public static MemoryMappedFile CreateFromFile(string path, FileMode mode, string mapName, long capacity,
MemoryMappedFileAccess access)
{
if (path == null)
{
throw new ArgumentNullException(nameof(path));
}
if (mapName != null && mapName.Length == 0)
{
throw new ArgumentException(SR.Argument_MapNameEmptyString);
}
if (capacity < 0)
{
throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_PositiveOrDefaultCapacityRequired);
}
if (access < MemoryMappedFileAccess.ReadWrite ||
access > MemoryMappedFileAccess.ReadWriteExecute)
{
throw new ArgumentOutOfRangeException(nameof(access));
}
if (mode == FileMode.Append)
{
throw new ArgumentException(SR.Argument_NewMMFAppendModeNotAllowed, nameof(mode));
}
if (access == MemoryMappedFileAccess.Write)
{
throw new ArgumentException(SR.Argument_NewMMFWriteAccessNotAllowed, nameof(access));
}
bool existed = File.Exists(path);
FileStream fileStream = new FileStream(path, mode, GetFileAccess(access), FileShare.Read, 0x1000, FileOptions.None);
if (capacity == 0 && fileStream.Length == 0)
{
CleanupFile(fileStream, existed, path);
throw new ArgumentException(SR.Argument_EmptyFile);
}
if (access == MemoryMappedFileAccess.Read && capacity > fileStream.Length)
{
CleanupFile(fileStream, existed, path);
throw new ArgumentException(SR.Argument_ReadAccessWithLargeCapacity);
}
if (capacity == DefaultSize)
{
capacity = fileStream.Length;
}
// one can always create a small view if they do not want to map an entire file
if (fileStream.Length > capacity)
{
CleanupFile(fileStream, existed, path);
throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_CapacityGEFileSizeRequired);
}
SafeMemoryMappedFileHandle handle = null;
try
{
handle = CreateCore(fileStream, mapName, HandleInheritability.None,
access, MemoryMappedFileOptions.None, capacity);
}
catch
{
CleanupFile(fileStream, existed, path);
throw;
}
Debug.Assert(handle != null);
Debug.Assert(!handle.IsInvalid);
return(new MemoryMappedFile(handle, fileStream, false));
}
public static MemoryMappedFile CreateFromFile(FileStream fileStream, string mapName, long capacity,
MemoryMappedFileAccess access,
HandleInheritability inheritability, bool leaveOpen)
{
if (fileStream == null)
{
throw new ArgumentNullException(nameof(fileStream), SR.ArgumentNull_FileStream);
}
if (mapName != null && mapName.Length == 0)
{
throw new ArgumentException(SR.Argument_MapNameEmptyString);
}
if (capacity < 0)
{
throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_PositiveOrDefaultCapacityRequired);
}
if (capacity == 0 && fileStream.Length == 0)
{
throw new ArgumentException(SR.Argument_EmptyFile);
}
if (access < MemoryMappedFileAccess.ReadWrite ||
access > MemoryMappedFileAccess.ReadWriteExecute)
{
throw new ArgumentOutOfRangeException(nameof(access));
}
if (access == MemoryMappedFileAccess.Write)
{
throw new ArgumentException(SR.Argument_NewMMFWriteAccessNotAllowed, nameof(access));
}
if (access == MemoryMappedFileAccess.Read && capacity > fileStream.Length)
{
throw new ArgumentException(SR.Argument_ReadAccessWithLargeCapacity);
}
if (inheritability < HandleInheritability.None || inheritability > HandleInheritability.Inheritable)
{
throw new ArgumentOutOfRangeException(nameof(inheritability));
}
// flush any bytes written to the FileStream buffer so that we can see them in our MemoryMappedFile
fileStream.Flush();
if (capacity == DefaultSize)
{
capacity = fileStream.Length;
}
// one can always create a small view if they do not want to map an entire file
if (fileStream.Length > capacity)
{
throw new ArgumentOutOfRangeException(nameof(capacity), SR.ArgumentOutOfRange_CapacityGEFileSizeRequired);
}
SafeMemoryMappedFileHandle handle = CreateCore(fileStream, mapName, inheritability,
access, MemoryMappedFileOptions.None, capacity);
return(new MemoryMappedFile(handle, fileStream, leaveOpen));
}
public unsafe static MemoryMappedView CreateView(SafeMemoryMappedFileHandle memMappedFileHandle,
MemoryMappedFileAccess access, long offset, long size)
{
// MapViewOfFile can only create views that start at a multiple of the system memory allocation
// granularity. We decided to hide this restriction from the user by creating larger views than the
// user requested and hiding the parts that the user did not request. extraMemNeeded is the amount of
// extra memory we allocate before the start of the requested view. MapViewOfFile will also round the
// capacity of the view to the nearest multiple of the system page size. Once again, we hide this
// from the user by preventing them from writing to any memory that they did not request.
