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c1b1896480
FreeDOS/kernel/fattab.c
Bart Oldeman c1b1896480 LBA/FCB/FAT/SYS/Ctrl-C/ioctl fixes + memory savings 
git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@260 6ac86273-5f31-0410-b378-82cca8765d1b
2001-07-09 22:19:33 +00:00

451 lines
14 KiB
C
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/****************************************************************/
/* */
/* fattab.c */
/* */
/* FAT File System Table Functions */
/* */
/* Copyright (c) 1995 */
/* Pasquale J. Villani */
/* All Rights Reserved */
/* */
/* This file is part of DOS-C. */
/* */
/* DOS-C is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU General Public License */
/* as published by the Free Software Foundation; either version */
/* 2, or (at your option) any later version. */
/* */
/* DOS-C is distributed in the hope that it will be useful, but */
/* WITHOUT ANY WARRANTY; without even the implied warranty of */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See */
/* the GNU General Public License for more details. */
/* */
/* You should have received a copy of the GNU General Public */
/* License along with DOS-C; see the file COPYING. If not, */
/* write to the Free Software Foundation, 675 Mass Ave, */
/* Cambridge, MA 02139, USA. */
/****************************************************************/
#include "portab.h"
#include "globals.h"
#ifdef VERSION_STRINGS
static BYTE *RcsId = "$Id$";
#endif
/*
* $Log$
* Revision 1.7 2001/07/09 22:19:33 bartoldeman
* LBA/FCB/FAT/SYS/Ctrl-C/ioctl fixes + memory savings
*
* Revision 1.6 2001/06/03 14:16:17 bartoldeman
* BUFFERS tuning and misc bug fixes/cleanups (2024c).
*
* Revision 1.5 2001/04/21 22:32:53 bartoldeman
* Init DS=Init CS, fixed stack overflow problems and misc bugs.
*
* Revision 1.4 2001/04/15 03:21:50 bartoldeman
* See history.txt for the list of fixes.
*
* Revision 1.3 2000/05/25 20:56:21 jimtabor
* Fixed project history
*
* Revision 1.2 2000/05/08 04:30:00 jimtabor
* Update CVS to 2020
*
* Revision 1.1.1.1 2000/05/06 19:34:53 jhall1
* The FreeDOS Kernel. A DOS kernel that aims to be 100% compatible with
* MS-DOS. Distributed under the GNU GPL.
*
* Revision 1.6 1999/08/10 18:03:42 jprice
* ror4 2011-03 patch
*
* Revision 1.5 1999/05/03 06:25:45 jprice
* Patches from ror4 and many changed of signed to unsigned variables.
*
* Revision 1.4 1999/04/16 00:53:33 jprice
* Optimized FAT handling
*
* Revision 1.3 1999/04/11 04:33:38 jprice
* ror4 patches
*
* Revision 1.1.1.1 1999/03/29 15:42:09 jprice
* New version without IPL.SYS
*
* Revision 1.4 1999/02/09 02:54:23 jprice
* Added Pat's 1937 kernel patches
*
* Revision 1.3 1999/02/01 01:43:28 jprice
* Fixed findfirst function to find volume label with Windows long filenames
*
* Revision 1.2 1999/01/22 04:15:28 jprice
* Formating
*
* Revision 1.1.1.1 1999/01/20 05:51:00 jprice
* Imported sources
*
*
* Rev 1.7 09 Feb 1998 5:41:08 patv
* Eliminated FAT12 EOF and error returns.
*
* Rev 1.6 04 Jan 1998 23:14:38 patv
* Changed Log for strip utility
*
* Rev 1.5 16 Jan 1997 12:46:22 patv
* pre-Release 0.92 feature additions
*
* Rev 1.4 29 May 1996 21:15:14 patv
* bug fixes for v0.91a
*
* Rev 1.3 19 Feb 1996 3:20:08 patv
* Added NLS, int2f and config.sys processing
*
* Rev 1.2 01 Sep 1995 17:48:42 patv
* First GPL release.
*
* Rev 1.1 30 Jul 1995 20:50:26 patv
* Eliminated version strings in ipl
*
* Rev 1.0 02 Jul 1995 8:04:56 patv
* Initial revision.
