[pschweitzer] 71370: [VFATLIB] Update the amount of FAT entries taking into account that the first two are reserved and thus not usable. Patch by Wim Hueskes CORE-11283 #resolve #comment Committed ...

Author: pschweitzer
Date: Sun May 22 07:56:45 2016
New Revision: 71370

URL: http://svn.reactos.org/svn/reactos?rev=71370&view=rev
Log:
[VFATLIB]
Update the amount of FAT entries taking into account that the first two are reserved and
thus not usable.

Patch by Wim Hueskes

CORE-11283 #resolve #comment Committed in r71370, thanks for your patch!

Modified:
    trunk/reactos/sdk/lib/fslib/vfatlib/fat32.c

Modified: trunk/reactos/sdk/lib/fslib/vfatlib/fat32.c
URL:
http://svn.reactos.org/svn/reactos/trunk/reactos/sdk/lib/fslib/vfatlib/fat3…
==============================================================================
--- trunk/reactos/sdk/lib/fslib/vfatlib/fat32.c	[iso-8859-1] (original)
+++ trunk/reactos/sdk/lib/fslib/vfatlib/fat32.c	[iso-8859-1] Sun May 22 07:56:45 2016
@@ -397,6 +397,9 @@
     ULONG TmpVal1;
     ULONG TmpVal2;
     NTSTATUS Status;
+    ULONG UsableFatEntries;
+    ULONG FirstDataSector;
+    ULONG DataClusters;
 
     /* Calculate cluster size */
     if (ClusterSize == 0)
@@ -469,6 +472,20 @@
     BootSector.FATSectors32 = (TmpVal1 + (TmpVal2 - 1)) / TmpVal2;
     DPRINT("FATSectors32 = %lu\n", BootSector.FATSectors32);
 
+    /* edge case: first 2 fat entries are not usable, so the calculation might need a
correction */
+    UsableFatEntries = BootSector.FATSectors32 * (BootSector.BytesPerSector / 4) - 2;
+    FirstDataSector = BootSector.ReservedSectors + BootSector.FATCount *
BootSector.FATSectors32;
+    DataClusters = (BootSector.SectorsHuge - FirstDataSector) /
BootSector.SectorsPerCluster;
+    if (DataClusters > UsableFatEntries)
+    {
+        /* Need more fat entries */
+        BootSector.FATSectors32 += (DataClusters - UsableFatEntries);
+
+        DPRINT("UsableFatEntries = %lu\n", UsableFatEntries);
+        DPRINT("DataClusters = %lu\n", DataClusters);
+        DPRINT("BootSector.FATSectors32 incremented to %lu\n",
BootSector.FATSectors32);
+    }
+
     /* Init context data */
     Context->TotalSectorCount =
         2 + (BootSector.FATSectors32 * BootSector.FATCount) +
BootSector.SectorsPerCluster;