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Support for non-standard GBS files with a loading address at 0

This commit is contained in:
Lior Halphon 2021-04-19 20:58:27 +03:00
parent c29edc1963
commit a2d3b8c174
1 changed files with 51 additions and 30 deletions
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79
Core/gb.c
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@ -303,6 +303,26 @@ int GB_load_rom(GB_gameboy_t *gb, const char *path)
}
#define GBS_ENTRY 0x61
#define GBS_ENTRY_SIZE 13
static void generate_gbs_entry(GB_gameboy_t *gb, uint8_t *data)
{
memcpy(data, (uint8_t[]) {
0xCD, // Call $XXXX
LE16(gb->gbs_header.init_address),
LE16(gb->gbs_header.init_address) >> 8,
0x76, // HALT
0x00, // NOP
0xAF, // XOR a
0xE0, // LDH [$FFXX], a
GB_IO_IF,
0xCD, // Call $XXXX
LE16(gb->gbs_header.play_address),
LE16(gb->gbs_header.play_address) >> 8,
0x18, // JR pc ± $XX
-10 // To HALT
}, GBS_ENTRY_SIZE);
}
void GB_gbs_switch_track(GB_gameboy_t *gb, uint8_t track)
{
@ -325,8 +345,19 @@ void GB_gbs_switch_track(GB_gameboy_t *gb, uint8_t track)
if (gb->gbs_header.TAC & 0x80) {
gb->cgb_double_speed = true; // Might mean double speed mode on a DMG
}
gb->sp = LE16(gb->gbs_header.sp);
gb->pc = GBS_ENTRY;
if (gb->gbs_header.load_address) {
gb->sp = LE16(gb->gbs_header.sp);
gb->pc = GBS_ENTRY;
}
else {
gb->pc = gb->sp = LE16(gb->gbs_header.sp - GBS_ENTRY_SIZE);
uint8_t entry[GBS_ENTRY_SIZE];
generate_gbs_entry(gb, entry);
for (unsigned i = 0; i < sizeof(entry); i++) {
GB_write_memory(gb, gb->pc + i, entry[i]);
}
}
gb->boot_rom_finished = true;
gb->a = track;
if (gb->sgb) {
@ -347,9 +378,10 @@ int GB_load_gbs(GB_gameboy_t *gb, const char *path, GB_gbs_info_t *info)
}
fread(&gb->gbs_header, sizeof(gb->gbs_header), 1, f);
if (gb->gbs_header.magic != BE32('GBS\x01') ||
LE16(gb->gbs_header.load_address) < 0x6e ||
LE16(gb->gbs_header.load_address) >= 0x8000) {
GB_log(gb, "Not a valid GBS file: %s.\n", strerror(errno));
((LE16(gb->gbs_header.load_address) < GBS_ENTRY + GBS_ENTRY_SIZE ||
LE16(gb->gbs_header.load_address) >= 0x8000) &&
LE16(gb->gbs_header.load_address) != 0)) {
GB_log(gb, "Not a valid GBS file.\n");
fclose(f);
return -1;
}
@ -389,32 +421,21 @@ int GB_load_gbs(GB_gameboy_t *gb, const char *path, GB_gbs_info_t *info)
bool has_interrupts = gb->gbs_header.TAC & 0x40;
// Generate interrupt handlers
for (unsigned i = 0; i <= (has_interrupts? 0x50 : 0x38); i += 8) {
gb->rom[i] = 0xc3; // jp $XXXX
gb->rom[i + 1] = (LE16(gb->gbs_header.load_address) + i);
gb->rom[i + 2] = (LE16(gb->gbs_header.load_address) + i) >> 8;
}
for (unsigned i = has_interrupts? 0x58 : 0x40; i <= 0x60; i += 8) {
gb->rom[i] = 0xc9; // ret
if (gb->gbs_header.load_address) {
// Generate interrupt handlers
for (unsigned i = 0; i <= (has_interrupts? 0x50 : 0x38); i += 8) {
gb->rom[i] = 0xc3; // jp $XXXX
gb->rom[i + 1] = (LE16(gb->gbs_header.load_address) + i);
gb->rom[i + 2] = (LE16(gb->gbs_header.load_address) + i) >> 8;
}
for (unsigned i = has_interrupts? 0x58 : 0x40; i <= 0x60; i += 8) {
gb->rom[i] = 0xc9; // ret
}
// Generate entry
generate_gbs_entry(gb, gb->rom + GBS_ENTRY);
}
// Generate entry
memcpy(gb->rom + GBS_ENTRY, (uint8_t[]) {
0xCD, // Call $XXXX
LE16(gb->gbs_header.init_address),
LE16(gb->gbs_header.init_address) >> 8,
0x76, // HALT
0x00, // NOP
0xAF, // XOR a
0xE0, // LDH [$FFXX], a
GB_IO_IF,
0xCD, // Call $XXXX
LE16(gb->gbs_header.play_address),
LE16(gb->gbs_header.play_address) >> 8,
0x18, // JR pc ± $XX
-10 // To HALT
}, 13);
GB_gbs_switch_track(gb, gb->gbs_header.first_track - 1);
if (info) {