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373244024x 373244024x 373244024x 373244024x 373244024x 46655503x 3157048x 24911x 41339989x 41339989x 330719912x 330719912x 330719912x 330719912x 330719912x 41339989x 25829881x 25829881x 25829881x 25829881x 206639048x 206639048x 206639048x 206639048x 206639048x 206639048x 25829881x 2281148x 2281148x 18249184x 18249184x 18249184x 18249184x 15668824x 18249184x 2281148x 35957x 35957x 287656x 287656x 287656x 35957x 47x 41x 27x | // Translated from beebjit by Chris Evans.
// https://github.com/scarybeasts/beebjit
import { crc32 } from "./archive.js";
import { hexbyte } from "./hex.js";
export const PulsesPerWord = 32;
class TrackBuilder {
/**
* @param {Track} track
*/
constructor(track) {
this._track = track;
this._track.length = IbmDiscFormat.bytesPerTrack;
this._index = 0;
this._pulsesIndex = 0;
this._lastMfmBit = 0;
this._isMfm = false;
this._crc = 0;
}
get track() {
return this._track;
}
setTrackLength() {
Iif (this._index > this._track.pulses2Us.length)
throw new Error(`Track buffer overflow in ${this._track.description}`);
Eif (this._index !== 0) this._track.length = this._index;
return this;
}
resetCrc() {
this._crc = IbmDiscFormat.crcInit(false);
return this;
}
appendFmDataAndClocks(data, clocks) {
Iif (this._index >= this._track.pulses2Us.length)
throw new Error(`Track buffer overflow in ${this._track.description}`);
this._track.pulses2Us[this._index++] = IbmDiscFormat.fmTo2usPulses(clocks, data);
this._isMfm = false;
this._crc = IbmDiscFormat.crcAddByte(this._crc, data);
return this;
}
appendFmByte(data) {
this.appendFmDataAndClocks(data, 0xff);
return this;
}
appendRepeatFmByte(data, count) {
for (let i = 0; i < count; ++i) this.appendFmByte(data);
return this;
}
fillFmByte(data) {
Iif (this._index >= this._track.pulses2Us.length)
throw new Error(`Track buffer overflow in ${this._track.description}`);
// Fill to standard track size or buffer capacity, whichever is smaller
const fillCount = Math.min(IbmDiscFormat.bytesPerTrack, this._track.pulses2Us.length) - this._index;
this.appendRepeatFmByte(data, fillCount);
return this;
}
appendRepeatFmByteWithClocks(data, clocks, count) {
for (let i = 0; i < count; ++i) this.appendFmDataAndClocks(data, clocks);
return this;
}
appendFmChunk(bytes) {
for (const byte of bytes) this.appendFmByte(byte);
return this;
}
appendCrc() {
const firstByte = (this._crc >>> 8) & 0xff;
const secondByte = this._crc & 0xff;
if (this._isMfm) {
this.appendMfmByte(firstByte);
this.appendMfmByte(secondByte);
} else {
this.appendFmByte(firstByte);
this.appendFmByte(secondByte);
}
return this;
}
appendMfmPulses(pulses) {
Iif (this._index >= this._track.pulses2Us.length)
throw new Error(`Track buffer overflow in ${this._track.description}`);
const existingPulses = this._track.pulses2Us[this._index];
const mask = 0xffff << this._pulsesIndex;
this._pulsesIndex = (this._pulsesIndex + 16) & 31;
this._track.pulses2Us[this._index] = (existingPulses & mask) | (pulses << this._pulsesIndex);
if (this._pulsesIndex === 0) this._index++;
this._isMfm = true;
return this;
}
appendMfmByte(data) {
const { lastBit, pulses } = IbmDiscFormat.mfmTo2usPulses(this._lastMfmBit, data);
this._lastMfmBit = lastBit;
this.appendMfmPulses(pulses);
this._crc = IbmDiscFormat.crcAddByte(this._crc, data);
return this;
}
appendRepeatMfmByte(data, count) {
for (let i = 0; i < count; ++i) this.appendMfmByte(data);
return this;
}
appendMfm3xA1Sync() {
for (let i = 0; i < 3; ++i) {
this.appendMfmPulses(IbmDiscFormat.mfmA1Sync);
this._crc = IbmDiscFormat.crcAddByte(this._crc, 0xa1);
}
return this;
}
appendMfmChunk(bytes) {
for (const byte of bytes) this.appendMfmByte(byte);
return this;
}
fillMfmByte(data) {
Iif (this._index >= this._track.pulses2Us.length)
throw new Error(`Track buffer overflow in ${this._track.description}`);
// Fill to standard track size or buffer capacity, whichever is smaller
const maxFill = Math.min(IbmDiscFormat.bytesPerTrack, this._track.pulses2Us.length);
while (this._index < maxFill) this.appendMfmByte(data);
return this;
}
/**
* @param {number[]} pulseDeltas array of lengths between pulses
* @param {boolean} isMfm whether this is an MFM track
*/
buildFromPulses(pulseDeltas, isMfm) {
this._isMfm = isMfm;
let hasWarned = false;
for (const pulse of pulseDeltas) {
Iif (!IbmDiscFormat.checkPulse(pulse, isMfm)) {
console.log(`Found a bad pulse for ${this.track.description}`);
}
Iif (!this.appendPulseDelta(pulse, isMfm) && !hasWarned) {
console.log(`Truncated disc data for ${this.track.description}, ignoring the rest`);
hasWarned = true;
}
}
this.setTrackLength();
}
appendPulseDelta(deltaUs, quantizeMfm) {
let num2UsUnits = quantizeMfm ? Math.round(deltaUs / 2) : 2 * Math.round(deltaUs / 4);
while (num2UsUnits--) {
Iif (this._index >= this._track.pulses2Us.length) return false;
if (num2UsUnits === 0) {
this._track.pulses2Us[this._index] |= 0x80000000 >>> this._pulsesIndex;
}
this._pulsesIndex++;
if (this._pulsesIndex === 32) {
this._pulsesIndex = 0;
this._index++;
}
}
return true;
}
}
class RawDiscReader {
/**
* @param {Track} track
* @param {Number} bitOffset
*/
constructor(track, bitOffset) {
this._track = track;
this._pos = bitOffset;
}
readPulses() {
