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bsnes/nall/cd/session.hpp

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#pragma once
//subchannel processor
//note: this code is not tolerant to subchannel data that violates the Redbook standard
namespace nall::CD {
enum : int { InvalidLBA = 100 * 60 * 75 };
struct BCD {
static auto encode(uint8_t value) -> uint8_t { return value / 10 << 4 | value % 10; }
static auto decode(uint8_t value) -> uint8_t { return (value >> 4) * 10 + (value & 15); }
};
struct MSF {
uint8_t minute; //00-99
uint8_t second; //00-59
uint8_t frame = -1; //00-74
MSF() = default;
MSF(uint8_t m, uint8_t s, uint8_t f) : minute(m), second(s), frame(f) {}
MSF(int lba) { *this = fromLBA(lba); }
explicit operator bool() const {
return minute <= 99 && second <= 59 && frame <= 74;
}
static auto fromBCD(uint8_t minute, uint8_t second, uint8_t frame) -> MSF {
return {BCD::decode(minute), BCD::decode(second), BCD::decode(frame)};
}
static auto fromLBA(int lba) -> MSF {
if(lba < 0) lba = 100 * 60 * 75 + lba;
if(lba >= 100 * 60 * 75) return {};
uint8_t minute = lba / 75 / 60 % 100;
uint8_t second = lba / 75 % 60;
uint8_t frame = lba % 75;
return {minute, second, frame};
}
auto toLBA() const -> int {
int lba = minute * 60 * 75 + second * 75 + frame;
if(minute < 90) return lba;
return -(100 * 60 * 75 - lba);
}
//for debugging purposes
auto toString() const -> string {
if(!operator bool()) return "??:??:??";
return {pad(minute, 2, '0'), ":", pad(second, 2, '0'), ":", pad(frame, 2, '0')};
}
};
struct Index {
int lba = InvalidLBA;
int end = InvalidLBA; //inclusive range
explicit operator bool() const {
return lba != InvalidLBA;
}
auto inRange(int sector) const -> bool {
if(lba == InvalidLBA || end == InvalidLBA) return false;
return sector >= lba && sector <= end;
}
};
struct Track {
uint8_t control = 0b1111; //4-bit
uint8_t address = 0b1111; //4-bit
Index indices[100];
uint8_t firstIndex = -1;
uint8_t lastIndex = -1;
explicit operator bool() const {
return (bool)indices[1];
}
auto emphasis() const -> bool {
return control & 1;
}
auto copyable() const -> bool {
return control & 2;
}
auto channels() const -> uint {
if((control & 0b1100) == 0b0000) return 2;
if((control & 0b1100) == 0b1000) return 4;
return 0; //data track or reserved
}
auto pregap() const -> int {
if(!indices[0] || !indices[1]) return InvalidLBA;
return indices[1].lba - indices[0].lba;
}
auto isAudio() const -> bool {
return channels() != 0;
}
auto isData() const -> bool {
return (control & 0b1100) == 0b0100;
}
auto inIndex(int lba) const -> maybe<uint8_t> {
for(uint8_t index : range(100)) {
if(indices[index].inRange(lba)) return index;
}
return {};
}
auto inRange(int lba) const -> bool {
if(firstIndex > 99 || lastIndex > 99) return false;
return lba >= indices[firstIndex].lba && lba <= indices[lastIndex].end;
}
};
struct Session {
Index leadIn; //00
Track tracks[100]; //01-99
Index leadOut; //aa
uint8_t firstTrack = -1;
uint8_t lastTrack = -1;
auto inLeadIn(int lba) const -> bool {
return lba < 0;
}
auto inTrack(int lba) const -> maybe<uint8_t> {
for(uint8_t trackID : range(100)) {
auto& track = tracks[trackID];
if(track && track.inRange(lba)) return trackID;
}
return {};
}
auto inLeadOut(int lba) const -> bool {
return lba >= leadOut.lba;
}
auto encode(uint sectors) const -> vector<uint8_t> {
if(sectors < abs(leadIn.lba) + leadOut.lba) return {}; //not enough sectors
vector<uint8_t> data;
data.resize(sectors * 96 + 96); //add one sector for P shift
auto toP = [&](int lba) -> array_span<uint8_t> {
//P is encoded one sector later than Q
return {&data[(lba + abs(leadIn.lba) + 1) * 96], 12};
};
auto toQ = [&](int lba) -> array_span<uint8_t> {
return {&data[(lba + abs(leadIn.lba)) * 96 + 12], 12};
};
//lead-in
int lba = leadIn.lba;
while(lba < 0) {
//tracks
for(uint trackID : range(100)) {
for(uint repeat : range(3)) {
auto& track = tracks[trackID];
if(!track) continue;
auto q = toQ(lba);
