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/*
Fake86: A portable, open-source 8086 PC emulator.
Copyright (C)2010-2013 Mike Chambers
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 2
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, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/* disk.c: disk emulation routines for Fake86. works at the BIOS interrupt 13h level. */
#include <stdint.h>
#include <stdio.h>
#include "disk.h"
#include "cpu.h"
extern uint8_t RAM[0x100000], cf, hdcount;
extern uint16_t segregs[4];
extern union _bytewordregs_ regs;
extern uint8_t read86 (uint32_t addr32);
extern void write86 (uint32_t addr32, uint8_t value);
struct struct_drive disk[256];
uint8_t sectorbuffer[512];
uint8_t insertdisk (uint8_t drivenum, char *filename) {
if (disk[drivenum].inserted) fclose (disk[drivenum].diskfile);
else disk[drivenum].inserted = 1;
disk[drivenum].diskfile = fopen (filename, "r+b");
if (disk[drivenum].diskfile==NULL) {
disk[drivenum].inserted = 0;
return (1);
}
fseek (disk[drivenum].diskfile, 0L, SEEK_END);
disk[drivenum].filesize = ftell (disk[drivenum].diskfile);
fseek (disk[drivenum].diskfile, 0L, SEEK_SET);
if (drivenum >= 0x80) { //it's a hard disk image
disk[drivenum].sects = 63;
disk[drivenum].heads = 16;
disk[drivenum].cyls = disk[drivenum].filesize / (disk[drivenum].sects * disk[drivenum].heads * 512);
hdcount++;
}
else { //it's a floppy image
disk[drivenum].cyls = 80;
disk[drivenum].sects = 18;
disk[drivenum].heads = 2;
if (disk[drivenum].filesize <= 1228800) disk[drivenum].sects = 15;
if (disk[drivenum].filesize <= 737280) disk[drivenum].sects = 9;
if (disk[drivenum].filesize <= 368640) {
disk[drivenum].cyls = 40;
disk[drivenum].sects = 9;
}
if (disk[drivenum].filesize <= 163840) {
disk[drivenum].cyls = 40;
disk[drivenum].sects = 8;
disk[drivenum].heads = 1;
}
}
return (0);
}
void ejectdisk (uint8_t drivenum) {
disk[drivenum].inserted = 0;
if (disk[drivenum].diskfile != NULL) fclose (disk[drivenum].diskfile);
}
void readdisk (uint8_t drivenum, uint16_t dstseg, uint16_t dstoff, uint16_t cyl, uint16_t sect, uint16_t head, uint16_t sectcount) {
uint32_t memdest, lba, fileoffset, cursect, sectoffset;
if (!sect || !disk[drivenum].inserted) return;
lba = ( (uint32_t) cyl * (uint32_t) disk[drivenum].heads + (uint32_t) head) * (uint32_t) disk[drivenum].sects + (uint32_t) sect - 1;
fileoffset = lba * 512;
if (fileoffset>disk[drivenum].filesize) return;
fseek (disk[drivenum].diskfile, fileoffset, SEEK_SET);
memdest = ( (uint32_t) dstseg << 4) + (uint32_t) dstoff;
//for the readdisk function, we need to use write86 instead of directly fread'ing into
//the RAM array, so that read-only flags are honored. otherwise, a program could load
//data from a disk over BIOS or other ROM code that it shouldn't be able to.
for (cursect=0; cursect<sectcount; cursect++) {
if (fread (sectorbuffer, 1, 512, disk[drivenum].diskfile) < 512) break;
for (sectoffset=0; sectoffset<512; sectoffset++) {
write86 (memdest++, sectorbuffer[sectoffset]);
}
}
regs.byteregs[regal] = cursect;
cf = 0;
regs.byteregs[regah] = 0;
}
void writedisk (uint8_t drivenum, uint16_t dstseg, uint16_t dstoff, uint16_t cyl, uint16_t sect, uint16_t head, uint16_t sectcount) {
uint32_t memdest, lba, fileoffset, cursect, sectoffset;
if (!sect || !disk[drivenum].inserted) return;
lba = ( (uint32_t) cyl * (uint32_t) disk[drivenum].heads + (uint32_t) head) * (uint32_t) disk[drivenum].sects + (uint32_t) sect - 1;
fileoffset = lba * 512;
if (fileoffset>disk[drivenum].filesize) return;
fseek (disk[drivenum].diskfile, fileoffset, SEEK_SET);
memdest = ( (uint32_t) dstseg << 4) + (uint32_t) dstoff;
for (cursect=0; cursect<sectcount; cursect++) {
for (sectoffset=0; sectoffset<512; sectoffset++) {
sectorbuffer[sectoffset] = read86 (memdest++);
}
fwrite (sectorbuffer, 1, 512, disk[drivenum].diskfile);
}
regs.byteregs[regal] = (uint8_t) sectcount;
cf = 0;
regs.byteregs[regah] = 0;
}
void diskhandler() {
static uint8_t lastdiskah[256], lastdiskcf[256];
switch (regs.byteregs[regah]) {
case 0: //reset disk system
regs.byteregs[regah] = 0;
cf = 0; //useless function in an emulator. say success and return.
break;
case 1: //return last status
regs.byteregs[regah] = lastdiskah[regs.byteregs[regdl]];
cf = lastdiskcf[regs.byteregs[regdl]];
return;
case 2: //read sector(s) into memory
if (disk[regs.byteregs[regdl]].inserted) {
readdisk (regs.byteregs[regdl], segregs[reges], getreg16 (regbx), regs.byteregs[regch] + (regs.byteregs[regcl]/64) *256, regs.byteregs[regcl] & 63, regs.byteregs[regdh], regs.byteregs[regal]);
cf = 0;
regs.byteregs[regah] = 0;
}
else {
cf = 1;
regs.byteregs[regah] = 1;
}
break;
case 3: //write sector(s) from memory
if (disk[regs.byteregs[regdl]].inserted) {
writedisk (regs.byteregs[regdl], segregs[reges], getreg16 (regbx), regs.byteregs[regch] + (regs.byteregs[regcl]/64) *256, regs.byteregs[regcl] & 63, regs.byteregs[regdh], regs.byteregs[regal]);
cf = 0;
regs.byteregs[regah] = 0;
}
else {
cf = 1;
regs.byteregs[regah] = 1;
}
break;
case 4:
case 5: //format track
cf = 0;
regs.byteregs[regah] = 0;
break;
case 8: //get drive parameters
if (disk[regs.byteregs[regdl]].inserted) {
cf = 0;
regs.byteregs[regah] = 0;
regs.byteregs[regch] = disk[regs.byteregs[regdl]].cyls - 1;
regs.byteregs[regcl] = disk[regs.byteregs[regdl]].sects & 63;
regs.byteregs[regcl] = regs.byteregs[regcl] + (disk[regs.byteregs[regdl]].cyls/256) *64;
regs.byteregs[regdh] = disk[regs.byteregs[regdl]].heads - 1;
if (regs.byteregs[regdl]<0x80) {
regs.byteregs[regbl] = 4; //else regs.byteregs[regbl] = 0;
regs.byteregs[regdl] = 2;
}
else regs.byteregs[regdl] = hdcount;
}
else {
cf = 1;
regs.byteregs[regah] = 0xAA;
}
break;
default:
cf = 1;
}
lastdiskah[regs.byteregs[regdl]] = regs.byteregs[regah];
lastdiskcf[regs.byteregs[regdl]] = cf;
if (regs.byteregs[regdl] & 0x80) RAM[0x474] = regs.byteregs[regah];
}
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