public PosixPageFileBackedMemoryMapPager(string file, long?initialFileSize = null)
{
var instanceId = Interlocked.Increment(ref _counter);
_file = "/" + Syscall.getpid() + "-" + instanceId + "-" + file;
_fd = Rt.shm_open(_file, OpenFlags.O_RDWR | OpenFlags.O_CREAT, (int)FilePermissions.ALLPERMS);
if (_fd == -1)
{
PosixHelper.ThrowLastError(Marshal.GetLastWin32Error());
}
SysPageSize = Syscall.sysconf(SysconfName._SC_PAGESIZE);
if (initialFileSize.HasValue)
{
_totalAllocationSize = NearestSizeToPageSize(initialFileSize.Value);
}
_totalAllocationSize = NearestSizeToPageSize(_totalAllocationSize);
var result = Syscall.ftruncate(_fd, _totalAllocationSize);
if (result != 0)
{
PosixHelper.ThrowLastError(result);
}
NumberOfAllocatedPages = _totalAllocationSize / PageSize;
PagerState.Release();
PagerState = CreatePagerState();
}
private PagerState CreatePagerState()
{
var startingBaseAddressPtr = Syscall.mmap(IntPtr.Zero, (ulong)_totalAllocationSize,
MmapProts.PROT_READ | MmapProts.PROT_WRITE,
MmapFlags.MAP_SHARED, _fd, 0);
if (startingBaseAddressPtr.ToInt64() == -1) //system didn't succeed in mapping the address where we wanted
{
PosixHelper.ThrowLastError(Marshal.GetLastWin32Error());
}
var allocationInfo = new PagerState.AllocationInfo
{
BaseAddress = (byte *)startingBaseAddressPtr.ToPointer(),
Size = _totalAllocationSize,
MappedFile = null
};
var newPager = new PagerState(this)
{
Files = null, // unused
MapBase = allocationInfo.BaseAddress,
AllocationInfos = new[] { allocationInfo }
};
newPager.AddRef(); // one for the pager
return(newPager);
}
public override void ReleaseAllocationInfo(byte *baseAddress, long size)
{
var result = Syscall.munmap(new IntPtr(baseAddress), (ulong)size);
if (result == -1)
{
PosixHelper.ThrowLastError(Marshal.GetLastWin32Error());
}
}