let pulsesPos = this._pos >>> 5;
const bitPos = this._pos & 0x1f;
let sourcePulses = this._track.pulses2Us[pulsesPos];
let pulses = (sourcePulses << bitPos) & 0xfffffffff;
Iif (pulsesPos === this._track.length) {
pulsesPos = 0;
this._pos = bitPos;
} else {
pulsesPos++;
this._pos += 32;
}
if (bitPos > 0) {
sourcePulses = this._track.pulses2Us[pulsesPos];
pulses |= sourcePulses >>> (32 - bitPos);
}
return pulses;
}
}
class MfmReader {
/**
* @param {RawDiscReader} rawReader
*/
constructor(rawReader) {
this._rawReader = rawReader;
}
static get pulsesPerByte() {
return 16;
}
read(numBytes) {
const data = new Uint8Array(numBytes);
let pulses = 0;
for (let offset = 0; offset < numBytes; ++offset) {
if ((offset & 1) === 0) {
pulses = this._rawReader.readPulses();
} else {
pulses = (pulses << 16) & 0xffffffff;
}
data[offset] = IbmDiscFormat._2usPulsesToMfm(pulses >>> 16);
}
return { data, iffyPulses: false };
}
get initialCrc() {
let crc = IbmDiscFormat.crcInit(false);
crc = IbmDiscFormat.crcAddByte(crc, 0xa1);
crc = IbmDiscFormat.crcAddByte(crc, 0xa1);
crc = IbmDiscFormat.crcAddByte(crc, 0xa1);
return crc;
}
}
class FmReader {
/**
* @param {RawDiscReader} rawReader
*/
constructor(rawReader) {
this._rawReader = rawReader;
}
static get pulsesPerByte() {
return 32;
}
read(numBytes) {
const data = new Uint8Array(numBytes);
let iffyPulses = false;
for (let offset = 0; offset < numBytes; ++offset) {
const pulses = this._rawReader.readPulses();
const { data: dataByte, iffyPulses: iffy } = IbmDiscFormat._2usPulsesToFm(pulses);
data[offset] = dataByte;
iffyPulses |= iffy;
}
return { data, iffyPulses };
}
get initialCrc() {
return IbmDiscFormat.crcInit(false);
}
}
class Sector {
/**
* @param {Track} track
* @param {boolean} isMfm
* @param {Number} idPosBitOffset
* @param {function(string): void} [warn] where to report anomalies; the console by default
*/
constructor(track, isMfm, idPosBitOffset, warn = console.log) {
this.track = track;
this.isMfm = isMfm;
this._readerType = isMfm ? MfmReader : FmReader;
this._warn = warn;
this.idPosBitOffset = idPosBitOffset;
this.dataPosBitOffset = null;
this.isDeleted = false;
this.sectorData = null;
this.hasDataCrcError = false;
this.byteLength = null;
const idReader = this._readerAt(this.idPosBitOffset);
const { data: headerData, iffyPulses } = idReader.read(6);
if (iffyPulses) {
this._warn(`Iffy pulse in sector header ${this.description}`);
}
this.header = headerData;
let crc = idReader.initialCrc;
crc = IbmDiscFormat.crcAddByte(crc, IbmDiscFormat.idMarkDataPattern);
crc = IbmDiscFormat.crcAddBytes(crc, this.header.slice(0, 4));
const discCrc = (this.header[4] << 8) | this.header[5];
this.hasHeaderCrcError = crc !== discCrc;
}
_readerAt(bitOffset) {
return new this._readerType(new RawDiscReader(this.track, bitOffset));
}
get pulsesPerByte() {
return this._readerType.pulsesPerByte;
}
get trackNumber() {
return this.header ? this.header[0] : undefined;
}
get sectorNumber() {
return this.header ? this.header[2] : undefined;
}
get description() {
return `${this.track.description} idpos ${this.idPosBitOffset} idtrack ${this.trackNumber} idsector ${this.sectorNumber} datapos ${this.dataPosBitOffset}`;
}
/**
* @param {Sector|undefined} nextSector
*/
read(nextSector) {
if (this.dataPosBitOffset === null) {
this._warn(`Sector header without data ${this.description}`);
return;
}
const { pulsesPerByte } = this;
const dataMarker = this.isDeleted
? IbmDiscFormat.deletedDataMarkDataPattern
: IbmDiscFormat.dataMarkDataPattern;
const sectorStartByte = (this.dataPosBitOffset / pulsesPerByte) | 0;
const sectorEndByte =
(nextSector
? nextSector.idPosBitOffset / pulsesPerByte
: (this.track.length * PulsesPerWord) / pulsesPerByte) | 0;
// Account for CRC and sync bytes.
let sectorSize = Sector.toSectorSize(sectorEndByte - sectorStartByte - 5);
this.hasDataCrcError = true;
let seenIffyData;
do {
const { crcOk, sectorData, iffyPulses } = this._tryLoadSectorData(dataMarker, sectorSize);
seenIffyData = iffyPulses;
if (crcOk) {
this.byteLength = sectorSize;
this.hasDataCrcError = false;
this.sectorData = sectorData;
break;
}
sectorSize = sectorSize >>> 1;
} while (sectorSize >= 128);
if (seenIffyData) {
this._warn(`Iffy pulse in sector data ${this.description}`);
}
}
_tryLoadSectorData(dataMarker, sectorSize) {
const dataReader = this._readerAt(this.dataPosBitOffset);
let crc = IbmDiscFormat.crcAddByte(dataReader.initialCrc, dataMarker);
const { data: sectorData, iffyPulses } = dataReader.read(sectorSize + 2);
crc = IbmDiscFormat.crcAddBytes(crc, sectorData.slice(0, sectorSize));
const dataCrc = (sectorData[sectorSize] << 8) | sectorData[sectorSize + 1];
// The CRC bytes are used for error-checking and are not part of the actual sector data payload.
// Therefore, we exclude the last two bytes (CRC) from the returned `sectorData`.
return { crcOk: dataCrc === crc, sectorData: sectorData.slice(0, sectorSize), iffyPulses };
}
static toSectorSize(size) {
Iif (size < 256) return 128;
if (size < 512) return 256;
if (size < 1024) return 512;
Iif (size < 2048) return 1024;
return 2048;
}
}
/**
* A 64 bit shift register, held as a pair of unsigned 32 bit halves. BigInt would say this more
* directly but costs an order of magnitude more per bit shifted.
