[hbelusca] 68604: [NTVDM]: - Use a static buffer for read or writes of "few" bytes (and allocate one for larger operations). - Writes of zero length, in DOS, truncates or extends the file to the cu...

Author: hbelusca
Date: Thu Aug  6 01:32:38 2015
New Revision: 68604

URL: http://svn.reactos.org/svn/reactos?rev=68604&view=rev
Log:
[NTVDM]:
- Use a static buffer for read or writes of "few" bytes (and allocate one for
larger operations).
- Writes of zero length, in DOS, truncates or extends the file to the current position of
the file pointer. This fixes some "corruption" in some files (so far, only .INI
files) in Windows 3.11 installation.

Modified:
    trunk/reactos/subsystems/mvdm/ntvdm/dos/dos32krnl/dosfiles.c

Modified: trunk/reactos/subsystems/mvdm/ntvdm/dos/dos32krnl/dosfiles.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/subsystems/mvdm/ntvdm/dos/…
==============================================================================
--- trunk/reactos/subsystems/mvdm/ntvdm/dos/dos32krnl/dosfiles.c	[iso-8859-1] (original)
+++ trunk/reactos/subsystems/mvdm/ntvdm/dos/dos32krnl/dosfiles.c	[iso-8859-1] Thu Aug  6
01:32:38 2015
@@ -676,6 +676,7 @@
 {
     WORD Result = ERROR_SUCCESS;
     PDOS_FILE_DESCRIPTOR Descriptor = DosGetHandleFileDescriptor(FileHandle);
+    BYTE StaticBuffer[8192];
 
     DPRINT("DosReadFile: FileHandle 0x%04X, Count 0x%04X\n", FileHandle,
Count);
 
@@ -697,10 +698,19 @@
     else
     {
         DWORD BytesRead32 = 0;
-        LPVOID LocalBuffer = RtlAllocateHeap(RtlGetProcessHeap(), 0, Count);
-        ASSERT(LocalBuffer != NULL);
-
-        /* Read the file */
+        LPVOID LocalBuffer;
+
+        if (Count <= sizeof(StaticBuffer))
+        {
+            LocalBuffer = StaticBuffer;
+        }
+        else
+        {
+            LocalBuffer = RtlAllocateHeap(RtlGetProcessHeap(), 0, Count);
+            ASSERT(LocalBuffer != NULL);
+        }
+
+        /* Read from the file */
         if (ReadFile(Descriptor->Win32Handle, LocalBuffer, Count, &BytesRead32,
NULL))
         {
             /* Write to the memory */
@@ -710,7 +720,7 @@
                                 LOWORD(BytesRead32));
 
             /* Update the position */
-            Descriptor->Position += BytesRead32;
+            Descriptor->Position += BytesRead32; // or LOWORD(BytesRead32); ?
         }
         else
         {
@@ -720,7 +730,9 @@
 
         /* The number of bytes read is always 16-bit */
         *BytesRead = LOWORD(BytesRead32);
-        RtlFreeHeap(RtlGetProcessHeap(), 0, LocalBuffer);
+
+        if (LocalBuffer != StaticBuffer)
+            RtlFreeHeap(RtlGetProcessHeap(), 0, LocalBuffer);
     }
 
     /* Return the error code */
@@ -734,6 +746,7 @@
 {
     WORD Result = ERROR_SUCCESS;
     PDOS_FILE_DESCRIPTOR Descriptor = DosGetHandleFileDescriptor(FileHandle);
+    BYTE StaticBuffer[8192];
 
     DPRINT("DosWriteFile: FileHandle 0x%04X, Count 0x%04X\n", FileHandle,
Count);
 
@@ -755,21 +768,44 @@
     else
     {
         DWORD BytesWritten32 = 0;
-        LPVOID LocalBuffer = RtlAllocateHeap(RtlGetProcessHeap(), 0, Count);
-        ASSERT(LocalBuffer != NULL);
+        LPVOID LocalBuffer;
+
+        /*
+         * Writing zero bytes truncates or extends the file
+         * to the current position of the file pointer.
+         */
+        if (Count == 0)
+        {
+            if (!SetEndOfFile(Descriptor->Win32Handle))
+            {
+                /* Store the error code */
+                Result = (WORD)GetLastError();
+            }
+            *BytesWritten = 0;
+            return Result;
+        }
+
+        if (Count <= sizeof(StaticBuffer))
+        {
+            LocalBuffer = StaticBuffer;
+        }
+        else
+        {
+            LocalBuffer = RtlAllocateHeap(RtlGetProcessHeap(), 0, Count);
+            ASSERT(LocalBuffer != NULL);
+        }
 
         /* Read from the memory */
         EmulatorReadMemory(&EmulatorContext,
-                           TO_LINEAR(HIWORD(Buffer),
-                           LOWORD(Buffer)),
+                           TO_LINEAR(HIWORD(Buffer), LOWORD(Buffer)),
                            LocalBuffer,
                            Count);
 
-        /* Write the file */
+        /* Write to the file */
         if (WriteFile(Descriptor->Win32Handle, LocalBuffer, Count,
&BytesWritten32, NULL))
         {
             /* Update the position and size */
-            Descriptor->Position += BytesWritten32;
+            Descriptor->Position += BytesWritten32; // or LOWORD(BytesWritten32); ?
             if (Descriptor->Position > Descriptor->Size) Descriptor->Size =
Descriptor->Position;
         }
         else
@@ -780,7 +816,9 @@
 
         /* The number of bytes written is always 16-bit */
         *BytesWritten = LOWORD(BytesWritten32);
-        RtlFreeHeap(RtlGetProcessHeap(), 0, LocalBuffer);
+
+        if (LocalBuffer != StaticBuffer)
+            RtlFreeHeap(RtlGetProcessHeap(), 0, LocalBuffer);
     }
 
     /* Return the error code */
@@ -797,9 +835,7 @@
     PDOS_FILE_DESCRIPTOR Descriptor = DosGetHandleFileDescriptor(FileHandle);
 
     DPRINT("DosSeekFile: FileHandle 0x%04X, Offset 0x%08X, Origin 0x%02X\n",
-           FileHandle,
-           Offset,
-           Origin);
+           FileHandle, Offset, Origin);
 
     if (Descriptor == NULL)
     {
@@ -950,11 +986,10 @@
         {
             // TODO: NOT IMPLEMENTED
             UNIMPLEMENTED;
-
             return FALSE;
         }
 
-        /* Read From Device I/O Control Channel */
+        /* Read from Device I/O Control Channel */
         case 0x02:
         {
             if (Node == NULL || !(Node->DeviceAttributes & DOS_DEVATTR_IOCTL))
@@ -974,7 +1009,7 @@
             return TRUE;
         }
 
-        /* Write To Device I/O Control Channel */
+        /* Write to Device I/O Control Channel */
         case 0x03:
         {
             if (Node == NULL || !(Node->DeviceAttributes & DOS_DEVATTR_IOCTL))
@@ -1071,5 +1106,4 @@
     }
 }
 
-
 /* EOF */