internal static SafeMapViewHandle MapViewOfFile(
SafeMapHandle hMap, long fileOffset, long mapViewSize,
FileMapAccess desiredAccess)
{
if (hMap == null || hMap.IsInvalid)
{
throw new ArgumentNullException("hMap");
}
if (fileOffset < 0)
{
throw new ArgumentOutOfRangeException("fileOffset", fileOffset, "Must be >= 0");
}
if (mapViewSize <= 0)
{
throw new ArgumentOutOfRangeException("mapViewSize", mapViewSize, "Must be > 0");
}
return
(ThrowOnError(
MapViewOfFile(
hMap,
desiredAccess,
(uint)((fileOffset >> 32) & 0xFFFFFFFF),
(uint)(fileOffset & 0xFFFFFFFF),
(IntPtr)mapViewSize)));
}
private static extern SafeMapViewHandle MapViewOfFile(
SafeMapHandle hFileMappingObject,
FileMapAccess dwDesiredAccess,
uint dwFileOffsetHigh,
uint dwFileOffsetLow,
IntPtr dwNumberOfBytesToMap);
private int ProcessMemoryMappedFile(long firstItemIdx, ArraySegment <T> buffer, bool isWriting, long fileSize)
{
SafeMapHandle hMap = null;
try
{
bool isAligned;
long fileCount = CalculateItemCountFromFilePosition(fileSize, out isAligned);
if (!isAligned && isWriting)
{
throw new BinaryFileException(
"Cannot write to a file when its length does not align to item size ({0})",
ToString());
}
long idxToStopAt = firstItemIdx + buffer.Count;
if (!isWriting && idxToStopAt > fileCount)
{
idxToStopAt = fileCount;
}
long offsetToStopAt = ItemIdxToOffset(idxToStopAt);
long idxCurrent = firstItemIdx;
// Grow file if needed
if (isWriting && offsetToStopAt > fileSize)
{
fileSize = offsetToStopAt;
}
hMap = NativeWinApis.CreateFileMapping(
(FileStream)BaseStream, fileSize,
isWriting ? FileMapProtection.PageReadWrite : FileMapProtection.PageReadOnly);
while (idxCurrent < idxToStopAt)
{
SafeMapViewHandle ptrMapViewBaseAddr = null;
try
{
long offsetCurrent = ItemIdxToOffset(idxCurrent);
long mapViewFileOffset = Utils.RoundDownToMultiple(offsetCurrent, MinPageSize);
long mapViewSize = offsetToStopAt - mapViewFileOffset;
long itemsToProcessThisRun = idxToStopAt - idxCurrent;
if (mapViewSize > MaxLargePageSize)
{
mapViewSize = MaxLargePageSize;
itemsToProcessThisRun = (mapViewFileOffset + mapViewSize) / ItemSize - idxCurrent -
CalculateHeaderSizeAsItemCount();
}
// The size of the new map view.
ptrMapViewBaseAddr = NativeWinApis.MapViewOfFile(
hMap, mapViewFileOffset, mapViewSize,
isWriting ? FileMapAccess.Write : FileMapAccess.Read);
long totalItemsDone = idxCurrent - firstItemIdx;
long bufItemOffset = buffer.Offset + totalItemsDone;
// Access file using memory-mapped pages
Serializer.ProcessMemoryPtr(
(IntPtr)(ptrMapViewBaseAddr.Address + offsetCurrent - mapViewFileOffset),
new ArraySegment <T>(buffer.Array, (int)bufItemOffset, (int)itemsToProcessThisRun),
isWriting);
idxCurrent += itemsToProcessThisRun;
}
finally
{
if (ptrMapViewBaseAddr != null)
{
ptrMapViewBaseAddr.Dispose();
}
}
}
return((int)(idxCurrent - firstItemIdx));
}
finally
{
if (hMap != null)
{
hMap.Dispose();
}
}
}