*/
export class BitWindow64 {
constructor() {
this.hi = 0;
this.lo = 0;
}
/**
* @param {Number} bit 0 or 1, shifted into bit 0
* @returns {Number} the bit shifted out of bit 63
*/
shiftIn(bit) {
const shiftedOut = this.hi >>> 31;
this.hi = ((this.hi << 1) | (this.lo >>> 31)) >>> 0;
this.lo = ((this.lo << 1) | bit) >>> 0;
return shiftedOut;
}
/**
* @returns {boolean} whether all 64 bits match the halves given
*/
equals(hi, lo) {
return this.hi === hi && this.lo === lo;
}
/**
* @param {Number} nibble
* @returns {Number} the length of the run of `nibble` ending at bit 0
*/
countTrailingNibbles(nibble) {
const nibblesPerHalf = 8;
let count = 0;
for (let bits = this.lo; (bits & 0xf) === nibble; bits >>>= 4) count++;
// Only a low half that matched all the way up can have a run continuing into the high half.
if (count === nibblesPerHalf) for (let bits = this.hi; (bits & 0xf) === nibble; bits >>>= 4) count++;
return count;
}
}
// What the mark detector holds at an address mark. The FM case only pins down the high half,
// the tail of the zero sync run; the low half is the marker byte itself, decoded separately.
const FmSyncHi = 0x88888888;
const MfmMarkerHi = 0xaaaa4489;
const MfmMarkerLo = 0x44894489;
// One data bit of zero, FM encoded with its clock, is the pulse nibble 0x8.
const FmZeroBitPulses = 0x8;
// FmSyncHi is eight of those, so a match has already seen this much of the sync run.
const FmSyncHiZeroBits = 8;
// Sync is counted in zero data bits, so a run no longer than two bytes' worth is short enough
// to be worth logging.
const ShortSyncZeros = 16;
class Track {
constructor(upper, trackNum, initialByte) {
this.length = IbmDiscFormat.bytesPerTrack; // Default size, will be updated when track is populated
this.upper = upper;
this.trackNum = trackNum;
// Make room for any extra pulses that might come from non-standard discs.
this.pulses2Us = new Uint32Array(IbmDiscFormat.bytesPerTrack * 2);
this.pulses2Us.fill(initialByte | (initialByte << 8) | (initialByte << 16) | (initialByte << 24));
}
get description() {
return `Track ${this.trackNum} ${this.upper ? "upper" : "lower"}`;
}
/**
* Debug functionality to try and interpret the track.
* @param {function(string): void} [warn] where to report anomalies; the console by default
* @returns {Sector[]}
*/
findSectors(warn = console.log) {
const sectors = this.findSectorIds(warn);
for (let sectorIndex = 0; sectorIndex !== sectors.length; ++sectorIndex) {
const nextSector = sectors[sectorIndex + 1]; // Will be unset for last
sectors[sectorIndex].read(nextSector);
}
return sectors;
}
/**
* @param {function(string): void} [warn] where to report anomalies; the console by default
* @returns {Sector[]}
*/
findSectorIds(warn = console.log) {
const sectors = [];
// Pass 1: walk the track and find header and data markers.
const bitLength = this.length * 32;
let shiftRegister = 0;
let numShifts = 0;
let doMfmMarkerByte = false;
let isMfm = false;
let pulses = 0;
// The mark detector is a 64 bit sliding window over the pulse stream; the bits leaving it
// spill into a second window, which the sync run length is counted from.
const markDetector = new BitWindow64();
const markDetectorPrev = new BitWindow64();
let dataByte;
let sector = null;
for (let pulseIndex = 0; pulseIndex < bitLength; ++pulseIndex) {
if ((pulseIndex & 31) === 0) pulses = this.pulses2Us[pulseIndex >>> 5];
const pulseBit = pulses >>> 31;
markDetectorPrev.shiftIn(markDetector.shiftIn(pulseBit));
shiftRegister = ((shiftRegister << 1) | pulseBit) & 0xffffffff;
numShifts++;
pulses = (pulses << 1) & 0xffffffff;
if (markDetector.hi === FmSyncHi) {
const { clocks, data, iffyPulses } = IbmDiscFormat._2usPulsesToFm(markDetector.lo);
if (iffyPulses || clocks !== IbmDiscFormat.markClockPattern) continue;
isMfm = false;
doMfmMarkerByte = false;
const num0s = FmSyncHiZeroBits + markDetectorPrev.countTrailingNibbles(FmZeroBitPulses);
Iif (num0s <= ShortSyncZeros) {
warn(`Short zeros sync ${this.description}`);
}
dataByte = data;
} else if (markDetector.equals(MfmMarkerHi, MfmMarkerLo)) {
// Next byte is MFM marker.
isMfm = true;
doMfmMarkerByte = true;
shiftRegister = 0;
numShifts = 0;
continue;
} else if (doMfmMarkerByte && numShifts === 16) {
dataByte = IbmDiscFormat._2usPulsesToMfm(shiftRegister);
doMfmMarkerByte = false;
} else {
continue;
}
switch (dataByte) {
case IbmDiscFormat.idMarkDataPattern: {
sector = new Sector(this, isMfm, pulseIndex + 1, warn);
sectors.push(sector);
shiftRegister = 0;
numShifts = 0;
break;
}
case IbmDiscFormat.dataMarkDataPattern:
case IbmDiscFormat.deletedDataMarkDataPattern:
Iif (!sector || sector.dataPosBitOffset) {
warn(
`Sector data without header ${this.description}; mark bitpos ${pulseIndex}; previous good sector ${sector ? sector.description : "none"}`,
);
} else {
sector.dataPosBitOffset = pulseIndex + 1;
if (dataByte === IbmDiscFormat.deletedDataMarkDataPattern) {
sector.isDeleted = true;
}
shiftRegister = 0;
numShifts = 0;
}
break;
default:
warn(`Unknown marker byte ${hexbyte(dataByte)} ${this.description}`);
}
}
return sectors;
}
}
class Side {
constructor(upper, initialByte) {
this.tracks = [];
for (let i = 0; i < IbmDiscFormat.tracksPerDisc; ++i) this.tracks[i] = new Track(upper, i, initialByte);
}
}
/** How an image's tracks are laid out on the surface, and whether that is for the loader to decide. */
export const DiscLayout = Object.freeze({
auto: "auto",
contiguous: "contiguous",
expanded40: "expanded40",
});
export class DiscConfig {
constructor() {
this.expandTo80 = false;
this.isSkipOddTracks = false;
this.isSkipUpperSide = false;
}
}
class SsdFormat {
static get sectorSize() {
return 256;
}
static get sectorsPerTrack() {
return 10;
}
static get tracksPerDisc() {
return 80;
}
static get trackSize() {
return SsdFormat.sectorSize * SsdFormat.sectorsPerTrack;
}
}
/** @returns {Number} how many logical tracks of `data` hold anything, ignoring a run of trailing zeros */
function tracksWithData(data, numSides) {
let lastUsed = data.length - 1;
while (lastUsed >= 0 && data[lastUsed] === 0) lastUsed--;
return Math.floor(lastUsed / (SsdFormat.trackSize * numSides)) + 1;
}
// The DFS catalogue is the first two sectors of a side. Sector 1 holds how many files there are and
// how many sectors the disc has.
