypes );
if ( active != typeof( int ) )
{
if ( !active.IsValueType )
{
LocalBuilder value = emitter.AcquireTemp( active );
Label valueNotNull = emitter.CreateLabel();
Label done = emitter.CreateLabel();
emitter.StoreLocal( value );
emitter.LoadLocal( value );
emitter.BranchIfTrue( valueNotNull );
emitter.Load( 0 );
emitter.Pop( typeof( int ) );
emitter.Branch( done );
emitter.MarkLabel( valueNotNull );
emitter.LoadLocal( value );
emitter.Call( getHashCode );
emitter.ReleaseTemp( value );
emitter.MarkLabel( done );
}
else
{
emitter.Call( getHashCode );
}
}
if ( i > 0 )
emitter.Xor();
}
emitter.Return();
typeBuilder.DefineMethodOverride(
emitter.Method,
typeof( IEqualityComparer<object> ).GetMethod(
"GetHashCode",
new Type[]
{
typeof( object )
}
)
);
}
#endregion
#endregion
Type comparerType = typeBuilder.CreateType();
return (IComparer) Activator.CreateInstance( comparerType );
}