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Removed use of intermediate buffering when reading from the cache

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svn path=/trunk/; revision=1503
This commit is contained in:
David Welch 2001-01-13 12:40:21 +00:00
parent e371c33d76
commit d2b9b6d912
1 changed files with 14 additions and 27 deletions
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37
reactos/drivers/fs/vfat/rw.c
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@ -1,5 +1,5 @@
/* $Id: rw.c,v 1.15 2001/01/12 21:00:08 dwelch Exp $
/* $Id: rw.c,v 1.16 2001/01/13 12:40:21 dwelch Exp $
*
* COPYRIGHT: See COPYING in the top level directory
* PROJECT: ReactOS kernel
@ -270,7 +270,9 @@ VfatReadCluster(PDEVICE_EXTENSION DeviceExt,
ULONG FirstCluster,
PULONG CurrentCluster,
PVOID Destination,
ULONG Cached)
ULONG Cached,
ULONG InternalOffset,
ULONG InternalLength)
{
ULONG BytesPerCluster;
BOOLEAN Valid;
@ -310,7 +312,7 @@ VfatReadCluster(PDEVICE_EXTENSION DeviceExt,
/*
* Copy the data from the cache to the caller
*/
memcpy(Destination, BaseAddress, BytesPerCluster);
memcpy(Destination, BaseAddress + InternalOffset, InternalLength);
CcReleaseCacheSegment(Fcb->RFCB.Bcb, CacheSeg, TRUE);
Status = NextCluster(DeviceExt, FirstCluster, CurrentCluster);
@ -381,7 +383,7 @@ VfatReadCluster(PDEVICE_EXTENSION DeviceExt,
/*
* Copy the data from the cache to the caller
*/
memcpy(Destination, BaseAddress + InternalOffset, BytesPerCluster);
memcpy(Destination, BaseAddress + InternalOffset, InternalLength);
CcReleaseCacheSegment(Fcb->RFCB.Bcb, CacheSeg, TRUE);
}
return(STATUS_SUCCESS);
@ -398,10 +400,9 @@ VfatReadFile (PDEVICE_EXTENSION DeviceExt, PFILE_OBJECT FileObject,
ULONG CurrentCluster;
ULONG FirstCluster;
PVFATFCB Fcb;
PVOID Temp;
ULONG TempLength;
ULONG ChunkSize;
NTSTATUS Status;
ULONG TempLength;
/* PRECONDITION */
assert (DeviceExt != NULL);
@ -445,15 +446,6 @@ VfatReadFile (PDEVICE_EXTENSION DeviceExt, PFILE_OBJECT FileObject,
*LengthRead = 0;
/*
* Allocate a buffer to hold partial clusters
*/
Temp = ExAllocatePool (NonPagedPool, ChunkSize);
if (!Temp)
{
return(STATUS_NO_MEMORY);
}
/*
* Find the cluster to start the read from
* FIXME: Optimize by remembering the last cluster read and using if
@ -472,12 +464,11 @@ VfatReadFile (PDEVICE_EXTENSION DeviceExt, PFILE_OBJECT FileObject,
*/
if ((ReadOffset % ChunkSize) != 0)
{
TempLength = min (Length, ChunkSize - (ReadOffset % ChunkSize));
VfatReadCluster(DeviceExt, Fcb,
ROUND_DOWN(ReadOffset, ChunkSize),
FirstCluster, &CurrentCluster, Temp, 1);
TempLength = min (Length, ChunkSize - (ReadOffset % ChunkSize));
memcpy (Buffer, Temp + ReadOffset % ChunkSize, TempLength);
FirstCluster, &CurrentCluster, Buffer, 1,
ReadOffset % ChunkSize, TempLength);
(*LengthRead) = (*LengthRead) + TempLength;
Length = Length - TempLength;
@ -488,10 +479,9 @@ VfatReadFile (PDEVICE_EXTENSION DeviceExt, PFILE_OBJECT FileObject,
while (Length >= ChunkSize)
{
VfatReadCluster(DeviceExt, Fcb, ReadOffset,
FirstCluster, &CurrentCluster, Buffer, 1);
FirstCluster, &CurrentCluster, Buffer, 1, 0, ChunkSize);
if (CurrentCluster == 0xffffffff)
{
ExFreePool (Temp);
return (STATUS_SUCCESS);
}
@ -500,15 +490,12 @@ VfatReadFile (PDEVICE_EXTENSION DeviceExt, PFILE_OBJECT FileObject,
Length = Length - ChunkSize;
ReadOffset = ReadOffset + ChunkSize;
}
if (Length > 0)
{
VfatReadCluster(DeviceExt, Fcb, ReadOffset,
FirstCluster, &CurrentCluster, Temp, 1);
FirstCluster, &CurrentCluster, Buffer, 1, 0, Length);
(*LengthRead) = (*LengthRead) + Length;
memcpy (Buffer, Temp, Length);
}
ExFreePool (Temp);
return (STATUS_SUCCESS);
}