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#include "s98gen.h"
static uint32_t read32le(const void *dataptr, size_t offset) {
const uint8_t *data = (const uint8_t *)dataptr;
return ((uint32_t)data[offset+0]) | (((uint32_t)data[offset+1])<<8) |
(((uint32_t)data[offset+2])<<16) | (((uint32_t)data[offset+3])<<24);
}
bool s98gen_init(struct s98gen *s98, void *s98dataptr, size_t s98data_size) {
uint8_t *s98data = (uint8_t *)s98dataptr;
if (s98data_size < 0x20) {
// size of s98 header
return false;
}
if (s98data[0] != 'S' || s98data[1] != '9' ||
s98data[2] != '8') {
// file magic / version check
return false;
}
if ((s98data[3] != '1') && (s98data[3] != '3')) {
return false;
}
if (s98data[0xc] != 0) {
// COMPRESSING flag not zero
return false;
}
uint32_t clock = 7987200;
if ((s98data[3] == '3') && s98data[0x1c]) {
if (s98data_size < 0x30) {
// size of s98 header + device info
return false;
}
uint32_t devicetype = read32le(s98data, 0x20);
if (devicetype != 0x04 && devicetype != 0x02) {
// OPN / OPNA only
return false;
}
clock = read32le(s98data, 0x24);
// convert OPN clock to OPNA clock
if (devicetype == 2) clock *= 2;
}
s98->s98data = s98data;
s98->s98data_size = s98data_size;
s98->current_offset = read32le(s98data, 0x14);
s98->opnaclock = clock;
s98->samples_to_generate = 0;
s98->samples_to_generate_frac = 0;
s98->timer_numerator = read32le(s98data, 0x04);
s98->timer_denominator = read32le(s98data, 0x08);
if (!s98->timer_numerator) s98->timer_numerator = 10;
if (!s98->timer_denominator) s98->timer_denominator = 1000;
opna_reset(&s98->opna);
return true;
}
// returns 0 when failed
static size_t s98gen_getvv(struct s98gen *s98) {
unsigned shift = 0;
size_t value = 0;
do {
if (s98->s98data_size < (s98->current_offset+1)) return 0;
value |= (s98->s98data[s98->current_offset] & 0x7f) << ((shift++)*7);
} while (s98->s98data[s98->current_offset++] & 0x80);
return value + 2;
}
static void s98gen_set_samples_to_generate(struct s98gen *s98, size_t ticks) {
uint64_t s = s98->opnaclock * s98->timer_numerator * ticks;
s <<= 16;
s /= 144 * s98->timer_denominator;
s += s98->samples_to_generate_frac;
s98->samples_to_generate = s >> 16;
s98->samples_to_generate_frac = s & ((((size_t)1)<<16)-1);
}
static bool s98gen_parse_s98(struct s98gen *s98) {
for (;;) {
switch (s98->s98data[s98->current_offset]) {
case 0x00:
if (s98->s98data_size < (s98->current_offset + 3)) return false;
opna_writereg(&s98->opna,
s98->s98data[s98->current_offset+1],
s98->s98data[s98->current_offset+2]);
s98->current_offset += 3;
break;
case 0x01:
if (s98->s98data_size < (s98->current_offset + 3)) return false;
opna_writereg(&s98->opna,
s98->s98data[s98->current_offset+1] | 0x100,
s98->s98data[s98->current_offset+2]);
s98->current_offset += 3;
break;
case 0xfe:
if (s98->s98data_size < (s98->current_offset+1)) return false;
s98->current_offset++;
{
size_t vv = s98gen_getvv(s98);
if (!vv) return false;
s98gen_set_samples_to_generate(s98, vv);
}
return true;
case 0xff:
if (s98->s98data_size < (s98->current_offset + 1)) return false;
s98->current_offset++;
s98gen_set_samples_to_generate(s98, 1);
return true;
default:
return false;
}
}
}
bool s98gen_generate(struct s98gen *s98, int16_t *buf, size_t samples) {
for (size_t i = 0; i < samples; i++) {
buf[i*2+0] = 0;
buf[i*2+1] = 0;
}
if (samples <= s98->samples_to_generate) {
opna_mix(&s98->opna, buf, samples);
s98->samples_to_generate -= samples;
} else {
opna_mix(&s98->opna, buf, s98->samples_to_generate);
buf += s98->samples_to_generate * 2;
samples -= s98->samples_to_generate;
s98->samples_to_generate = 0;
while (samples) {
if (!s98gen_parse_s98(s98)) return false;
if (s98->samples_to_generate >= samples) {
opna_mix(&s98->opna, buf, samples);
s98->samples_to_generate -= samples;
samples = 0;
} else {
opna_mix(&s98->opna, buf, s98->samples_to_generate);
buf += s98->samples_to_generate*2;
samples -= s98->samples_to_generate;
s98->samples_to_generate = 0;
}
}
}
return true;
}
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