Mine

void *hook( void *func, void *newFunc )
{
	if ( (func is null) || (newFunc is null) )
	{
		throw new Exception( "null pointer passed as function" );
	}
	
	ubyte* startPtr = cast(ubyte *)func;
	uint codeLen; //length of our trampoline
	ubyte* jmpFunc; //our trampoline function
	ubyte[] jmpCode; //code that will be placed at the beginning of func
	
	
	while ( codeLen < 5 )
	{
		codeLen += instructionLen( startPtr + codeLen );
	}
	
	jmpFunc = cast(ubyte *)VirtualAlloc( null, codeLen+5, MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE );
	memcpy( jmpFunc, func, codeLen );
	jmpFunc[codeLen] = 0xE9;
	*cast(uint *)&jmpFunc[codeLen+1] = (cast(uint)func - cast(uint)jmpFunc) - 5;
	
	jmpCode = new ubyte[5];
	jmpCode[0] = 0xE9;
	*cast(uint *)&jmpCode[1] = (cast(uint)newFunc - cast(uint)func) - 5;

	uint oldProtection;
	VirtualProtect( func, codeLen, PAGE_EXECUTE_READWRITE, &oldProtection );
	memcpy( func, jmpCode.ptr, jmpCode.length );
	memset( func + jmpCode.length, 0x90, codeLen - jmpCode.length );
	VirtualProtect( func, codeLen, oldProtection, &oldProtection );
	
	return jmpFunc;
}