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Calculate the nibble/word/dword index of the FAT entry in the sector 

centrally in getFATblock.


git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@905 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Bart Oldeman 2004-04-29 12:48:18 +00:00
parent f6716cd74b
commit 115b2bf68d
1 changed files with 19 additions and 21 deletions
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40
kernel/fattab.c
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@ -47,7 +47,11 @@ int ISFAT32(struct dpb FAR * dpbp)
}
#endif
struct buffer FAR *getFATblock(CLUSTER clussec, struct dpb FAR * dpbp)
/* idx is a pointer to an index which is the nibble offset of the FAT
entry within the sector for FAT12, or word offset for FAT16, or
dword offset for FAT32 */
struct buffer FAR *getFATblock(CLUSTER clussec, struct dpb FAR * dpbp,
unsigned *idx)
{
unsigned secdiv;
struct buffer FAR *bp;
@ -83,6 +87,8 @@ struct buffer FAR *getFATblock(CLUSTER clussec, struct dpb FAR * dpbp)
secdiv /= 2;
#endif
}
if (idx)
*idx = (unsigned)(clussec % secdiv);
clussec /= secdiv;
clussec += dpbp->dpb_fatstrt;
#ifdef WITHFAT32
@ -164,22 +170,22 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
REG CLUSTER Cluster2)
{
struct buffer FAR *bp;
unsigned idx;
/* Get the block that this cluster is in */
bp = getFATblock(Cluster1, dpbp);
bp = getFATblock(Cluster1, dpbp, &idx);
if (bp == NULL)
return DE_BLKINVLD;
if (ISFAT12(dpbp))
{
unsigned idx;
REG UBYTE FAR *fbp0, FAR * fbp1;
struct buffer FAR * bp1;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((unsigned)Cluster1 >> 1) + (unsigned)Cluster1) % dpbp->dpb_secsize;
idx /= 2;
/* Test to see if the cluster straddles the block. If */
/* it does, get the next block and use both to form the */
@ -190,7 +196,7 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
if (idx >= (unsigned)dpbp->dpb_secsize - 1)
{
bp1 = getFATblock((unsigned)Cluster1 + 1, dpbp);
bp1 = getFATblock((unsigned)Cluster1 + 1, dpbp, NULL);
if (bp1 == 0)
return DE_BLKINVLD;
@ -219,9 +225,7 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
/* byte array */
/* Finally, put the word into the buffer and mark the */
/* buffer as dirty. */
fputword(
&bp->b_buffer[((unsigned)Cluster1 * SIZEOF_CLST16) % dpbp->dpb_secsize],
(UWORD)Cluster2);
fputword(&bp->b_buffer[idx * 2], (UWORD)Cluster2);
}
#ifdef WITHFAT32
else if (ISFAT32(dpbp))
@ -230,9 +234,7 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
/* byte array */
/* Finally, put the word into the buffer and mark the */
/* buffer as dirty. */
fputlong(
&bp->b_buffer[(UWORD) ((Cluster1 * SIZEOF_CLST32) % dpbp->dpb_secsize)],
Cluster2);
fputlong(&bp->b_buffer[idx * 4], Cluster2);
}
#endif
else
@ -280,9 +282,10 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
{
struct buffer FAR *bp;
unsigned idx;
/* Get the block that this cluster is in */
bp = getFATblock(ClusterNum, dpbp);
bp = getFATblock(ClusterNum, dpbp, &idx);
if (bp == NULL)
return 1; /* the only error code possible here */
@ -294,12 +297,9 @@ CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
unsigned word;
} clusterbuff;
unsigned idx;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((unsigned)ClusterNum >> 1) + (unsigned)ClusterNum) %
dpbp->dpb_secsize;
idx /= 2;
clusterbuff.bytes[0] = bp->b_buffer[idx];
@ -312,7 +312,7 @@ CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
/* block. */
if (idx >= (unsigned)dpbp->dpb_secsize - 1)
{
bp = getFATblock(ClusterNum + 1, dpbp);
bp = getFATblock(ClusterNum + 1, dpbp, NULL);
if (bp == 0)
return LONG_BAD;
@ -351,8 +351,7 @@ CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
/* byte array */
/* and get the cluster number */
res = fgetword(&bp->b_buffer[((unsigned)ClusterNum * SIZEOF_CLST16) %
dpbp->dpb_secsize]);
res = fgetword(&bp->b_buffer[idx * 2]);
if (res >= MASK16)
return LONG_LAST_CLUSTER;
@ -366,8 +365,7 @@ CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
{
UDWORD res;
res = fgetlong(&bp->b_buffer[((unsigned)ClusterNum * SIZEOF_CLST32) %
dpbp->dpb_secsize]);
res = fgetlong(&bp->b_buffer[idx * 4]);
if (res > LONG_BAD)
return LONG_LAST_CLUSTER;