ulong nativeSize;
long extraMemNeeded, newOffset;
ValidateSizeAndOffset(
size, offset, GetSystemPageAllocationGranularity(),
out nativeSize, out extraMemNeeded, out newOffset);
// if request is >= than total virtual, then MapViewOfFile will fail with meaningless error message
// "the parameter is incorrect"; this provides better error message in advance
Interop.mincore.MEMORYSTATUSEX memStatus;
memStatus.dwLength = (uint)sizeof(Interop.mincore.MEMORYSTATUSEX);
Interop.mincore.GlobalMemoryStatusEx(out memStatus);
ulong totalVirtual = memStatus.ullTotalVirtual;
if (nativeSize >= totalVirtual)
{
throw new IOException(SR.IO_NotEnoughMemory);
}
// split the long into two ints
int offsetLow = unchecked ((int)(newOffset & 0x00000000FFFFFFFFL));
int offsetHigh = unchecked ((int)(newOffset >> 32));
// create the view
SafeMemoryMappedViewHandle viewHandle = Interop.mincore.MapViewOfFile(memMappedFileHandle,
(int)MemoryMappedFile.GetFileMapAccess(access), offsetHigh, offsetLow, new UIntPtr(nativeSize));
if (viewHandle.IsInvalid)
{
viewHandle.Dispose();
throw Win32Marshal.GetExceptionForLastWin32Error();
}
// Query the view for its size and allocation type
Interop.mincore.MEMORY_BASIC_INFORMATION viewInfo = new Interop.mincore.MEMORY_BASIC_INFORMATION();
Interop.mincore.VirtualQuery(viewHandle, ref viewInfo, (UIntPtr)Marshal.SizeOf(viewInfo));
ulong viewSize = (ulong)viewInfo.RegionSize;
// Allocate the pages if we were using the MemoryMappedFileOptions.DelayAllocatePages option
// OR check if the allocated view size is smaller than the expected native size
// If multiple overlapping views are created over the file mapping object, the pages in a given region
// could have different attributes(MEM_RESERVE OR MEM_COMMIT) as MapViewOfFile preserves coherence between
// views created on a mapping object backed by same file.
// In which case, the viewSize will be smaller than nativeSize required and viewState could be MEM_COMMIT
// but more pages may need to be committed in the region.
// This is because, VirtualQuery function(that internally invokes VirtualQueryEx function) returns the attributes
// and size of the region of pages with matching attributes starting from base address.
// VirtualQueryEx: http://msdn.microsoft.com/en-us/library/windows/desktop/aa366907(v=vs.85).aspx
if (((viewInfo.State & Interop.mincore.MemOptions.MEM_RESERVE) != 0) || ((ulong)viewSize < (ulong)nativeSize))
{
IntPtr tempHandle = Interop.mincore.VirtualAlloc(
viewHandle, (UIntPtr)(nativeSize != MemoryMappedFile.DefaultSize ? nativeSize : viewSize),
Interop.mincore.MemOptions.MEM_COMMIT, MemoryMappedFile.GetPageAccess(access));
int lastError = Marshal.GetLastWin32Error();
if (viewHandle.IsInvalid)
{
viewHandle.Dispose();
throw Win32Marshal.GetExceptionForWin32Error(lastError);
}
// again query the view for its new size
viewInfo = new Interop.mincore.MEMORY_BASIC_INFORMATION();
Interop.mincore.VirtualQuery(viewHandle, ref viewInfo, (UIntPtr)Marshal.SizeOf(viewInfo));
viewSize = (ulong)viewInfo.RegionSize;
}
// if the user specified DefaultSize as the size, we need to get the actual size
if (size == MemoryMappedFile.DefaultSize)
{
size = (long)(viewSize - (ulong)extraMemNeeded);
}
else
{
Debug.Assert(viewSize >= (ulong)size, "viewSize < size");
}
viewHandle.Initialize((ulong)size + (ulong)extraMemNeeded);
return(new MemoryMappedView(viewHandle, extraMemNeeded, size, access));
}