const DfsEntryCountOffset = 0x105;
const DfsSectorCountOffset = 0x106;
const DfsEntrySize = 8;
const DfsMaxEntries = 31;
/**
* Whether an SSD or DSD image was written by a 40 track drive. Only its catalogue can say: images
* are routinely padded out or cut short, so their size means nothing.
*
* @param {Uint8Array} data
* @param {boolean} isDsd
* @returns {{is40Track: boolean, reason: string}}
*/
export function sniffDfsLayout(data, isDsd) {
const contiguous = (reason) => ({ is40Track: false, reason });
if (data.length < 2 * SsdFormat.sectorSize) return contiguous("it is smaller than a catalogue");
const entryBytes = data[DfsEntryCountOffset];
if (entryBytes % DfsEntrySize !== 0 || entryBytes > DfsMaxEntries * DfsEntrySize)
return contiguous(`its catalogue claims ${entryBytes} bytes of file entries`);
const sectors = ((data[DfsSectorCountOffset] & 3) << 8) | data[DfsSectorCountOffset + 1];
const reason = `its catalogue claims ${sectors} sectors`;
const fortyTrackSectors = (SsdFormat.tracksPerDisc / 2) * SsdFormat.sectorsPerTrack;
if (sectors === 0 || sectors > fortyTrackSectors) return contiguous(reason);
const tracks = tracksWithData(data, isDsd ? 2 : 1);
if (tracks > IbmDiscFormat.tracksPerDisc / 2) return contiguous(`it holds data as far as track ${tracks - 1}`);
return { is40Track: true, reason };
}
// The title is split across the two catalogue sectors, and the cycle number follows its second half.
const DfsTitleFirstHalf = 8;
const DfsTitleSecondHalf = 4;
const DfsCycleOffset = 4;
const DfsEntryCountInSector1 = DfsEntryCountOffset - SsdFormat.sectorSize;
const isPrintableAscii = (byte) => byte >= 0x20 && byte < 0x7f;
/**
* What the DFS catalogue on one side of a loaded disc says it is called, and how many times it
* has been written to, which between them are what was on the sticker.
*
* @param {Disc} disc
* @param {boolean} [isSideUpper]
* @returns {{title: string, cycle: string}|null} null when the side holds no DFS catalogue
*/
export function dfsCatalogue(disc, isSideUpper = false) {
const sectors = new Map();
for (const sector of disc.getTrack(isSideUpper, 0).findSectors(() => {})) {
const usable =
!sector.hasHeaderCrcError && !sector.hasDataCrcError && sector.sectorData?.length === SsdFormat.sectorSize;
if (usable && !sectors.has(sector.sectorNumber)) sectors.set(sector.sectorNumber, sector.sectorData);
}
const sector0 = sectors.get(0);
const sector1 = sectors.get(1);
if (!sector0 || !sector1) return null;
const entryBytes = sector1[DfsEntryCountInSector1];
if (entryBytes % DfsEntrySize !== 0 || entryBytes > DfsMaxEntries * DfsEntrySize) return null;
const titleBytes = [...sector0.subarray(0, DfsTitleFirstHalf), ...sector1.subarray(0, DfsTitleSecondHalf)];
const title = String.fromCharCode(...titleBytes.filter(isPrintableAscii)).trimEnd();
return { title, cycle: hexbyte(sector1[DfsCycleOffset]) };
}
// One track could match by luck; a disc's worth of them could not.
const MinDoubleSteppedTracks = 4;
/**
* Whether a surface holds a 40 track format, going by where its sectors say they are: a track
* written by a 48 tpi head sits at twice the number its own headers claim, with nothing readable
* on the tracks between. Only a flux image can be asked this, since for any other format the
* layout is the loader's own doing.
*
* @param {Disc} disc
* @returns {{is40Track: boolean, reason: string}}
*/
export function sniffSurfaceLayout(disc) {
let doubleStepped = 0;
// Both heads move together, so a disc has one pitch and the side that boots can speak for it.
// Track 0 is where it claims to be at either pitch, so it says nothing.
for (let trackNum = 1; trackNum < disc.tracksUsed; ++trackNum) {
const sectors = disc.getTrack(false, trackNum).findSectorIds(() => {});
if (!sectors.length) continue;
if (trackNum & 1) return { is40Track: false, reason: `track ${trackNum} holds sectors of its own` };
if (sectors.some((sector) => sector.trackNumber === trackNum / 2)) doubleStepped++;
}
if (doubleStepped < MinDoubleSteppedTracks)
return { is40Track: false, reason: `only ${doubleStepped} tracks sit at twice their own number` };
return { is40Track: true, reason: `${doubleStepped} tracks sit at twice the number their sectors claim` };
}
/**
* Load a disc image in SSD (Single Sided Disc) or DSD (Double Sided Disc) format
* @param {Disc} disc - The disc object to load into
* @param {Uint8Array} data - The disc image data
* @param {boolean} isDsd - True if loading a double-sided disc
* @param {function(Uint8Array): void} onChange - Optional callback when disc content changes
*/
export function loadSsd(disc, data, isDsd, onChange) {
const blankSector = new Uint8Array(SsdFormat.sectorSize);
const numSides = isDsd ? 2 : 1;
if (data.length % SsdFormat.sectorSize !== 0) {
const paddedLength = Math.ceil(data.length / SsdFormat.sectorSize) * SsdFormat.sectorSize;
const padded = new Uint8Array(paddedLength);
padded.set(data);
data = padded;
}
const maxSize = SsdFormat.sectorSize * SsdFormat.sectorsPerTrack * SsdFormat.tracksPerDisc * numSides;
Iif (data.length > maxSize) {
throw new Error("SSD file is too large");
}
disc.is40Track = disc.config.expandTo80;
const trackStep = disc.is40Track ? 2 : 1;
// Tracks twice as far apart are half as many, and an image can run past the last of them as
// far as the surface has room for.
