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FreeDOS/kernel/fattab.c
Jim Tabor 21bb3f6923 Fixed project history 
git-svn-id: https://svn.code.sf.net/p/freedos/svn/kernel/trunk@26 6ac86273-5f31-0410-b378-82cca8765d1b
2000-05-25 20:56:23 +00:00

386 lines
13 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 1.3 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 *, UCOUNT, UCOUNT);
UCOUNT link_fat16(struct dpb *, UCOUNT, UCOUNT);
UWORD next_cl12(struct dpb *, UCOUNT);
UWORD next_cl16(struct dpb *, UCOUNT);
#else
UCOUNT link_fat12();
UCOUNT link_fat16();
UWORD next_cl12();
UWORD next_cl16();
#endif
/************************************************************************/
/* */
/* cluster/sector routines */
/* */
/************************************************************************/
/* */
/* 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 *dpbp, UCOUNT Cluster1, REG UCOUNT Cluster2)
{
if (ISFAT12(dpbp))
return link_fat12(dpbp, Cluster1, Cluster2);
else if (ISFAT16(dpbp))
return link_fat16(dpbp, Cluster1, Cluster2);
else
return DE_BLKINVLD;
}
UCOUNT link_fat16(struct dpb * dpbp, UCOUNT Cluster1, UCOUNT Cluster2)
{
UCOUNT idx;
struct buffer FAR *bp;
UWORD Cl2 = Cluster2;
/* Get the block that this cluster is in */
bp = getblock((ULONG) (((ULONG) Cluster1) * SIZEOF_CLST16) / dpbp->dpb_secsize + dpbp->dpb_fatstrt,
dpbp->dpb_unit);
#ifdef DISPLAY_GETBLOCK
printf("FAT (link_fat16)\n");
#endif
if (bp == NULL)
return DE_BLKINVLD;
bp->b_flag &= ~(BFR_DATA | BFR_DIR);
bp->b_flag |= BFR_FAT;
bp->b_copies = dpbp->dpb_fats;
bp->b_offset_lo = dpbp->dpb_fatsize;
bp->b_offset_hi = dpbp->dpb_fatsize >> 8;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((LONG) Cluster1) * SIZEOF_CLST16) % dpbp->dpb_secsize;
/* Finally, put the word into the buffer and mark the */
/* buffer as dirty. */
fputword((WORD FAR *) & Cl2, (VOID FAR *) & (bp->b_buffer[idx]));
bp->b_flag |= BFR_DIRTY;
/* Return successful. */
/* update the free space count */
if (Cluster2 == FREE)
{
/* update the free space count for returned */
/* cluster */
if (dpbp->dpb_nfreeclst != UNKNCLUSTER)
++dpbp->dpb_nfreeclst;
}
else
{
/* update the free space count for removed */
/* cluster */
if (dpbp->dpb_nfreeclst != UNKNCLUSTER)
--dpbp->dpb_nfreeclst;
}
return SUCCESS;
}
UCOUNT link_fat12(struct dpb * 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 = getblock((ULONG) ((((Cluster1 << 1) + Cluster1) >> 1) / dpbp->dpb_secsize + dpbp->dpb_fatstrt),
dpbp->dpb_unit);
#ifdef DISPLAY_GETBLOCK
printf("FAT (link_fat12)\n");
#endif
if (bp == NULL)
return DE_BLKINVLD;
bp->b_flag &= ~(BFR_DATA | BFR_DIR);
bp->b_flag |= BFR_FAT;
bp->b_copies = dpbp->dpb_fats;
bp->b_offset_lo = dpbp->dpb_fatsize;
bp->b_offset_hi = dpbp->dpb_fatsize >> 8;
/* 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 = getblock((ULONG) (dpbp->dpb_fatstrt +
((((Cluster1 << 1) + Cluster1) >> 1) / dpbp->dpb_secsize))
+ 1,
dpbp->dpb_unit);
#ifdef DISPLAY_GETBLOCK
printf("FAT (link_fat12)\n");
#endif
if (bp1 == (struct buffer *)0)
return DE_BLKINVLD;
bp1->b_flag &= ~(BFR_DATA | BFR_DIR);
bp1->b_flag |= BFR_FAT | BFR_DIRTY;
bp1->b_copies = dpbp->dpb_fats;
bp1->b_offset_lo = dpbp->dpb_fatsize;
bp1->b_offset_hi = dpbp->dpb_fatsize >> 8;
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;
/* 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;
}
/* update the free space count */
if (Cluster2 == FREE)
{
/* update the free space count for returned */
/* cluster */
if (dpbp->dpb_nfreeclst != UNKNCLUSTER)
++dpbp->dpb_nfreeclst;
}
else
{
/* update the free space count for removed */
/* cluster */
if (dpbp->dpb_nfreeclst != UNKNCLUSTER)
--dpbp->dpb_nfreeclst;
}
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 * dpbp, REG 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 * dpbp, REG UCOUNT ClusterNum)
{
UCOUNT idx;
struct buffer FAR *bp;
UWORD RetCluster;
/* Get the block that this cluster is in */
bp = getblock((ULONG) (((ULONG) ClusterNum) * SIZEOF_CLST16) / dpbp->dpb_secsize + dpbp->dpb_fatstrt,
dpbp->dpb_unit);
#ifdef DISPLAY_GETBLOCK
printf("FAT (next_cl16)\n");
#endif
if (bp == NULL)
return DE_BLKINVLD;
bp->b_flag &= ~(BFR_DATA | BFR_DIR);
bp->b_flag |= BFR_FAT;
bp->b_copies = dpbp->dpb_fats;
bp->b_offset_lo = dpbp->dpb_fatsize;
bp->b_offset_hi = dpbp->dpb_fatsize >> 8;
/* form an index so that we can read the block as a */
/* byte array */
idx = (((LONG) 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;
}
UWORD next_cl12(struct dpb * 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 = getblock((ULONG) ((((ClusterNum << 1) + ClusterNum) >> 1) / dpbp->dpb_secsize + dpbp->dpb_fatstrt),
dpbp->dpb_unit);
#ifdef DISPLAY_GETBLOCK
printf("FAT (next_cl12)\n");
#endif
if (bp == NULL)
return LONG_BAD;
bp->b_flag &= ~(BFR_DATA | BFR_DIR);
bp->b_flag |= BFR_FAT;
bp->b_copies = dpbp->dpb_fats;
bp->b_offset_lo = dpbp->dpb_fatsize;
bp->b_offset_hi = dpbp->dpb_fatsize >> 8;
/* 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 = getblock((ULONG) (dpbp->dpb_fatstrt +
((((ClusterNum << 1) + ClusterNum) >> 1) / dpbp->dpb_secsize))
+ 1,
dpbp->dpb_unit);
#ifdef DISPLAY_GETBLOCK
printf("FAT (next_cl12)\n");
#endif
if (bp1 == (struct buffer *)0)
return LONG_BAD;
bp1->b_flag &= ~(BFR_DATA | BFR_DIR);
bp1->b_flag |= BFR_FAT;
bp1->b_copies = dpbp->dpb_fats;
bp1->b_offset_lo = dpbp->dpb_fatsize;
bp1->b_offset_hi = dpbp->dpb_fatsize >> 8;
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;
}
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