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Diffstat (limited to 'src/fake86/disk.c')
| -rwxr-xr-x | src/fake86/disk.c | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/src/fake86/disk.c b/src/fake86/disk.c new file mode 100755 index 0000000..b09c8e2 --- /dev/null +++ b/src/fake86/disk.c @@ -0,0 +1,182 @@ +/* + 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]; +} |