dos33fsprogs/utils/dos33fs-utils/dos33_vtoc_bitmap.c
Vince Weaver 6b5c3612b0 dos33: fix disk corruption on DELETE
was using &vtoc where it should have just been vtoc so writing the
pointer value rather than the buffer.  urgh
2021-08-24 18:15:00 -04:00

212 lines
4.6 KiB
C

#include <stdio.h>
#include "dos33.h"
/* FIXME: this code assumes that we have 16 sectors pretty much everywhere */
static int ones_lookup[16]={
/* 0x0 = 0000 */ 0,
/* 0x1 = 0001 */ 1,
/* 0x2 = 0010 */ 1,
/* 0x3 = 0011 */ 2,
/* 0x4 = 0100 */ 1,
/* 0x5 = 0101 */ 2,
/* 0x6 = 0110 */ 2,
/* 0x7 = 0111 */ 3,
/* 0x8 = 1000 */ 1,
/* 0x9 = 1001 */ 2,
/* 0xA = 1010 */ 2,
/* 0xB = 1011 */ 3,
/* 0xC = 1100 */ 2,
/* 0xD = 1101 */ 3,
/* 0xE = 1110 */ 3,
/* 0xF = 1111 */ 4,
};
/* could be replaced by "find leading 1" instruction */
/* if available */
static int find_first_one(unsigned char byte) {
int i=0;
if (byte==0) return -1;
while((byte & (0x1<<i))==0) {
i++;
}
return i;
}
/* Return how many bytes free in the filesystem */
/* by reading the VTOC_FREE_BITMAP */
int dos33_vtoc_free_space(unsigned char *vtoc) {
unsigned char bitmap[4];
int i,sectors_free=0;
for(i=0;i<TRACKS_PER_DISK;i++) {
bitmap[0]=vtoc[VTOC_FREE_BITMAPS+(i*4)];
bitmap[1]=vtoc[VTOC_FREE_BITMAPS+(i*4)+1];
sectors_free+=ones_lookup[bitmap[0]&0xf];
sectors_free+=ones_lookup[(bitmap[0]>>4)&0xf];
sectors_free+=ones_lookup[bitmap[1]&0xf];
sectors_free+=ones_lookup[(bitmap[1]>>4)&0xf];
}
return sectors_free*BYTES_PER_SECTOR;
}
/* free a sector from the sector bitmap */
void dos33_vtoc_free_sector(unsigned char *vtoc, int track, int sector) {
if (debug) {
fprintf(stderr,"vtoc_free: freeing T=%d S=%d\n",
track,sector);
}
/* each bitmap is 32 bits. With 16-sector tracks only first 16 used */
/* 1 indicates free, 0 indicates used */
if (sector<8) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+1]|=(0x1<<sector);
}
else if (sector<16) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+0]|=(0x1<<(sector-8));
}
else if (sector<24) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+3]|=(0x1<<(sector-16));
}
else if (sector<32) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+2]|=(0x1<<(sector-24));
}
else {
fprintf(stderr,"Error vtoc_free_sector! sector too big %d\n",sector);
}
}
/* reserve a sector in the sector bitmap */
void dos33_vtoc_reserve_sector(unsigned char *vtoc, int track, int sector) {
/* each bitmap is 32 bits. With 16-sector tracks only first 16 used */
/* 1 indicates free, 0 indicates used */
if (sector<8) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+1]&=~(0x1<<sector);
}
else if (sector<16) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+0]&=~(0x1<<(sector-8));
}
else if (sector<24) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+3]&=~(0x1<<(sector-16));
}
else if (sector<32) {
vtoc[VTOC_FREE_BITMAPS+(track*4)+2]&=~(0x1<<(sector-24));
}
else {
fprintf(stderr,"Error vtoc_reserve_sector! sector too big %d\n",sector);
}
}
void dos33_vtoc_dump_bitmap(unsigned char *vtoc, int num_tracks) {
int i,j;
printf("\nFree sector bitmap:\n");
printf("\tU=used, .=free\n");
printf("\tTrack FEDCBA98 76543210\n");
for(i=0;i<num_tracks;i++) {
printf("\t $%02X: ",i);
for(j=0;j<8;j++) {
if ((vtoc[VTOC_FREE_BITMAPS+(i*4)]<<j)&0x80) {
printf(".");
}
else {
printf("U");
}
}
printf(" ");
for(j=0;j<8;j++) {
if ((vtoc[VTOC_FREE_BITMAPS+(i*4)+1]<<j)&0x80) {
printf(".");
}
else {
printf("U");
}
}
printf("\n");
}
}
/* reserve a sector in the sector bitmap */
int dos33_vtoc_find_free_sector(unsigned char *vtoc,
int *found_track, int *found_sector) {
int start_track,track_dir,i;
int bitmap;
int found=0;
/* Originally used to keep things near center of disk for speed */
/* We can use to avoid fragmentation possibly */
start_track=vtoc[VTOC_LAST_ALLOC_T]%TRACKS_PER_DISK;
track_dir=vtoc[VTOC_ALLOC_DIRECT];
if (track_dir==255) track_dir=-1;
if ((track_dir!=1) && (track_dir!=-1)) {
fprintf(stderr,"ERROR! Invalid track dir %i\n",track_dir);
}
if (((start_track>VTOC_TRACK) && (track_dir!=1)) ||
((start_track<VTOC_TRACK) && (track_dir!=-1))) {
fprintf(stderr,"Warning! Non-optimal values for track dir t=%i d=%i\n",
start_track,track_dir);
}
i=start_track;
do {
/* i+1 = sector 0..7 */
bitmap=vtoc[VTOC_FREE_BITMAPS+(i*4)+1];
if (bitmap!=0x00) {
*found_sector=find_first_one(bitmap);
*found_track=i;
found++;
break;
}
/* i+0 = sector 8..15 */
bitmap=vtoc[VTOC_FREE_BITMAPS+(i*4)];
if (bitmap!=0x00) {
*found_sector=find_first_one(bitmap)+8;
*found_track=i;
found++;
break;
}
/* Move to next track, handling overflows */
i+=track_dir;
if (i<0) {
i=VTOC_TRACK;
track_dir=1;
}
if (i>=TRACKS_PER_DISK) {
i=VTOC_TRACK;
track_dir=-1;
}
} while (i!=start_track);
if (found) {
/* clear bit indicating in use */
dos33_vtoc_reserve_sector(vtoc, *found_track, *found_sector);
return 0;
}
/* no room */
return -1;
}