const numTracks = Math.min(
IbmDiscFormat.tracksPerDisc / trackStep,
Math.max(SsdFormat.tracksPerDisc / trackStep, tracksWithData(data, numSides)),
);
let offset = 0;
for (let track = 0; track < numTracks; ++track) {
for (let side = 0; side < numSides; ++side) {
const trackBuilder = disc.buildTrack(side === 1, track * trackStep);
// Sync pattern at start of track, as the index pulse starts, aka GAP 5.
trackBuilder
.appendRepeatFmByte(0xff, IbmDiscFormat.stdGap1FFs)
.appendRepeatFmByte(0x00, IbmDiscFormat.stdSync00s);
for (let sector = 0; sector < SsdFormat.sectorsPerTrack; ++sector) {
// Sector header, aka ID.
trackBuilder
.resetCrc()
.appendFmDataAndClocks(IbmDiscFormat.idMarkDataPattern, IbmDiscFormat.markClockPattern)
.appendFmByte(track)
.appendFmByte(0)
.appendFmByte(sector)
.appendFmByte(1)
.appendCrc();
// Sync pattern between sector header and sector data, aka GAP 2.
trackBuilder
.appendRepeatFmByte(0xff, IbmDiscFormat.stdGap2FFs)
.appendRepeatFmByte(0x00, IbmDiscFormat.stdSync00s);
// Sector data.
const sectorData =
offset < data.length ? data.subarray(offset, offset + SsdFormat.sectorSize) : blankSector;
offset += SsdFormat.sectorSize;
trackBuilder
.resetCrc()
.appendFmDataAndClocks(IbmDiscFormat.dataMarkDataPattern, IbmDiscFormat.markClockPattern)
.appendFmChunk(sectorData)
.appendCrc();
if (sector !== SsdFormat.sectorsPerTrack - 1) {
// Sync pattern between sectors, aka GAP 3.
trackBuilder
.appendRepeatFmByte(0xff, IbmDiscFormat.std10SectorGap3FFs)
.appendRepeatFmByte(0x00, IbmDiscFormat.stdSync00s);
}
}
trackBuilder.fillFmByte(0xff);
}
}
if (onChange) {
// TODO(#822) maybe construct the disc directly with this stuff?
// TODO(#822) maybe change this entirely and make it lazy; and have the onChange "pull" the disc as the format it wants
// instead of doing this here. Most stuff doesn't care about changes and only needs the image on save.
// Create a dataCopy large enough for all the sectors and tracks.
const dataCopy = new Uint8Array(maxSize);
dataCopy.set(data);
disc.addTrackWriteListener(
/** @param {Track} trackObj */
(side, _trackNum, trackObj) => {
for (const sector of trackObj.findSectors())
if (!sectorShortfall(sector)) dataCopy.set(sector.sectorData, ssdOffsetOf(sector, side, numSides));
onChange(dataCopy);
},
true,
);
}
return disc;
}
class AdfFormat {
static get sectorSize() {
return 256;
}
static get sectorsPerTrack() {
return 16;
}
static get tracksPerDisc() {
return 80;
}
}
/**
* @param {Disc} disc
* @param {Uint8Array} data
* @param {boolean} isDsd
*/
export function loadAdf(disc, data, isDsd) {
const blankSector = new Uint8Array(AdfFormat.sectorSize);
const numSides = isDsd ? 2 : 1;
Iif (data.length % AdfFormat.sectorSize !== 0) {
throw new Error("ADF file size is not a multiple of sector size");
}
const maxSize = AdfFormat.sectorSize * AdfFormat.sectorsPerTrack * AdfFormat.tracksPerDisc * numSides;
Iif (data.length > maxSize) {
throw new Error("ADF file is too large");
}
let offset = 0;
for (let track = 0; track < AdfFormat.tracksPerDisc; ++track) {
if (offset >= data.length) break;
for (let side = 0; side < numSides; ++side) {
// Using recommended values from the 177x datasheet.
const trackBuilder = disc.buildTrack(side === 1, track);
trackBuilder.appendRepeatMfmByte(0x4e, 60);
for (let sector = 0; sector < AdfFormat.sectorsPerTrack; ++sector) {
trackBuilder
.appendRepeatMfmByte(0x00, 12)
.resetCrc()
.appendMfm3xA1Sync()
.appendMfmByte(IbmDiscFormat.idMarkDataPattern)
.appendMfmByte(track)
.appendMfmByte(0)
.appendMfmByte(sector)
.appendMfmByte(1)
.appendCrc();
// Sync pattern between sector header and sector data, aka GAP 2.
trackBuilder.appendRepeatMfmByte(0x4e, 22).appendRepeatMfmByte(0x00, 12);
// Sector data.
const sectorData =
offset < data.length ? data.subarray(offset, offset + AdfFormat.sectorSize) : blankSector;
offset += AdfFormat.sectorSize;
trackBuilder
.resetCrc()
.appendMfm3xA1Sync()
.appendMfmByte(IbmDiscFormat.dataMarkDataPattern)
.appendMfmChunk(sectorData)
.appendCrc();
// Sync pattern between sectors, aka GAP 3.
trackBuilder.appendRepeatMfmByte(0x4e, 24);
}
trackBuilder.fillMfmByte(0x4e);
}
}
// TODO(#822) writeback
return disc;
}
/** Why a sector will not fit in an SSD or DSD image, or null if it will. */
function sectorShortfall(sector) {
if (sector.hasDataCrcError || sector.hasHeaderCrcError) return "with a CRC error";
// A header whose data mark never arrives leaves the sector with nothing to write.
if (!sector.sectorData) return "with no data";
if (sector.sectorNumber >= SsdFormat.sectorsPerTrack)
return `numbered past the ${SsdFormat.sectorsPerTrack} a track holds`;
Iif (sector.sectorData.length !== SsdFormat.sectorSize) return `not ${SsdFormat.sectorSize} bytes`;
Iif (sector.trackNumber >= SsdFormat.tracksPerDisc) return `past track ${SsdFormat.tracksPerDisc}`;
return null;
}
/**
* Where a sector belongs in an SSD or DSD image, which is the track its own header claims rather
* than the one it sits on.
