f6716cd74b
sector"(FAT16), or "dwords per sector"(FAT32) value instead of multiplying it first. For FAT12 the *3/2 works out a little differently: here we first multiply by 3 and then divide by the number of "nibbles per sector". git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@904 6ac86273-5f31-0410-b378-82cca8765d1b
380 lines
12 KiB
C
380 lines
12 KiB
C
/****************************************************************/
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/* */
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/* fattab.c */
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/* */
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/* FAT File System Table Functions */
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/* */
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/* Copyright (c) 1995 */
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/* Pasquale J. Villani */
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/* All Rights Reserved */
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/* */
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/* This file is part of DOS-C. */
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/* */
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/* DOS-C is free software; you can redistribute it and/or */
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/* modify it under the terms of the GNU General Public License */
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/* as published by the Free Software Foundation; either version */
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/* 2, or (at your option) any later version. */
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/* */
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/* DOS-C is distributed in the hope that it will be useful, but */
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/* WITHOUT ANY WARRANTY; without even the implied warranty of */
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/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See */
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/* the GNU General Public License for more details. */
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/* */
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/* You should have received a copy of the GNU General Public */
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/* License along with DOS-C; see the file COPYING. If not, */
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/* write to the Free Software Foundation, 675 Mass Ave, */
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/* Cambridge, MA 02139, USA. */
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/****************************************************************/
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#include "portab.h"
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#include "globals.h"
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#ifdef VERSION_STRINGS
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static BYTE *RcsId =
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"$Id$";
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#endif
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/************************************************************************/
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/* */
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/* cluster/sector routines */
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/* */
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/************************************************************************/
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#ifndef ISFAT32
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int ISFAT32(struct dpb FAR * dpbp)
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{
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return _ISFAT32(dpbp);
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}
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#endif
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struct buffer FAR *getFATblock(CLUSTER clussec, struct dpb FAR * dpbp)
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{
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unsigned secdiv;
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struct buffer FAR *bp;
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CLUSTER max_cluster = dpbp->dpb_size;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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max_cluster = dpbp->dpb_xsize;
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#endif
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if (clussec <= 1 || clussec > max_cluster)
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{
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put_string("run CHKDSK: trying to access invalid cluster 0x");
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#ifdef WITHFAT32
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put_unsigned((unsigned)(clussec >> 16), 16, 4);
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#endif
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put_unsigned((unsigned)(clussec & 0xffffu), 16, 4);
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put_console('\n');
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return NULL;
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}
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secdiv = dpbp->dpb_secsize;
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if (ISFAT12(dpbp))
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{
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clussec = (unsigned)clussec * 3;
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secdiv *= 2;
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}
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else /* FAT16 or FAT32 */
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{
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secdiv /= 2;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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secdiv /= 2;
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#endif
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}
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clussec /= secdiv;
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clussec += dpbp->dpb_fatstrt;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp) && (dpbp->dpb_xflags & FAT_NO_MIRRORING))
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{
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/* we must modify the active fat,
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it's number is in the 0-3 bits of dpb_xflags */
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clussec += (dpbp->dpb_xflags & 0xf) * dpbp->dpb_xfatsize;
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}
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#endif
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bp = getblock(clussec, dpbp->dpb_unit);
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if (bp)
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{
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bp->b_flag &= ~(BFR_DATA | BFR_DIR);
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bp->b_flag |= BFR_FAT | BFR_VALID;
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bp->b_dpbp = dpbp;
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bp->b_copies = dpbp->dpb_fats;
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bp->b_offset = dpbp->dpb_fatsize;
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#ifdef WITHFAT32
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if (ISFAT32(dpbp))
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{
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if (dpbp->dpb_xflags & FAT_NO_MIRRORING)
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bp->b_copies = 1;
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}
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#endif
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}
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return bp;
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}
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#ifdef WITHFAT32
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void read_fsinfo(struct dpb FAR * dpbp)
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{
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struct buffer FAR *bp;
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struct fsinfo FAR *fip;
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bp = getblock(dpbp->dpb_xfsinfosec, dpbp->dpb_unit);
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bp->b_flag &= ~(BFR_DATA | BFR_DIR | BFR_FAT | BFR_DIRTY);
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bp->b_flag |= BFR_VALID;
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fip = (struct fsinfo FAR *)&bp->b_buffer[0x1e4];
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dpbp->dpb_xnfreeclst = fip->fi_nfreeclst;
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dpbp->dpb_xcluster = fip->fi_cluster;
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}
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void write_fsinfo(struct dpb FAR * dpbp)
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{
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struct buffer FAR *bp;
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struct fsinfo FAR *fip;
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bp = getblock(dpbp->dpb_xfsinfosec, dpbp->dpb_unit);
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bp->b_flag &= ~(BFR_DATA | BFR_DIR | BFR_FAT);
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bp->b_flag |= BFR_VALID | BFR_DIRTY;
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fip = (struct fsinfo FAR *)&bp->b_buffer[0x1e4];
