bool FileMapping::Map(int64 mapoffset, dword maplen)
{
	ASSERT(IsOpen());
	if(maplen == 0)
		return Unmap();
	mapoffset = minmax<int64>(mapoffset, 0, filesize);
	int gran = sMappingGranularity_();
	int64 rawoff = mapoffset & -gran;
	maplen = (dword)min<int64>(maplen, filesize - mapoffset);
	dword rawsz = (dword)min<int64>((maplen + (dword)(mapoffset - rawoff) + gran - 1) & -gran, filesize - rawoff);
	if(rawbase && (mapoffset < rawoffset || mapoffset + maplen > rawoffset + rawsize))
		Unmap();
	if(!rawbase) {
		rawoffset = rawoff;
		rawsize = rawsz;
#ifdef PLATFORM_WIN32
		rawbase = (byte *)MapViewOfFile(hmap, /*write ? FILE_MAP_WRITE :*/ FILE_MAP_READ,
			(dword)(rawoffset >> 32), (dword)(rawoffset >> 0), rawsize);
#else
		rawbase = (byte *)mmap(0, rawsize,
			PROT_READ | (write ? PROT_WRITE : 0),
#ifdef PLATFORM_FREEBSD
			MAP_NOSYNC,
#else
			MAP_SHARED,
#endif
			hfile, (dword)rawoffset);
#endif
#ifdef PLATFORM_POSIX
		if(rawbase == (byte *)~0)
#else
		if(!rawbase)
#endif
			return false;
	}
	offset = mapoffset;
	size = maplen;
	base = rawbase + (int)(offset - rawoffset);
	return true;
}