*
* @param {Sector} sector
* @param {boolean} isSideUpper
* @param {Number} numSides
*/
function ssdOffsetOf(sector, isSideUpper, numSides) {
const track = sector.trackNumber * numSides + (isSideUpper ? 1 : 0);
return track * SsdFormat.trackSize + sector.sectorNumber * SsdFormat.sectorSize;
}
/**
* SSD and DSD images hold sector contents and nothing else, so anything a DFS sector could not
* have held is lost. Copy protection usually shows up as one of these.
*
* @returns {string[]} what `disc` holds that an SSD or DSD cannot, worst first
* @param {Disc} disc
*/
export function ssdOrDsdShortfalls(disc) {
const counts = new Map();
for (let trackNum = 0; trackNum < disc.tracksUsed; ++trackNum) {
for (const upper of disc.isDoubleSided ? [false, true] : [false]) {
for (const sector of disc.getTrack(upper, trackNum).findSectors()) {
const shortfall = sectorShortfall(sector);
if (shortfall) counts.set(shortfall, (counts.get(shortfall) ?? 0) + 1);
}
}
}
return [...counts]
.sort(([, a], [, b]) => b - a)
.map(([shortfall, count]) => `${count} sector${count === 1 ? "" : "s"} ${shortfall}`);
}
/**
* @returns {Uint8Array}
* @param {Disc} disc
* @param {object} [options]
* @param {boolean} [options.force] save what fits instead of refusing a disc that will not fit
* @throws if the disc holds anything an SSD or DSD cannot, and `force` is not set
*/
export function toSsdOrDsd(disc, { force = false } = {}) {
if (!force) {
const shortfalls = ssdOrDsdShortfalls(disc);
if (shortfalls.length)
throw new Error(
`This disc cannot be saved as SSD or DSD: it has ${shortfalls.join(", ")}. ` +
`Save it as HFE to keep everything.`,
);
}
const numSides = disc.isDoubleSided ? 2 : 1;
const result = new Uint8Array(numSides * SsdFormat.tracksPerDisc * SsdFormat.trackSize);
let numTracks = 0;
for (let trackNum = 0; trackNum < disc.tracksUsed; ++trackNum) {
for (let side = 0; side < numSides; ++side) {
const trackObj = disc.getTrack(side === 1, trackNum);
for (const sector of trackObj.findSectors()) {
if (sectorShortfall(sector)) continue;
result.set(sector.sectorData, ssdOffsetOf(sector, side === 1, numSides));
numTracks = Math.max(numTracks, sector.trackNumber + 1);
}
}
}
return result.slice(0, numTracks * numSides * SsdFormat.trackSize);
}
export class Disc {
/**
* @returns {Disc} a new blank disc
*/
static createBlank() {
return new Disc(true, new DiscConfig());
}
/**
* @param {boolean} isWriteable
* @param {DiscConfig} config
* @param {string} name
*/
constructor(isWriteable, config, name) {
this.config = config;
this.name = name;
this.isDirty = false;
this.dirtySide = -1;
this.dirtyTrack = -1;
this.tracksUsed = 0;
this.isDoubleSided = false;
// Whether the surface holds a 48 tpi layout, which a drive reads by double stepping.
this.is40Track = false;
this._trackWriteListeners = new Set();
this._savingListeners = new Set();
this.isWriteable = isWriteable;
// Track which tracks have been written since the last snapshot.
// Keys are numeric: (track | (isSideUpper ? 0x100 : 0)).
this._snapshotDirtyTracks = new Set();
// Cumulative set of all tracks ever written since disc load (never cleared by snapshots).
// Same key encoding as _snapshotDirtyTracks.
this._everDirtyTracks = new Set();
// Cache of the previous snapshot's track data for structural sharing.
// Keys are "side:trackNum" strings, values are {pulses2Us, length} objects.
this._lastTrackSnapshots = Object.create(null);
// Original disc image data, stored for embedding in save-to-file snapshots
// and CRC32 verification on restore. _originalImageData is only set for
// local-file discs (not URL-sourced ones). _originalImageCrc32 is the CRC
// of the image bytes at load time — it is not updated if an onChange handler
// mutates the backing store. This is fine because the CRC is compared against
// the same source that would be reloaded (the original image or URL), not the
// mutated copy. If a mutable source URL were added in future, CRC verification
// should be skipped or the CRC updated accordingly.
this._originalImageData = null;
this._originalImageCrc32 = null;
this.initSurface(0);
}
/**
* @param {function(boolean, Number, Track): void} listener called once per flushed track
* @param {boolean} [savesChanges] whether the listener puts the image somewhere it is read back from
*/
addTrackWriteListener(listener, savesChanges = false) {
this._trackWriteListeners.add(listener);
if (savesChanges) this._savingListeners.add(listener);
}
get savesChanges() {
return this._savingListeners.size > 0;
}
/** @param {function(boolean, Number, Track): void} listener */
removeTrackWriteListener(listener) {
this._trackWriteListeners.delete(listener);
this._savingListeners.delete(listener);
}
/** @param {function(): void} listener called once, when a track is first written to this disc */
notifyOnFirstTrackWrite(listener) {
const onFirstWrite = () => {
this.removeTrackWriteListener(onFirstWrite);
listener();
};
this.addTrackWriteListener(onFirstWrite);
}
/**
* Record the CRC32 of the original disc image for verification on restore.
* Called by discFor() after loading. Does not retain the image bytes.
* @param {Uint8Array} data - the raw disc image bytes (used only to compute CRC32)
*/
setOriginalImageCrc32(data) {
this._originalImageCrc32 = crc32(data);
}
/**
* Store the original disc image bytes for embedding in snapshots.
* Only call this for local-file discs — URL-sourced discs should use
* setOriginalImageCrc32() instead to avoid retaining the full image.
* Computes CRC32 only if not already set (e.g. by discFor).