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fip->fi_nfreeclst = dpbp->dpb_xnfreeclst;
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fip->fi_cluster = dpbp->dpb_xcluster;
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}
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#endif
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/* */
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/* The FAT file system is difficult to trace through FAT table. */
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/* There are two kinds of FAT's, 12 bit and 16 bit. The 16 bit */
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/* FAT is the easiest, since it is nothing more than a series */
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/* of UWORD's. The 12 bit FAT is difficult, because it packs 3 */
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/* FAT entries into two BYTE's. These are packed as follows: */
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/* */
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/* 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009 ... */
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/* */
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/* are packed as */
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/* */
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/* 0x03 0x40 0x00 0x05 0x60 0x00 0x07 0x80 0x00 0x09 ... */
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/* */
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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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{
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struct buffer FAR *bp;
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/* Get the block that this cluster is in */
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bp = getFATblock(Cluster1, dpbp);
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if (bp == NULL)
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return DE_BLKINVLD;
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if (ISFAT12(dpbp))
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{
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unsigned idx;
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REG UBYTE FAR *fbp0, FAR * fbp1;
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struct buffer FAR * bp1;
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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 = (((unsigned)Cluster1 >> 1) + (unsigned)Cluster1) % dpbp->dpb_secsize;
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/* Test to see if the cluster straddles the block. If */
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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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fbp0 = &bp->b_buffer[idx];
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fbp1 = fbp0 + 1;
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if (idx >= (unsigned)dpbp->dpb_secsize - 1)
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{
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bp1 = getFATblock((unsigned)Cluster1 + 1, dpbp);
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if (bp1 == 0)
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return DE_BLKINVLD;
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bp1->b_flag |= BFR_DIRTY | BFR_VALID;
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fbp1 = &bp1->b_buffer[0];
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}
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/* Now pack the value in */
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if ((unsigned)Cluster1 & 0x01)
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{
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*fbp0 = (*fbp0 & 0x0f) | (UBYTE)((UBYTE)Cluster2 << 4);
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*fbp1 = (UBYTE)((unsigned)Cluster2 >> 4);
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}
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else
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{
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*fbp0 = (UBYTE)Cluster2;
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/* Cluster2 may be set to LONG_LAST_CLUSTER == 0x0FFFFFFFUL or 0xFFFF */
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/* -- please don't optimize to (UBYTE)((unsigned)Cluster2 >> 8)! */
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*fbp1 = (*fbp1 & 0xf0) | ((UBYTE)((unsigned)Cluster2 >> 8) & 0x0f);
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}
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}
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else if (ISFAT16(dpbp))
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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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/* Finally, put the word into the buffer and mark the */
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/* buffer as dirty. */
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fputword(
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&bp->b_buffer[((unsigned)Cluster1 * SIZEOF_CLST16) % dpbp->dpb_secsize],
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(UWORD)Cluster2);
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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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/* form an index so that we can read the block as a */
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/* byte array */
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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(
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&bp->b_buffer[(UWORD) ((Cluster1 * SIZEOF_CLST32) % dpbp->dpb_secsize)],
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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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/* update the free space count */
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bp->b_flag |= BFR_DIRTY | BFR_VALID;
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if (Cluster2 == FREE)
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{
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#ifdef WITHFAT32
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if (ISFAT32(dpbp) && dpbp->dpb_xnfreeclst != XUNKNCLSTFREE)
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{
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/* update the free space count for returned */
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/* cluster */
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++dpbp->dpb_xnfreeclst;
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write_fsinfo(dpbp);
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}
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else
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#endif
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if (dpbp->dpb_nfreeclst != UNKNCLSTFREE)
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++dpbp->dpb_nfreeclst;
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}
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/*if (Cluster2 == FREE)
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{ */
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/* update the free space count for returned */
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/* cluster */
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/* ++dpbp->dpb_nfreeclst;
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} */
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/* update the free space count for removed */
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/* cluster */
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/* BUG: was counted twice for 2nd,.. cluster. moved to find_fat_free() */
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/* BO: don't completely understand this yet - leave here for now as
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a comment */
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/* else
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{
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--dpbp->dpb_nfreeclst;
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} */
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return SUCCESS;
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}
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/* Given the disk parameters, and a cluster number, this function
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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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/* Get the block that this cluster is in */
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bp = getFATblock(ClusterNum, dpbp);
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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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unsigned idx;
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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 = (((unsigned)ClusterNum >> 1) + (unsigned)ClusterNum) %
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dpbp->dpb_secsize;
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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);
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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[((unsigned)ClusterNum * SIZEOF_CLST16) %
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dpbp->dpb_secsize]);
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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[((unsigned)ClusterNum * SIZEOF_CLST32) %
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dpbp->dpb_secsize]);
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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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}
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