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/* Rainbow Image Utilities
* Copyright © 2008 Jeffrey Armstrong <jeff@rainbow-100.com>
* http://jeff.rainbow-100.com/
*
* This program 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 3 of the License, or
* (at your option) any later version.
*
* This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
*/
/* rbfloppy.obj - A collection of direct disk access routines
* by Jeff Armstrong
*/
#include <dos.h>
#include "rbfloppy.h"
#include <stdio.h>
/* Structure that represents the block of data needed to call interrupt
* 0x65, which allows direct disk access. The order here is very
* important.
*/
struct dsk_bios_block {
unsigned char command;
unsigned char drive_id;
unsigned char sector;
unsigned char phys_unit;
unsigned int track;
unsigned int sector_count;
unsigned int data;
unsigned int segment;
};
/* The map that is used to skew/deskew sector addresses */
static int skew[11] = {0,1,6,2,7,3,8,4,9,5,10};
/* The current program addressing mode */
static int current_mode = MODE_PHYSICAL;
/* An internal method to unskew a given sector number */
int unskew(int sector);
/* Writes a given sector using the data in buffer */
int write_sector(int unit, int track, int sector, char *buffer)
{
return access_sector(CMD_WRITE_VERIFY, unit, track, sector, buffer);
}
/* Reads a specified sector from disk into buffer */
int read_sector(int unit, int track, int sector, char *buffer)
{
return access_sector(CMD_READ, unit, track, sector, buffer);
}
/* Internal routine that performs all actual disk access through calls
* to interrupt 0x65. Some command ints are already #defined, but
* a few more exist that aren't listed here.
*/
int access_sector(int command, int unit, int track, int sector, char *buffer)
{
struct dsk_bios_block write;
struct SREGS segregs;
union REGS r;
char *pt;
/* Sectors are numbered 1 to 10 */
if(sector > 10)
return ERROR_BAD_SECTOR;
/* The current data segment is needed for the interrupt call */
segread(&segregs);
write.command = (unsigned char)command;
write.drive_id = (unsigned char)0xFF;
write.track = (unsigned int)track;
/* Determine the sector if skewing is necessary */
if(track > 1 && get_mode() == MODE_PHYSICAL)
write.sector = (unsigned char)unskew(sector);
else
write.sector = (unsigned char)sector;
write.sector_count = (unsigned int)1;
write.phys_unit = (unsigned char)(0+unit*16);
write.data = (unsigned int)buffer;
write.segment = segregs.ds;
/* Only for debugging */
pt = &write;
#ifdef DEBUG
printf("Sz: %d: 0:%d 1:%d 2:%d 3:%d 4:%d 5:%d 6:%d 7:%d of:%d ds%d\n",
sizeof(write),pt[0],pt[1],pt[2],pt[3],pt[4]+pt[5]*256,
pt[6]+pt[7]*256,pt[8]+pt[9]*256,pt[10]+pt[11]*256,
&buffer[0],segregs.ds);
#endif
r.x.bx = &write;
int86(FLOPPY_INTR,&r,&r);
if(r.h.al == 0)
return OK;
else
return ERROR_FROM_BIOS;
}
/* Determines the unit number for access_sector() from a given character.
* Expects a drive letter or a number. Returns -1 on error.
*/
int drive_id(char id)
{
int drv;
switch(id) {
case 'A':
case 'a':
case 0:
case '0':
drv = 0;
break;
case 'B':
case 'b':
case 1:
case '1':
drv = 1;
break;
case 'C':
case 'c':
case 2:
case '2':
drv = 2;
break;
case 'D':
case 'd':
case 3:
case '3':
drv = 3;
break;
default:
drv = -1;
}
return drv;
}
/* Returns an unskewed sector number from a skewed address */
int unskew(int sector) {
return sector <= 10 && sector > 0 ? skew[sector] : 1;
}
/* Sets the mode of the sector addressing to either physical or
* logical by assigning a static variable.
*/
void set_mode(int mode)
{
if(mode == MODE_PHYSICAL || mode == MODE_LOGICAL)
current_mode = mode;
}
/* Returns the current addressing mode */
int get_mode()
{
return current_mode;
}
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