kolibrios/programs/emulator/dgen-sdl-1.33/romload.c
turbocat ea1a60faa3 Upload DGEN port source
git-svn-id: svn://kolibrios.org@9837 a494cfbc-eb01-0410-851d-a64ba20cac60
2022-06-15 18:25:17 +00:00

132 lines
3.0 KiB
C

/*
DGen/SDL v1.27+
Module for loading in the different ROM image types (.bin/.smd)
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include "romload.h"
#include "system.h"
static const char *rom_path = "roms";
void set_rom_path(const char *path)
{
rom_path = path;
}
/*
WHAT YOU FIND IN THE 512 BYTES HEADER:
0: Number of blocks 1
1: H03 *
2: SPLIT? 2
8: HAA *
9: HBB *
ALL OTHER BYTES: H00
1: This first byte should have the number of 16KB blocks the rom has.
The header isn't part of the formula, so this number is:
[size of rom-512]/16384
If the size is more than 255, the value should be H00.
2: This byte indicates if the ROM is a part of a splitted rom series. If
the rom is the last part of the series (or isn't a splitted rom at all),
this byte should be H00. In other cases should be H40. See "CREATING
SPLITTED ROMS" for details on this format.
*/
/*
Allocate a buffer and stuff the named ROM inside. If rom_size is non-NULL,
store the ROM size there.
*/
uint8_t *load_rom(size_t *rom_size, const char *name)
{
FILE *file;
size_t size;
uint8_t *rom;
int error;
void *context = NULL;
if (name == NULL)
return NULL;
file = dgen_fopen(rom_path, name, (DGEN_READ | DGEN_CURRENT));
if (file == NULL) {
fprintf(stderr, "%s: can't open ROM file.\n", name);
return NULL;
}
retry:
/* A valid ROM will surely not be bigger than 64MB. */
rom = load(&context, &size, file, (64 * 1024 * 1024));
error = errno;
if (rom == NULL) {
if (error)
fprintf(stderr, "%s: unable to load ROM: %s.\n", name,
strerror(error));
else
fprintf(stderr, "%s: no valid ROM found.\n",
name);
load_finish(&context);
fclose(file);
return NULL;
}
if (size < 512) {
/* ROM file too small */
unload(rom);
goto retry;
}
/*
If "SEGA" isn't found at 0x100 and the total size minus 512 is a
multiple of 0x4000, it probably is a SMD.
*/
if (memcmp(&rom[0x100], "SEGA", 4)) {
uint8_t *dst = rom;
uint8_t *src = &rom[0x200];
size_t chunks = ((size - 0x200) / 0x4000);
if (((size - 0x200) & (0x4000 - 1)) != 0)
goto bad_rom;
size -= 0x200;
/* Corrupt ROM? Complain and continue anyway. */
if (((rom[0] != 0x00) && (rom[0] != chunks)) ||
(rom[8] != 0xaa) || (rom[9] != 0xbb))
fprintf(stderr, "%s: corrupt SMD header.\n", name);
/*
De-interleave ROM, overwrite SMD header with the result.
*/
while (chunks) {
size_t i;
uint8_t tmp[0x2000];
memcpy(tmp, src, 0x2000);
src += 0x2000;
for (i = 0; (i != 0x2000); ++i) {
*(dst++) = *(src++);
*(dst++) = tmp[i];
}
--chunks;
}
/* Does it look like a valid ROM now? */
if (memcmp(&rom[0x100], "SEGA", 4)) {
bad_rom:
/* Invalid ROM */
unload(rom);
goto retry;
}
}
load_finish(&context);
fclose(file);
if (rom_size != NULL)
*rom_size = size;
return rom;
}
void unload_rom(uint8_t *rom)
{
unload(rom);
}