ld58/code/os/impl/windows/filesystem.c

OS_Handle FS_FileOpen(Str8 path, FS_AccessFlags access) {
	OS_Handle result = { 0 };

	M_TempScope(0, 0) {
		Str8 wpath = Win32_WideStr(temp.arena, path);

		DWORD dwAccess = 0;
		DWORD dwShare  = FILE_SHARE_READ;
		DWORD dwCreate = OPEN_EXISTING;

		if (access & FS_ACCESS_WRITE) {
			dwCreate = CREATE_ALWAYS;
			dwAccess = GENERIC_WRITE;
		}

		if (access & FS_ACCESS_READ) {
			dwAccess |= GENERIC_READ;
		}

		HANDLE hFile = CreateFileW((LPCWSTR) wpath.data, dwAccess, dwShare, 0, dwCreate, 0, 0);

		result.v[0] = (hFile == INVALID_HANDLE_VALUE) ? 0 : ((U64) hFile);
	}
	return result;
}

void FS_FileClose(OS_Handle file) {
	HANDLE hFile = cast(HANDLE) file.v[0];
	if (hFile) {
		CloseHandle(hFile);
	}
}

void FS_FileRead(OS_Handle file, void *ptr, U64 size, U64 offset) {
	HANDLE hFile = cast(HANDLE) file.v[0];
	if (hFile) {
		U8 *buffer    = ptr;
		U64 current   = offset;
		U64 remainder = size;

		while (remainder != 0) {
			OVERLAPPED overlapped = { 0 };
			overlapped.Offset     = cast(DWORD) (current & 0xFFFFFFFF);
			overlapped.OffsetHigh = cast(DWORD) ((current >> 32) & 0xFFFFFFFF);

			DWORD toread = (remainder > U32_MAX) ? U32_MAX : (DWORD) remainder;
			DWORD nread  = 0;

			if (!ReadFile(hFile, buffer, toread, &nread, &overlapped)) {
				break;
			}

			buffer    += nread;
			current   += nread;
			remainder -= nread;
		}
	}
}

void FS_FileWrite(OS_Handle file, void *ptr, U64 size, U64 offset) {
	HANDLE hFile = cast(HANDLE) file.v[0];
	if (hFile) {
		U8 *buffer    = ptr;
		U64 current   = offset;
		U64 remainder = size;

		while (remainder != 0) {
			OVERLAPPED overlapped = { 0 };
			overlapped.Offset     = cast(DWORD) (current & 0xFFFFFFFF);
			overlapped.OffsetHigh = cast(DWORD) ((current >> 32) & 0xFFFFFFFF);

			DWORD towrite  = (remainder > U32_MAX) ? U32_MAX : (DWORD) remainder;
			DWORD nwritten = 0;

			if (!WriteFile(hFile, buffer, towrite, &nwritten, &overlapped)) {
				break;
			}

			buffer    += nwritten;
			current   += nwritten;
			remainder -= nwritten;
		}
	}
}