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-rw-r--r--midifile_cli.js313
1 files changed, 313 insertions, 0 deletions
diff --git a/midifile_cli.js b/midifile_cli.js
new file mode 100644
index 0000000..ee4a39e
--- /dev/null
+++ b/midifile_cli.js
@@ -0,0 +1,313 @@
+/* Wrapper for accessing strings through sequential reads */
+function Stream(str) {
+ var position = 0;
+
+ function read(length) {
+ var result = str.substr(position, length);
+ position += length;
+ return result;
+ }
+
+ /* read a big-endian 32-bit integer */
+ function readInt32() {
+ var result = (
+ (str.charCodeAt(position) << 24)
+ + (str.charCodeAt(position + 1) << 16)
+ + (str.charCodeAt(position + 2) << 8)
+ + str.charCodeAt(position + 3));
+ position += 4;
+ return result;
+ }
+
+ /* read a big-endian 16-bit integer */
+ function readInt16() {
+ var result = (
+ (str.charCodeAt(position) << 8)
+ + str.charCodeAt(position + 1));
+ position += 2;
+ return result;
+ }
+
+ /* read an 8-bit integer */
+ function readInt8(signed) {
+ var result = str.charCodeAt(position);
+ if (signed && result > 127) result -= 256;
+ position += 1;
+ return result;
+ }
+
+ function eof() {
+ return position >= str.length;
+ }
+
+ /* read a MIDI-style variable-length integer
+ (big-endian value in groups of 7 bits,
+ with top bit set to signify that another byte follows)
+ */
+ function readVarInt() {
+ var result = 0;
+ while (true) {
+ var b = readInt8();
+ if (b & 0x80) {
+ result += (b & 0x7f);
+ result <<= 7;
+ } else {
+ /* b is the last byte */
+ return result + b;
+ }
+ }
+ }
+
+ return {
+ 'eof': eof,
+ 'read': read,
+ 'readInt32': readInt32,
+ 'readInt16': readInt16,
+ 'readInt8': readInt8,
+ 'readVarInt': readVarInt
+ }
+}
+/*
+class to parse the .mid file format
+(depends on stream.js)
+*/
+function MidiFile(data) {
+ function readChunk(stream) {
+ var id = stream.read(4);
+ var length = stream.readInt32();
+ return {
+ 'id': id,
+ 'length': length,
+ 'data': stream.read(length)
+ };
+ }
+
+ var lastEventTypeByte;
+
+ function readEvent(stream) {
+ var event = {};
+ event.deltaTime = stream.readVarInt();
+ var eventTypeByte = stream.readInt8();
+ if ((eventTypeByte & 0xf0) == 0xf0) {
+ /* system / meta event */
+ if (eventTypeByte == 0xff) {
+ /* meta event */
+ event.type = 'meta';
+ var subtypeByte = stream.readInt8();
+ var length = stream.readVarInt();
+ switch(subtypeByte) {
+ case 0x00:
+ event.subtype = 'sequenceNumber';
+ if (length != 2) throw "Expected length for sequenceNumber event is 2, got " + length;
+ event.number = stream.readInt16();
+ return event;
+ case 0x01:
+ event.subtype = 'text';
+ event.text = stream.read(length);
+ return event;
+ case 0x02:
+ event.subtype = 'copyrightNotice';
+ event.text = stream.read(length);
+ return event;
+ case 0x03:
+ event.subtype = 'trackName';
+ event.text = stream.read(length);
+ return event;
+ case 0x04:
+ event.subtype = 'instrumentName';
+ event.text = stream.read(length);
+ return event;
+ case 0x05:
+ event.subtype = 'lyrics';
+ event.text = stream.read(length);
+ return event;
+ case 0x06:
+ event.subtype = 'marker';
+ event.text = stream.read(length);
+ return event;
+ case 0x07:
+ event.subtype = 'cuePoint';
+ event.text = stream.read(length);
+ return event;
+ case 0x20:
+ event.subtype = 'midiChannelPrefix';
+ if (length != 1) throw "Expected length for midiChannelPrefix event is 1, got " + length;
+ event.channel = stream.readInt8();
+ return event;
+ case 0x2f:
+ event.subtype = 'endOfTrack';
+ if (length != 0) throw "Expected length for endOfTrack event is 0, got " + length;
+ return event;
+ case 0x51:
+ event.subtype = 'setTempo';
+ if (length != 3) throw "Expected length for setTempo event is 3, got " + length;
+ event.microsecondsPerBeat = (
+ (stream.readInt8() << 16)
+ + (stream.readInt8() << 8)
+ + stream.readInt8()
+ )
+ return event;
+ case 0x54:
+ event.subtype = 'smpteOffset';
+ if (length != 5) throw "Expected length for smpteOffset event is 5, got " + length;
+ var hourByte = stream.readInt8();
+ event.frameRate = {
+ 0x00: 24, 0x20: 25, 0x40: 29, 0x60: 30
+ }[hourByte & 0x60];
+ event.hour = hourByte & 0x1f;
+ event.min = stream.readInt8();