* @param {Uint8Array} data - the raw disc image bytes
*/
setOriginalImage(data) {
this._originalImageData = data;
if (this._originalImageCrc32 == null) {
this._originalImageCrc32 = crc32(data);
}
}
/** @returns {Uint8Array|null} the original disc image bytes, or null if not set */
get originalImageData() {
return this._originalImageData;
}
/** @returns {number|null} CRC32 of the original disc image, or null if not set */
get originalImageCrc32() {
return this._originalImageCrc32;
}
get writeProtected() {
return !this.isWriteable;
}
/**
* @param {boolean} isSideUpper
* @param {Number} trackNum
* @returns {Track} */
getTrack(isSideUpper, trackNum) {
return isSideUpper ? this.upperSide.tracks[trackNum] : this.lowerSide.tracks[trackNum];
}
buildTrack(isSideUpper, trackNum) {
this.setTrackUsed(isSideUpper, trackNum);
return new TrackBuilder(this.getTrack(isSideUpper, trackNum));
}
setTrackUsed(isSideUpper, trackNum) {
if (isSideUpper) this.isDoubleSided = true;
this.tracksUsed = Math.max(this.tracksUsed, trackNum + 1);
}
initSurface(initialByte) {
this.lowerSide = new Side(false, initialByte);
this.upperSide = new Side(true, initialByte);
this.tracksUsed = 0;
this.isDoubleSided = false;
}
readPulses(isSideUpper, track, position) {
return this.getTrack(isSideUpper, track).pulses2Us[position];
}
/**
* @param {boolean} isSideUpper
* @param {Number} track
* @param {Number} position
* @param {Number} pulses
*/
writePulses(isSideUpper, track, position, pulses) {
const trackObj = this.getTrack(isSideUpper, track);
Iif (position >= trackObj.length)
throw new Error(
`Attempt to write off end of track ${track}: position ${position} >= length ${trackObj.length}`,
);
Iif (this.isDirty) {
if (isSideUpper !== this.dirtySide || track !== this.dirtyTrack)
throw new Error("Switched dirty track or side");
}
this.isDirty = true;
this.dirtySide = isSideUpper;
this.dirtyTrack = track;
// Numeric key avoids string allocation on every pulse write.
// Upper bit encodes side, lower 8 bits encode track number.
const dirtyKey = track | (isSideUpper ? 0x100 : 0);
this._snapshotDirtyTracks.add(dirtyKey);
this._everDirtyTracks.add(dirtyKey);
trackObj.pulses2Us[position] = pulses;
}
/** @returns {?{isSideUpper: boolean, trackNum: Number}} the track written, if there was one */
flushWrites() {
if (!this.isDirty) {
Iif (this.dirtySide !== -1 || this.dirtyTrack !== -1) throw new Error("Bad state in disc dirty tracking");
return null;
}
const dirtySide = this.dirtySide;
const dirtyTrack = this.dirtyTrack;
this.isDirty = false;
this.dirtySide = -1;
this.dirtyTrack = -1;
const trackObj = this.getTrack(dirtySide, dirtyTrack);
this.setTrackUsed(dirtySide, dirtyTrack);
for (const listener of this._trackWriteListeners) listener(dirtySide, dirtyTrack, trackObj);
return { isSideUpper: dirtySide, trackNum: dirtyTrack };
}
/**
* Leave a track with no flux on it at all, as an erase head does.
*
* @param {boolean} isSideUpper
* @param {Number} trackNum
*/
eraseTrack(isSideUpper, trackNum) {
const trackObj = this.getTrack(isSideUpper, trackNum);
trackObj.pulses2Us.fill(0);
trackObj.length = IbmDiscFormat.bytesPerTrack;
const dirtyKey = trackNum | (isSideUpper ? 0x100 : 0);
this._snapshotDirtyTracks.add(dirtyKey);
this._everDirtyTracks.add(dirtyKey);
this.setTrackUsed(isSideUpper, trackNum);
for (const listener of this._trackWriteListeners) listener(isSideUpper, trackNum, trackObj);
}
/**
* Create a snapshot of all track data with structural sharing.
* Clean tracks reuse references from the previous snapshot;
* dirty tracks get fresh copies.
*/
snapshotState() {
const numSides = this.isDoubleSided ? 2 : 1;
// Use a plain object for JSON serialization compatibility.
// Keys are "side:trackNum" strings.
const tracks = Object.create(null);
for (let side = 0; side < numSides; ++side) {
for (let trackNum = 0; trackNum < this.tracksUsed; ++trackNum) {
const key = `${side === 1}:${trackNum}`;
const dirtyKey = trackNum | (side === 1 ? 0x100 : 0);
const trackObj = this.getTrack(side === 1, trackNum);
if (this._snapshotDirtyTracks.has(dirtyKey) || !this._lastTrackSnapshots[key]) {
// Dirty or first snapshot: copy the track data
tracks[key] = {
pulses2Us: trackObj.pulses2Us.slice(),
length: trackObj.length,
};
} else {
// Clean: reuse the previous snapshot's reference
tracks[key] = this._lastTrackSnapshots[key];
}
}
}
this._snapshotDirtyTracks.clear();
this._lastTrackSnapshots = tracks;
return {
tracksUsed: this.tracksUsed,
isDoubleSided: this.isDoubleSided,
isWriteable: this.isWriteable,
name: this.name,
tracks,
// Expose for save-to-file snapshots to identify dirty tracks.
// This is a Set and won't survive JSON serialization — it's only
// used by createSnapshot() before the snapshot is serialized.
_everDirtyTracks: new Set(this._everDirtyTracks),
_originalImageData: this._originalImageData,
_originalImageCrc32: this._originalImageCrc32,
};
}
/**
* Restore disc track data from a snapshot.
* For save-to-file snapshots, `state.tracks` is empty and `state.dirtyTracks`
* contains only the tracks modified since disc load. The base disc data must
* already be loaded before calling this method.
*/
restoreState(state) {
this.tracksUsed = state.tracksUsed;
this.isDoubleSided = state.isDoubleSided;
this.isWriteable = state.isWriteable;
this.name = state.name;
// Reset write-in-progress state
this.isDirty = false;
this.dirtySide = -1;
this.dirtyTrack = -1;
this._snapshotDirtyTracks.clear();
// Restore _everDirtyTracks from the snapshot if present (rewind path —
// the Set is carried in-memory but won't survive JSON serialization).
