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Some of Arkady's fattab optimizations -- the others only increase the kernel 

size for Watcom.


git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@898 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Bart Oldeman 2004-04-24 15:53:21 +00:00
parent 3227b87d5d
commit 490a27b857
1 changed files with 7 additions and 8 deletions
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15
kernel/fattab.c
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@ -145,9 +145,9 @@ void write_fsinfo(struct dpb FAR * dpbp)
/* */
/* 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 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
/* 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 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
/* 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))