+ event.sec = stream.readInt8();
+ event.frame = stream.readInt8();
+ event.subframe = stream.readInt8();
+ return event;
+ case 0x58:
+ event.subtype = 'timeSignature';
+ if (length != 4) throw "Expected length for timeSignature event is 4, got " + length;
+ event.numerator = stream.readInt8();
+ event.denominator = Math.pow(2, stream.readInt8());
+ event.metronome = stream.readInt8();
+ event.thirtyseconds = stream.readInt8();
+ return event;
+ case 0x59:
+ event.subtype = 'keySignature';
+ if (length != 2) throw "Expected length for keySignature event is 2, got " + length;
+ event.key = stream.readInt8(true);
+ event.scale = stream.readInt8();
+ return event;
+ case 0x7f:
+ event.subtype = 'sequencerSpecific';
+ event.data = stream.read(length);
+ return event;
+ default:
+ // console.log("Unrecognised meta event subtype: " + subtypeByte);
+ event.subtype = 'unknown'
+ event.data = stream.read(length);
+ return event;
+ }
+ event.data = stream.read(length);
+ return event;
+ } else if (eventTypeByte == 0xf0) {
+ event.type = 'sysEx';
+ var length = stream.readVarInt();
+ event.data = stream.read(length);
+ return event;
+ } else if (eventTypeByte == 0xf7) {
+ event.type = 'dividedSysEx';
+ var length = stream.readVarInt();
+ event.data = stream.read(length);
+ return event;
+ } else {
+ throw "Unrecognised MIDI event type byte: " + eventTypeByte;
+ }
+ } else {
+ /* channel event */
+ var param1;
+ if ((eventTypeByte & 0x80) == 0) {
+ /* running status - reuse lastEventTypeByte as the event type.
+ eventTypeByte is actually the first parameter
+ */
+ param1 = eventTypeByte;
+ eventTypeByte = lastEventTypeByte;
+ } else {
+ param1 = stream.readInt8();
+ lastEventTypeByte = eventTypeByte;
+ }
+ var eventType = eventTypeByte >> 4;
+ event.channel = eventTypeByte & 0x0f;
+ event.type = 'channel';
+ switch (eventType) {
+ case 0x08:
+ event.subtype = 'noteOff';
+ event.noteNumber = param1;
+ event.velocity = stream.readInt8();
+ return event;
+ case 0x09:
+ event.noteNumber = param1;
+ event.velocity = stream.readInt8();
+ if (event.velocity == 0) {
+ event.subtype = 'noteOff';
+ } else {
+ event.subtype = 'noteOn';
+ }
+ return event;
+ case 0x0a:
+ event.subtype = 'noteAftertouch';
+ event.noteNumber = param1;
+ event.amount = stream.readInt8();
+ return event;
+ case 0x0b:
+ event.subtype = 'controller';
+ event.controllerType = param1;
+ event.value = stream.readInt8();
+ return event;
+ case 0x0c:
+ event.subtype = 'programChange';
+ event.programNumber = param1;
+ return event;
+ case 0x0d:
+ event.subtype = 'channelAftertouch';
+ event.amount = param1;
+ return event;
+ case 0x0e:
+ event.subtype = 'pitchBend';
+ event.value = param1 + (stream.readInt8() << 7);
+ return event;
+ default:
+ throw "Unrecognised MIDI event type: " + eventType
+ /*
+ console.log("Unrecognised MIDI event type: " + eventType);
+ stream.readInt8();
+ event.subtype = 'unknown';
+ return event;
+ */
+ }
+ }
+ }
+
+ stream = Stream(data);
+ var headerChunk = readChunk(stream);
+ if (headerChunk.id != 'MThd' || headerChunk.length != 6) {
+ throw "Bad .mid file - header not found";
+ }
+ var headerStream = Stream(headerChunk.data);
+ var formatType = headerStream.readInt16();
+ var trackCount = headerStream.readInt16();
+ var timeDivision = headerStream.readInt16();
+
+ if (timeDivision & 0x8000) {
+ throw "Expressing time division in SMTPE frames is not supported yet"
+ } else {
+ ticksPerBeat = timeDivision;
+ }
+
+ var header = {
+ 'formatType': formatType,
+ 'trackCount': trackCount,
+ 'ticksPerBeat': ticksPerBeat
+ }
+ var tracks = [];
+ for (var i = 0; i < header.trackCount; i++) {
+ tracks[i] = [];
+ var trackChunk = readChunk(stream);
+ if (trackChunk.id != 'MTrk') {
+ throw "Unexpected chunk - expected MTrk, got "+ trackChunk.id;
+ }
+ var trackStream = Stream(trackChunk.data);
+ while (!trackStream.eof()) {
+ var event = readEvent(trackStream);
+ tracks[i].push(event);
+ //console.log(event);
+ }
+ }
+
+ return {
+ 'header': header,
+ 'tracks': tracks
+ }
+}
+
+
+module.exports = {
+ processMidiData : MidiFile
+
+}
generated by cgit v1.2.3-70-g09d2 (git 2.51.0) at 2025-12-10 15:49:22 +0000