mirror of https://github.com/FDOS/kernel.git
Merged next_cluster and link_fat into one function depending on a
special Cluster2 value. More optimizations later. git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@906 6ac86273-5f31-0410-b378-82cca8765d1b
This commit is contained in:
Bart Oldeman
parent
115b2bf68d
commit
bfe9252c2b
164
kernel/fattab.c
164
kernel/fattab.c
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@ -40,6 +40,10 @@ static BYTE *RcsId =
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/* */
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/************************************************************************/
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/* special "impossible" "Cluster2" value of 1 denotes reading the
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cluster number rather than overwriting it */
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#define READ_CLUSTER 1
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#ifndef ISFAT32
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int ISFAT32(struct dpb FAR * dpbp)
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{
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@ -166,8 +170,8 @@ void write_fsinfo(struct dpb FAR * dpbp)
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/* 12 bytes are compressed to 9 bytes */
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/* */
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unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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REG CLUSTER Cluster2)
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CLUSTER link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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REG CLUSTER Cluster2)
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{
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struct buffer FAR *bp;
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unsigned idx;
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@ -176,12 +180,16 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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bp = getFATblock(Cluster1, dpbp, &idx);
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if (bp == NULL)
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return DE_BLKINVLD;
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return 1; /* the only error code possible here */
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if (ISFAT12(dpbp))
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{
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REG UBYTE FAR *fbp0, FAR * fbp1;
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struct buffer FAR * bp1;
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union {
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UBYTE bytes[2];
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unsigned word;
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} clusterbuff;
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/* form an index so that we can read the block as a */
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/* byte array */
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@ -191,6 +199,10 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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/* it does, get the next block and use both to form the */
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/* the FAT word. Otherwise, just point to the next */
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/* block. */
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clusterbuff.bytes[0] = bp->b_buffer[idx];
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/* next byte, will be overwritten, if not valid */
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clusterbuff.bytes[1] = bp->b_buffer[idx + 1];
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fbp0 = &bp->b_buffer[idx];
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fbp1 = fbp0 + 1;
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@ -198,11 +210,39 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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{
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bp1 = getFATblock((unsigned)Cluster1 + 1, dpbp, NULL);
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if (bp1 == 0)
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return DE_BLKINVLD;
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return 1; /* the only error code possible here */
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bp1->b_flag |= BFR_DIRTY | BFR_VALID;
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if (Cluster2 != READ_CLUSTER)
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bp1->b_flag |= BFR_DIRTY | BFR_VALID;
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fbp1 = &bp1->b_buffer[0];
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clusterbuff.bytes[1] = bp1->b_buffer[0];
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}
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if (Cluster2 == READ_CLUSTER)
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{
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/* Now to unpack the contents of the FAT entry. Odd and */
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/* even bytes are packed differently. */
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#ifndef I86 /* the latter assumes byte ordering */
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if (Cluster1 & 0x01)
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idx =
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((clusterbuff.bytes[0] & 0xf0) >> 4) | (clusterbuff.bytes[1] << 4);
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else
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idx = clusterbuff.bytes[0] | ((clusterbuff.bytes[1] & 0x0f) << 8);
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#else
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if (Cluster1 & 0x01)
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idx = (unsigned short)clusterbuff.word >> 4;
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else
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idx = clusterbuff.word & 0x0fff;
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#endif
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if (idx >= MASK12)
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return LONG_LAST_CLUSTER;
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if (idx == BAD12)
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return LONG_BAD;
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return idx;
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}
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/* Now pack the value in */
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@ -223,6 +263,17 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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{
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/* form an index so that we can read the block as a */
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/* byte array */
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if (Cluster2 == READ_CLUSTER)
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{
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/* and get the cluster number */
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UWORD res = fgetword(&bp->b_buffer[idx * 2]);
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if (res >= MASK16)
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return LONG_LAST_CLUSTER;
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if (res == BAD16)
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return LONG_BAD;
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return res;
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}
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/* Finally, put the word into the buffer and mark the */
