[Freedos-cvs] kernel/kernel fattab.c,1.21,1.22

[Bart O. <bar...@us...>]

Update of /cvsroot/freedos/kernel/kernel
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv27587

Modified Files:
	fattab.c 
Log Message:
Some of Arkady's fattab optimizations -- the others only increase the kernel
size for Watcom.


Index: fattab.c
===================================================================
RCS file: /cvsroot/freedos/kernel/kernel/fattab.c,v
retrieving revision 1.21
retrieving revision 1.22
diff -u -d -r1.21 -r1.22
--- fattab.c	7 Feb 2004 18:04:49 -0000	1.21
+++ fattab.c	24 Apr 2004 15:53:21 -0000	1.22
@@ -145,9 +145,9 @@
 /*                                                              */
 /* The FAT file system is difficult to trace through FAT table. */
 /* There are two kinds of FAT's, 12 bit and 16 bit. The 16 bit  */
-/* FAT is the easiest, since it is noting more than a series of */
-/* UWORD's. The 12 bit FAT is difficult, because it packs 3 FAT */
-/* entries into two BYTE's. The are packed as follows:          */
+/* FAT is the easiest, since it is nothing more than a series   */
+/* of UWORD's. The 12 bit FAT is difficult, because it packs 3  */
+/* FAT entries into two BYTE's. These are packed as follows:    */
 /*                                                              */
 /*      0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009 ...    */
 /*                                                              */
@@ -177,9 +177,8 @@
 
     /* form an index so that we can read the block as a     */
     /* byte array                                           */
-    idx = (unsigned) ((((unsigned)Cluster1 << 1) + (unsigned)Cluster1) >> 1)
-      % dpbp->dpb_secsize;
-    
+    idx = (((unsigned)Cluster1 << 1) + (unsigned)Cluster1) % dpbp->dpb_secsize;
+
     /* Test to see if the cluster straddles the block. If   */
     /* it does, get the next block and use both to form the */
     /* the FAT word. Otherwise, just point to the next      */
@@ -201,13 +200,13 @@
     /* Now pack the value in                                */
     if ((unsigned)Cluster1 & 0x01)
     {
-      *fbp0 = (*fbp0 & 0x0f) | (((UBYTE)Cluster2 & 0x0f) << 4);
+      *fbp0 = (*fbp0 & 0x0f) | (UBYTE)((UBYTE)Cluster2 << 4);
       *fbp1 = (UBYTE)((unsigned)Cluster2 >> 4);
     }
     else
     {
       *fbp0 = (UBYTE)Cluster2;
-      *fbp1 = (*fbp1 & 0xf0) | ((UBYTE)((unsigned)Cluster2 >> 8) & 0x0f);
+      *fbp1 = (*fbp1 & 0xf0) | (UBYTE)((unsigned)Cluster2 >> 8);
     }
   }
   else if (ISFAT16(dpbp))