*/
#ifdef PROTO
UCOUNT link_fat12(struct dpb FAR *, UCOUNT, UCOUNT);
UCOUNT link_fat16(struct dpb FAR *, UCOUNT, UCOUNT);
UWORD next_cl12(struct dpb FAR *, UCOUNT);
UWORD next_cl16(struct dpb FAR *, UCOUNT);
#else
UCOUNT link_fat12();
UCOUNT link_fat16();
UWORD next_cl12();
UWORD next_cl16();
#endif
/************************************************************************/
/* */
/* cluster/sector routines */
/* */
/************************************************************************/
struct buffer FAR *getFATblock(UWORD cluster, struct dpb FAR *dpbp)
{
ULONG sector;
struct buffer FAR *bp;
if (ISFAT12(dpbp))
{
sector = ((cluster << 1) + cluster) >> 1;
}
else /* FAT16 */
{
sector = (ULONG)cluster * SIZEOF_CLST16;
}
sector = sector / dpbp->dpb_secsize + dpbp->dpb_fatstrt;
bp = getblock(sector, dpbp->dpb_unit);
if (bp)
{
bp->b_flag &= ~(BFR_DATA | BFR_DIR);
bp->b_flag |= BFR_FAT | BFR_VALID;
bp->b_copies = dpbp->dpb_fats;
bp->b_offset_lo = dpbp->dpb_fatsize;
bp->b_offset_hi = dpbp->dpb_fatsize >> 8;
}
return bp;
}
/* */
/* 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: */
/* */
/* 0x0003 0x0004 0x0005 0x0006 0x0007 0x0008 0x0009 ... */
/* */
/* are packed as */
/* */
/* 0x03 0x40 0x00 0x05 0x60 0x00 0x07 0x80 0x00 0x09 ... */
/* */
/* 12 bytes are compressed to 9 bytes */
/* */
UCOUNT link_fat(struct dpb FAR *dpbp, UCOUNT Cluster1, REG UCOUNT Cluster2)
{
UCOUNT res;
if (ISFAT12(dpbp))
res = link_fat12(dpbp, Cluster1, Cluster2);
else if (ISFAT16(dpbp))
res = link_fat16(dpbp, Cluster1, Cluster2);
else
return DE_BLKINVLD;
/* update the free space count */
if (res == SUCCESS)
if (dpbp->dpb_nfreeclst != UNKNCLSTFREE)
{
if (Cluster2 == FREE)
{
/* update the free space count for returned */
/* cluster */
++dpbp->dpb_nfreeclst;
}
/* update the free space count for removed */
/* cluster */
/* BUG: was counted twice for 2nd,.. cluster. moved to find_fat_free() */
/* else {
--dpbp->dpb_nfreeclst;
}
*/
}
return res;
}
UCOUNT link_fat16(struct dpb FAR *dpbp, UCOUNT Cluster1, UCOUNT Cluster2)
{
UCOUNT idx;
struct buffer FAR *bp;
/* Get the block that this cluster is in */
bp = getFATblock( Cluster1, dpbp);
if (bp == NULL)
return DE_BLKINVLD;
/* form an index so that we can read the block as a */
/* byte array */
idx = (UWORD)(( Cluster1 * SIZEOF_CLST16) % dpbp->dpb_secsize);
/* Finally, put the word into the buffer and mark the */
/* buffer as dirty. */
fputword((WORD FAR *) & Cluster2, (VOID FAR *) & (bp->b_buffer[idx]));
bp->b_flag |= BFR_DIRTY | BFR_VALID;
/* Return successful. */
return SUCCESS;
}
UCOUNT link_fat12(struct dpb FAR *dpbp, UCOUNT Cluster1, UCOUNT Cluster2)
{
REG UBYTE FAR *fbp0,
FAR * fbp1;
UCOUNT idx;
struct buffer FAR *bp,
FAR * bp1;
/* Get the block that this cluster is in */
bp = getFATblock(Cluster1 , dpbp);
if (bp == NULL)
return DE_BLKINVLD;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((Cluster1 << 1) + Cluster1) >> 1) % 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 */
/* block. */
if (idx >= dpbp->dpb_secsize - 1)
{
bp1 = getFATblock(Cluster1 + 1,dpbp);
if (bp1 == 0)
return DE_BLKINVLD;
bp1->b_flag |= BFR_DIRTY | BFR_VALID;
fbp1 = (UBYTE FAR *) & (bp1->b_buffer[0]);
}
else
fbp1 = (UBYTE FAR *) & (bp->b_buffer[idx + 1]);
fbp0 = (UBYTE FAR *) & (bp->b_buffer[idx]);
bp->b_flag |= BFR_DIRTY | BFR_VALID;
/* Now pack the value in */
if (Cluster1 & 0x01)
{
*fbp0 = (*fbp0 & 0x0f) | ((Cluster2 & 0x0f) << 4);
*fbp1 = (Cluster2 >> 4) & 0xff;
}
else
{
*fbp0 = Cluster2 & 0xff;
*fbp1 = (*fbp1 & 0xf0) | ((Cluster2 >> 8) & 0x0f);
}
return SUCCESS;
}
/* Given the disk parameters, and a cluster number, this function
looks at the FAT, and returns the next cluster in the clain. */
UWORD next_cluster(struct dpb FAR *dpbp, UCOUNT ClusterNum)
{
if (ISFAT12(dpbp))
return next_cl12(dpbp, ClusterNum);
else if (ISFAT16(dpbp))
return next_cl16(dpbp, ClusterNum);
else
return LONG_LAST_CLUSTER;
}
UWORD next_cl16(struct dpb FAR *dpbp, UCOUNT ClusterNum)
{
struct buffer FAR *bp;
/* Get the block that this cluster is in */
bp = getFATblock( ClusterNum, dpbp);
if (bp == NULL)
return DE_BLKINVLD;
#ifndef I86
UCOUNT idx;
UWORD RetCluster;
/* form an index so that we can read the block as a */
/* byte array */
idx = (ClusterNum * SIZEOF_CLST16) % dpbp->dpb_secsize;
/* Get the cluster number, */
fgetword((VOID FAR *) & (bp->b_buffer[idx]), (WORD FAR *) & RetCluster);
/* and return successful. */
return RetCluster;
#else
/* this saves 2 WORDS of stack :-) */
return *(UWORD FAR *)&(bp->b_buffer[(ClusterNum * SIZEOF_CLST16) % dpbp->dpb_secsize]);
#endif
}
#if 0
/* old version - correct, but a bit complicated coded.