// For the save-to-file path, _everDirtyTracks is rebuilt from dirtyTracks below.
if (state._everDirtyTracks instanceof Set) {
this._everDirtyTracks = new Set(state._everDirtyTracks);
} else {
this._everDirtyTracks.clear();
}
// Restore full track data (rewind path — tracks contains all data)
this._lastTrackSnapshots = state.tracks;
for (const key of Object.keys(state.tracks)) {
const trackData = state.tracks[key];
const [sideStr, trackNumStr] = key.split(":");
const isSideUpper = sideStr === "true";
const trackNum = parseInt(trackNumStr, 10);
const trackObj = this.getTrack(isSideUpper, trackNum);
trackObj.pulses2Us.set(trackData.pulses2Us);
trackObj.length = trackData.length;
}
// Apply dirty track overlays (save-to-file path — base disc already loaded,
// overlay only the tracks that were written since disc load)
if (state.dirtyTracks) {
for (const key of Object.keys(state.dirtyTracks)) {
const trackData = state.dirtyTracks[key];
const [sideStr, trackNumStr] = key.split(":");
const isSideUpper = sideStr === "true";
const trackNum = parseInt(trackNumStr, 10);
const trackObj = this.getTrack(isSideUpper, trackNum);
trackObj.pulses2Us.set(trackData.pulses2Us);
trackObj.length = trackData.length;
this._everDirtyTracks.add(trackNum | (isSideUpper ? 0x100 : 0));
// A disc that keeps its changes at its source takes the overlay there too.
for (const listener of this._trackWriteListeners) listener(isSideUpper, trackNum, trackObj);
}
}
}
logSummary() {
const maxTrack = this.tracksUsed;
const numSides = this.isDoubleSided ? 2 : 1;
for (let side = 0; side < numSides; ++side) {
for (let trackNum = 0; trackNum < maxTrack; ++trackNum) {
const track = this.getTrack(side === 1, trackNum);
const sectors = track.findSectors();
if (sectors.length) {
if (track.length >= IbmDiscFormat.bytesPerTrack * 1.015) {
console.log(`Long track ${track.description}, ${track.length} bytes`);
} else if (track.length <= IbmDiscFormat.bytesPerTrack * 0.985) {
console.log(`Short track ${track.description}, ${track.length} bytes`);
}
if (sectors[0].isMfm) {
if (sectors.length !== 16 && sectors.length !== 18) {
console.log(`Non-standard MFM sector count ${track.description} count ${sectors.length}`);
}
} else {
if (sectors.length !== 10) {
console.log(`Non-standard FM sector count ${track.description} count ${sectors.length}`);
}
}
for (const sector of sectors) {
if (sector.hasHeaderCrcError) console.log(`${sector.description} has bad header crc`);
if (sector.trackNumber !== trackNum) console.log(`${sector.description} has bad track id`);
if (sector.hasDataCrcError) console.log(`${sector.description} has bad data crc`);
}
} else {
console.log(`"Unformatted track ${track.description}"`);
}
}
}
}
}
export class IbmDiscFormat {
static get bytesPerTrack() {
return 3125;
}
static get tracksPerDisc() {
return 84;
}
static get markClockPattern() {
return 0xc7;
}
static get idMarkDataPattern() {
return 0xfe;
}
static get dataMarkDataPattern() {
return 0xfb;
}
static get deletedDataMarkDataPattern() {
return 0xf8;
}
static get mfmA1Sync() {
return 0x4489;
}
static get mfmC2Sync() {
return 0x5224;
}
static get stdSync00s() {
return 6;
}
static get stdGap1FFs() {
return 16;
}
static get stdGap2FFs() {
return 11;
}
static get std10SectorGap3FFs() {
return 21;
}
/**
* @param {boolean} isMfm
* @returns {Number} initial CRC for type
*/
static crcInit(isMfm) {
// MFM starts with 3x 0xA1 sync bytes added.
return isMfm ? 0xcdb4 : 0xffff;
}
static crcAddByte(crc, byte) {
for (let i = 0; i < 8; ++i) {
const bit = byte & 0x80;
const bitTest = (crc & 0x8000) ^ (bit << 8);
crc = (crc << 1) & 0xffff;
if (bitTest) crc ^= 0x1021;
byte <<= 1;
}
return crc;
}
static crcAddBytes(crc, bytes) {
for (const byte of bytes) crc = IbmDiscFormat.crcAddByte(crc, byte);
return crc;
}
static fmTo2usPulses(clocks, data) {
let ret = 0;
for (let i = 0; i < 8; ++i) {
ret <<= 4;
if (clocks & 0x80) ret |= 0x08;
if (data & 0x80) ret |= 0x02;
clocks = (clocks << 1) & 0xff;
data = (data << 1) & 0xff;
}
// Bit 7's clock lands in bit 31, so back to unsigned.
return ret >>> 0;
}
static _2usPulsesToFm(pulses) {
let clocks = 0;
let data = 0;
let iffyPulses = false;
for (let i = 0; i < 8; ++i) {
clocks <<= 1;
data <<= 1;
if (pulses & 0x80000000) clocks |= 0x01;
if (pulses & 0x20000000) data |= 0x01;
// Any pulses off the 2us clock are suspicious FM data.
if (pulses & 0x50000000) iffyPulses = true;
pulses = (pulses << 4) & 0xffffffff;
}
return { clocks, data, iffyPulses };
}
static mfmTo2usPulses(lastBit, data) {
let pulses = 0;
for (let i = 0; i < 8; ++i) {
const bit = !!(data & 0x80);
pulses = (pulses << 2) & 0xffff;
data <<= 1;
if (bit) pulses |= 0x01;
else if (!lastBit) pulses |= 0x02;
lastBit = bit;
}
return { lastBit, pulses };
}
static _2usPulsesToMfm(pulses) {
let byte = 0;
for (let i = 0; i < 8; ++i) {
byte <<= 1;
if ((pulses & 0xc000) === 0x4000) byte |= 1;
pulses = (pulses << 2) & 0xffff;
}
return byte;
}
static checkPulse(pulseUs, isMfm) {
if (pulseUs < 3.5 || pulseUs > 8.5) return false;
if (isMfm && pulseUs > 5.5 && pulseUs < 6.5) return true;
return !(pulseUs > 4.5 && pulseUs < 7.5);
}
}
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