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/* buffer as dirty. */
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fputword(&bp->b_buffer[idx * 2], (UWORD)Cluster2);
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@ -232,13 +283,21 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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{
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/* form an index so that we can read the block as a */
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/* byte array */
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if (Cluster2 == READ_CLUSTER)
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{
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UDWORD res = fgetlong(&bp->b_buffer[idx * 4]);
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if (res > LONG_BAD)
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return LONG_LAST_CLUSTER;
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return res;
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}
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/* Finally, put the word into the buffer and mark the */
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/* buffer as dirty. */
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fputlong(&bp->b_buffer[idx * 4], Cluster2);
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}
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#endif
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else
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return DE_BLKINVLD;
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return 1;
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/* update the free space count */
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bp->b_flag |= BFR_DIRTY | BFR_VALID;
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@ -281,97 +340,6 @@ unsigned link_fat(struct dpb FAR * dpbp, CLUSTER Cluster1,
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looks at the FAT, and returns the next cluster in the clain. */
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CLUSTER next_cluster(struct dpb FAR * dpbp, CLUSTER ClusterNum)
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{
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struct buffer FAR *bp;
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unsigned idx;
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/* Get the block that this cluster is in */
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bp = getFATblock(ClusterNum, dpbp, &idx);
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if (bp == NULL)
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return 1; /* the only error code possible here */
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if (ISFAT12(dpbp))
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{
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union {
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UBYTE bytes[2];
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unsigned word;
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} clusterbuff;
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/* form an index so that we can read the block as a */
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/* byte array */
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idx /= 2;
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clusterbuff.bytes[0] = bp->b_buffer[idx];
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clusterbuff.bytes[1] = bp->b_buffer[idx + 1]; /* next byte, will be overwritten,
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if not valid */
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/* Test to see if the cluster straddles the block. If it */
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/* does, get the next block and use both to form the */
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/* the FAT word. Otherwise, just point to the next */
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/* block. */
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if (idx >= (unsigned)dpbp->dpb_secsize - 1)
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{
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bp = getFATblock(ClusterNum + 1, dpbp, NULL);
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if (bp == 0)
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return LONG_BAD;
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clusterbuff.bytes[1] = bp->b_buffer[0];
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}
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/* Now to unpack the contents of the FAT entry. Odd and */
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/* even bytes are packed differently. */
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#ifndef I86 /* the latter assumes byte ordering */
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if (ClusterNum & 0x01)
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idx =
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((clusterbuff.bytes[0] & 0xf0) >> 4) | (clusterbuff.bytes[1] << 4);
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else
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idx = clusterbuff.bytes[0] | ((clusterbuff.bytes[1] & 0x0f) << 8);
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#else
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if (ClusterNum & 0x01)
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idx = (unsigned short)clusterbuff.word >> 4;
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else
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idx = clusterbuff.word & 0x0fff;
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#endif
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if (idx >= MASK12)
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return LONG_LAST_CLUSTER;
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if (idx == BAD12)
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return LONG_BAD;
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return idx;
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}
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else if (ISFAT16(dpbp))
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{
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UWORD res;
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/* form an index so that we can read the block as a */
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/* byte array */
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/* and get the cluster number */
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res = fgetword(&bp->b_buffer[idx * 2]);
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if (res >= MASK16)
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return LONG_LAST_CLUSTER;
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if (res == BAD16)
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return LONG_BAD;
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return res;
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}
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#ifdef WITHFAT32
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else if (ISFAT32(dpbp))
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{
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UDWORD res;
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res = fgetlong(&bp->b_buffer[idx * 4]);
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if (res > LONG_BAD)
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return LONG_LAST_CLUSTER;
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return res;
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}
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#endif
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return LONG_LAST_CLUSTER;
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return link_fat(dpbp, ClusterNum, READ_CLUSTER);
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}
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