#include "stdafx.h"
#include <cstdint>
#include <process.h>
#include "OSVersion.h"

extern "C"
{
	extern void* TrapTableFirst;
	extern FARPROC alias__imp__IsDebuggerPresent;
	extern FARPROC alias__imp__EncodePointer;
	extern FARPROC alias__imp__DecodePointer;
	extern FARPROC alias__imp__HeapSetInformation;
	extern FARPROC alias__imp__InitializeCriticalSectionAndSpinCount;
	extern FARPROC alias__imp__InterlockedCompareExchange;
	extern FARPROC alias__imp__IsProcessorFeaturePresent;
	extern FARPROC alias__imp__InterlockedPushEntrySList;
	extern FARPROC alias__imp__InterlockedPopEntrySList;
	extern void* TrapTableLast;
} // extern "C"

namespace {

HMODULE GetKernelModule()
{
	static HMODULE hmodKernel;
	if (hmodKernel == nullptr)
	{
		hmodKernel = GetModuleHandle(TEXT("kernel32"));
	}
	return hmodKernel;
}

BOOL WINAPI Alternative_IsDebuggerPresent()
{
	::SetLastError(ERROR_NOT_SUPPORTED);
	return FALSE;
}

void* WINAPI Alternative_EncodePointer(void* p)
{
	return reinterpret_cast<void*>(reinterpret_cast<std::uintptr_t>(p) ^ __security_cookie);
}

#define Alternative_DecodePointer Alternative_EncodePointer

BOOL WINAPI Alternative_HeapSetInformation(HANDLE hHeap, HEAP_INFORMATION_CLASS hic, void* information, SSIZE_T informationLength)
{
	return TRUE;
}

#pragma warning(push)
#pragma warning(disable: 6320 6322)
BOOL WINAPI Alternative_InitializeCriticalSectionAndSpinCount(LPCRITICAL_SECTION lpcs, DWORD spinCount)
{
	__try
	{
		::InitializeCriticalSection(lpcs);
		return TRUE;
	}
	__except(EXCEPTION_EXECUTE_HANDLER)
	{
	}
	return FALSE;
}
#pragma warning(pop)

__declspec(naked) long __stdcall Alternative_InterlockedCompareExchange(long volatile*, long, long)
{
	__asm
	{
		mov             ecx,[esp+4]
		mov             edx,[esp+8]
		mov             eax,[esp+12]
		lock cmpxchg    [ecx],edx
		ret             12
	}
}

BOOL WINAPI Alternative_IsProcessorFeaturePresent(DWORD /*feture*/)
{
	// ATLからfeture = PF_NX_ENABLEDで呼ばれる
	return FALSE;
}

#define FUNCTION_INIT(name) \
	if (auto f = ::GetProcAddress(GetKernelModule(), #name)) { \
		alias__imp__ ## name = f; \
	} else { \
		alias__imp__ ## name = reinterpret_cast<FARPROC>(Alternative_ ## name); \
	}

void InitializeOldWindowsHelper()
{
	DWORD oldProtect;
	::VirtualProtect(&TrapTableFirst,
		reinterpret_cast<std::uintptr_t>(&TrapTableLast) - reinterpret_cast<std::uintptr_t>(&TrapTableFirst),
		PAGE_READWRITE, &oldProtect);
	FUNCTION_INIT(IsDebuggerPresent);
	FUNCTION_INIT(EncodePointer);
	FUNCTION_INIT(DecodePointer);
	FUNCTION_INIT(HeapSetInformation);
	alias__imp__InitializeCriticalSectionAndSpinCount = 
		ActiveBasic::Common::Is9x()
		? reinterpret_cast<FARPROC>(Alternative_InitializeCriticalSectionAndSpinCount)
		: ::GetProcAddress(GetKernelModule(), "InitializeCriticalSectionAndSpinCount");
	FUNCTION_INIT(InterlockedCompareExchange);
	FUNCTION_INIT(IsProcessorFeaturePresent);
	alias__imp__InterlockedPushEntrySList = ::GetProcAddress(GetKernelModule(), "InterlockedPushEntrySList");
	alias__imp__InterlockedPopEntrySList = ::GetProcAddress(GetKernelModule(), "InterlockedPopEntrySList");

	::VirtualProtect(&TrapTableFirst,
		reinterpret_cast<std::uintptr_t>(&TrapTableLast) - reinterpret_cast<std::uintptr_t>(&TrapTableFirst),
		PAGE_READONLY, &oldProtect);
}

} // unnamed namespace

extern "C"
{
#ifdef _UNICODE
int wWinMainCRTStartup();
#define tWinMainCRTStartup wWinMainCRTStartup
#else
int WinMainCRTStartup();
#define tWinMainCRTStartup WinMainCRTStartup
#endif

void WinMainStartup_OldWindowsHelper()
{
	__security_init_cookie();

	InitializeOldWindowsHelper();

	__asm
	{
		jmp	tWinMainCRTStartup;
	}
}

} // extern "C"