q[0] = track.control << 4 | track.address << 0;
q[1] = 0x00;
q[2] = BCD::encode(trackID);
auto msf = MSF(lba);
q[3] = BCD::encode(msf.minute);
q[4] = BCD::encode(msf.second);
q[5] = BCD::encode(msf.frame);
q[6] = 0x00;
msf = MSF(track.indices[1].lba);
q[7] = BCD::encode(msf.minute);
q[8] = BCD::encode(msf.second);
q[9] = BCD::encode(msf.frame);
auto crc16 = CRC16({q, 10});
q[10] = crc16 >> 8;
q[11] = crc16 >> 0;
if(++lba >= 0) break;
}}if( lba >= 0) break;
//first track
for(uint repeat : range(3)) {
auto q = toQ(lba);
q[0] = 0x01; //control value unverified; address = 1
q[1] = 0x00; //track# = 00 (TOC)
q[2] = 0xa0; //first track
auto msf = MSF(lba);
q[3] = BCD::encode(msf.minute);
q[4] = BCD::encode(msf.second);
q[5] = BCD::encode(msf.frame);
q[6] = 0x00;
q[7] = BCD::encode(firstTrack);
q[8] = 0x00;
q[9] = 0x00;
auto crc16 = CRC16({q, 10});
q[10] = crc16 >> 8;
q[11] = crc16 >> 0;
if(++lba >= 0) break;
} if( lba >= 0) break;
//last track
for(uint repeat : range(3)) {
auto q = toQ(lba);
q[0] = 0x01;
q[1] = 0x00;
q[2] = 0xa1; //last track
auto msf = MSF(lba);
q[3] = BCD::encode(msf.minute);
q[4] = BCD::encode(msf.second);
q[5] = BCD::encode(msf.frame);
q[6] = 0x00;
q[7] = BCD::encode(lastTrack);
q[8] = 0x00;
q[9] = 0x00;
auto crc16 = CRC16({q, 10});
q[10] = crc16 >> 8;
q[11] = crc16 >> 0;
if(++lba >= 0) break;
} if( lba >= 0) break;
//lead-out point
for(uint repeat : range(3)) {
auto q = toQ(lba);
q[0] = 0x01;
q[1] = 0x00;
q[2] = 0xa2; //lead-out point
auto msf = MSF(lba);
q[3] = BCD::encode(msf.minute);
q[4] = BCD::encode(msf.second);
q[5] = BCD::encode(msf.frame);
q[6] = 0x00;
msf = MSF(leadOut.lba);
q[7] = BCD::encode(msf.minute);
q[8] = BCD::encode(msf.second);
q[9] = BCD::encode(msf.frame);
auto crc16 = CRC16({q, 10});
q[10] = crc16 >> 8;
q[11] = crc16 >> 0;
if(++lba >= 0) break;
} if( lba >= 0) break;
}
//tracks
int end = leadOut.lba;
for(uint8_t trackID : reverse(range(100))) {
auto& track = tracks[trackID];
if(!track) continue;
//indices
for(uint8_t indexID : reverse(range(100))) {
auto& index = track.indices[indexID];
if(!index) continue;
for(int lba = index.lba; lba < end; lba++) {
auto p = toP(lba);
uint8_t byte = indexID == 0 ? 0xff : 0x00;
for(uint index : range(12)) p[index] = byte;
auto q = toQ(lba);
q[0] = track.control << 4 | track.address << 0;
q[1] = BCD::encode(trackID);
q[2] = BCD::encode(indexID);
auto msf = MSF(lba - track.indices[1].lba);
q[3] = BCD::encode(msf.minute);
q[4] = BCD::encode(msf.second);
q[5] = BCD::encode(msf.frame);
q[6] = 0x00;
msf = MSF(lba);
q[7] = BCD::encode(msf.minute);
q[8] = BCD::encode(msf.second);
q[9] = BCD::encode(msf.frame);
auto crc16 = CRC16({q, 10});
q[10] = crc16 >> 8;
q[11] = crc16 >> 0;
}
end = index.lba;
}
}
//lead-out
for(int lba : range(sectors - abs(leadIn.lba) - leadOut.lba)) {
auto p = toP(leadOut.lba + lba);
uint8_t byte;
if(lba < 150) {
//2s start (standard specifies 2-3s start)
byte = 0x00;
} else {
//2hz duty cycle; rounded downward (standard specifies 2% tolerance)
byte = (lba - 150) / (75 >> 1) & 1 ? 0xff : 0x00;
}
for(uint index : range(12)) p[index] = byte;
auto q = toQ(leadOut.lba + lba);
q[0] = 0x01;
q[1] = 0xaa; //lead-out track#
q[2] = 0x01; //lead-out index#
auto msf = MSF(lba);
q[3] = BCD::encode(msf.minute);
q[4] = BCD::encode(msf.second);
q[5] = BCD::encode(msf.frame);
q[6] = 0x00;
msf = MSF(leadOut.lba + lba);
q[7] = BCD::encode(msf.minute);
q[8] = BCD::encode(msf.second);
q[9] = BCD::encode(msf.frame);
auto crc16 = CRC16({q, 10});
q[10] = crc16 >> 8;
q[11] = crc16 >> 0;
}
data.resize(data.size() - 96); //remove padding for P shift
return data;
}
auto decode(array_view<uint8_t> data, uint size, uint leadOutSectors = 0) -> bool {
*this = {}; //reset session
//three data[] types supported: subcode Q only, subcode P-W only, data+subcode complete image
if(size != 12 && size != 96 && size != 2448) return false;
//determine lead-in sector count
for(int lba : range(7500)) { //7500 max sectors scanned