it's also on one of the critical stack path's
*/
UWORD next_cl12(struct dpb FAR *dpbp, REG UCOUNT ClusterNum)
{
REG UBYTE FAR *fbp0,
FAR * fbp1;
UCOUNT idx;
struct buffer FAR *bp,
FAR * bp1;
/* Get the block that this cluster is in */
bp = getFATblock(ClusterNum , dpbp);
if (bp == NULL)
return LONG_BAD;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((ClusterNum << 1) + ClusterNum) >> 1) % 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 */
/* block. */
if (idx >= dpbp->dpb_secsize - 1)
{
bp1 = getFATblock(ClusterNum +1, dpbp);
if (bp1 == 0)
return LONG_BAD;
fbp1 = (UBYTE FAR *) & (bp1->b_buffer[0]);
}
else
fbp1 = (UBYTE FAR *) & (bp->b_buffer[idx + 1]);
fbp0 = (UBYTE FAR *) & (bp->b_buffer[idx]);
/* Now to unpack the contents of the FAT entry. Odd and */
/* even bytes are packed differently. */
if (ClusterNum & 0x01)
ClusterNum = ((*fbp0 & 0xf0) >> 4) | (*fbp1 << 4);
else
ClusterNum = *fbp0 | ((*fbp1 & 0x0f) << 8);
if ((ClusterNum & MASK) == MASK)
ClusterNum = LONG_LAST_CLUSTER;
else if ((ClusterNum & BAD) == BAD)
ClusterNum = LONG_BAD;
return ClusterNum;
}
#else
/* new version - 50 byte smaller, saves 10 bytes on stack :-)
*/
UWORD next_cl12(struct dpb FAR *dpbp, REG UCOUNT ClusterNum)
{
union {
UBYTE bytes[2];
UCOUNT word;
} clusterbuff;
UCOUNT idx;
struct buffer FAR *bp;
/* Get the block that this cluster is in */
bp = getFATblock(ClusterNum , dpbp);
if (bp == NULL)
return LONG_BAD;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((ClusterNum << 1) + ClusterNum) >> 1) % dpbp->dpb_secsize;
clusterbuff.bytes[0] = bp->b_buffer[idx];
clusterbuff.bytes[1] = bp->b_buffer[idx+1]; /* next byte, will be overwritten,
if not valid */
/* 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 */
/* block. */
if (idx >= dpbp->dpb_secsize - 1)
{
bp = getFATblock(ClusterNum +1, dpbp);
if (bp == 0)
return LONG_BAD;
clusterbuff.bytes[1] = bp->b_buffer[0];
}
/* Now to unpack the contents of the FAT entry. Odd and */
/* even bytes are packed differently. */
#ifndef I86 /* the latter assumes byte ordering */
if (ClusterNum & 0x01)
ClusterNum = ((clusterbuff.byte[0] & 0xf0) >> 4) | (clusterbuff.byte[1] << 4);
else
ClusterNum = clusterbuff.byte[0] | ((clusterbuff.byte[0] & 0x0f) << 8);
#else
if (ClusterNum & 0x01)
ClusterNum = (unsigned short)clusterbuff.word >> 4;
else
ClusterNum = clusterbuff.word & 0x0fff;
#endif
if ((ClusterNum & MASK) == MASK)
ClusterNum = LONG_LAST_CLUSTER;
else if ((ClusterNum & BAD) == BAD)
ClusterNum = LONG_BAD;
return ClusterNum;
}
#endif
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