uint offset = lba * size;
if(size == 96) offset += 12;
if(size == 2448) offset += 12 + 2352;
if(offset + 12 > data.size()) break;
auto q = array_view<uint8_t>{&data[offset], 12};
auto crc16 = CRC16({q, 10});
if(q[10] != uint8_t(crc16 >> 8)) continue;
if(q[11] != uint8_t(crc16 >> 0)) continue;
uint8_t control = q[0] >> 4;
uint8_t address = q[0] & 15;
uint8_t trackID = q[1];
if(address != 1) continue;
if(trackID != 0) continue;
auto msf = MSF::fromBCD(q[3], q[4], q[5]);
leadIn.lba = msf.toLBA() - lba;
break;
}
if(leadIn.lba == InvalidLBA || leadIn.lba >= 0) return false;
auto toQ = [&](int lba) -> array_view<uint8_t> {
uint offset = (lba + abs(leadIn.lba)) * size;
if(size == 96) offset += 12;
if(size == 2448) offset += 12 + 2352;
if(offset + 12 > data.size()) return {};
return {&data[offset], 12};
};
//lead-in
for(int lba = leadIn.lba; lba < 0; lba++) {
auto q = toQ(lba);
if(!q) break;
auto crc16 = CRC16({q, 10});
if(q[10] != uint8_t(crc16 >> 8)) continue;
if(q[11] != uint8_t(crc16 >> 0)) continue;
uint8_t control = q[0] >> 4;
uint8_t address = q[0] & 15;
uint8_t trackID = q[1];
if(address != 1) continue;
if(trackID != 0) continue;
trackID = BCD::decode(q[2]);
if(trackID <= 99) { //00-99
auto& track = tracks[trackID];
track.control = control;
track.address = address;
track.indices[1].lba = MSF::fromBCD(q[7], q[8], q[9]).toLBA();
}
if(trackID == 100) { //a0
firstTrack = BCD::decode(q[7]);
}
if(trackID == 101) { //a1
lastTrack = BCD::decode(q[7]);
}
if(trackID == 102) { //a2
leadOut.lba = MSF::fromBCD(q[7], q[8], q[9]).toLBA();
}
}
if(leadOut.lba == InvalidLBA) return false;
//tracks
for(int lba = 0; lba < leadOut.lba; lba++) {
auto q = toQ(lba);
if(!q) break;
auto crc16 = CRC16({q, 10});
if(q[10] != uint8_t(crc16 >> 8)) continue;
if(q[11] != uint8_t(crc16 >> 0)) continue;
uint8_t control = q[0] >> 4;
uint8_t address = q[0] & 15;
uint8_t trackID = BCD::decode(q[1]);
uint8_t indexID = BCD::decode(q[2]);
if(address != 1) continue;
if(trackID > 99) continue;
if(indexID > 99) continue;
auto& track = tracks[trackID];
if(!track) continue; //track not found?
auto& index = track.indices[indexID];
if(index) continue; //index already decoded?
index.lba = MSF::fromBCD(q[7], q[8], q[9]).toLBA();
}
synchronize(leadOutSectors);
return true;
}
//calculates Index::end variables:
//needed for Session::isTrack() and Track::isIndex() to function.
auto synchronize(uint leadOutSectors = 0) -> void {
leadIn.end = -1;
int end = leadOut.lba - 1;
for(uint trackID : reverse(range(100))) {
auto& track = tracks[trackID];
if(!track) continue;
for(uint indexID : reverse(range(100))) {
auto& index = track.indices[indexID];
if(!index) continue;
index.end = end;
end = index.lba - 1;
}
for(uint indexID : range(100)) {
auto& index = track.indices[indexID];
if(index) { track.firstIndex = indexID; break; }
}
for(uint indexID : reverse(range(100))) {
auto& index = track.indices[indexID];
if(index) { track.lastIndex = indexID; break; }
}
}
leadOut.end = leadOut.lba + leadOutSectors - 1;
}
//for diagnostic use only
auto serialize() const -> string {
string s;
s.append("session\n");
s.append(" leadIn: ");
s.append(MSF(leadIn.lba).toString(), " - ", MSF(leadIn.end).toString(), "\n");
for(uint trackID : range(100)) {
auto& track = tracks[trackID];
if(!track) continue;
s.append(" track", pad(trackID, 2, '0'));
if(trackID == firstTrack) s.append(" first");
if(trackID == lastTrack) s.append( " last");
s.append("\n");
s.append(" control: ", binary(track.control, 4, '0'), "\n");
s.append(" address: ", binary(track.address, 4, '0'), "\n");
for(uint indexID : range(100)) {
auto& index = track.indices[indexID];
if(!index) continue;
s.append(" index", pad(indexID, 2, '0'), ": ");
s.append(MSF(index.lba).toString(), " - ", MSF(index.end).toString(), "\n");
}
}
s.append(" leadout: ");
s.append(MSF(leadOut.lba).toString(), " - ", MSF(leadOut.end).toString(), "\n");
return s;
}
};
}
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