Samuel Kent
124 lines
2.6 KiB
JavaScript
124 lines
2.6 KiB
JavaScript
var utils = require('./utils');
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function checkMagicId3(view, offset) {
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var id3Magic = utils.readBytes(view, offset, 3);
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//"ID3"
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return id3Magic[0] === 73 && id3Magic[1] === 68 && id3Magic[2] === 51;
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}
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function getUint28(view, offset) {
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var sizeBytes = utils.readBytes(view, offset, 4);
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var mask = 0xfffffff;
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return ((sizeBytes[0] & mask) << 21) |
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((sizeBytes[1] & mask) << 14) |
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((sizeBytes[2] & mask) << 7) |
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(sizeBytes[3] & mask);
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}
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//http://id3.org/id3v2.3.0
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//http://id3.org/id3v2.4.0-structure
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//http://id3.org/id3v2.4.0-frames
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module.exports = function(buffer) {
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var view = utils.createView(buffer);
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if (!checkMagicId3(view, 0)) {
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return null;
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}
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var offset = 3;
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//var majorVersion = view.getUint8(offset);
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offset += 2;
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var flags = view.getUint8(offset);
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offset++;
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var size = getUint28(view, offset);
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offset += 4;
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var extendedHeader = (flags & 128) > 0;
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if (extendedHeader) {
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offset += getUint28(view, offset);
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}
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function readFrame(offset) {
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try {
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var id = utils.readAscii(view, offset, 4);
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var size = getUint28(view, offset + 4);
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offset += 10; //+2 more for flags we don't care about
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if (id[0] !== 'T') {
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return {
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id: id,
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size: size + 10
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};
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}
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var encoding = view.getUint8(offset),
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data = '';
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if (encoding <= 3) {
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offset++;
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if (encoding === 3) {
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//UTF8 - null terminated
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data = utils.readUtf8(view, offset, size - 1);
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} else {
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//ISO-8859-1, UTF-16, UTF-16BE
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//UTF-16 and UTF-16BE are $FF $00 terminated
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//ISO is null terminated
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//screw these encodings, read it as ascii
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data = utils.readAscii(view, offset, size - 1);
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}
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} else {
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//no encoding info, read it as ascii
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data = utils.readAscii(view, offset, size);
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}
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//id3v2.4 is supposed to have encoding terminations, but sometimes
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//they don't? meh.
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data = utils.trimNull(data);
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return {
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id: id,
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size: size + 10,
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content: data
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};
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} catch (e) {
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return null;
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}
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}
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var idMap = {
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TALB: 'album',
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TCOM: 'composer',
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TIT1: 'title',
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TIT2: 'title',
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TPE1: 'artist',
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TRCK: 'track',
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TSSE: 'encoder',
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TDRC: 'year',
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TCON: 'genre'
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};
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var endOfTags = offset + size,
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frames = {};
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while (offset < endOfTags) {
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var frame = readFrame(offset);
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if (!frame) {
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break;
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}
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offset += frame.size;
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if (!frame.content) {
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continue;
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}
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var id = idMap[frame.id] || frame.id;
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if (id === 'TXXX') {
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var nullByte = frame.content.indexOf('\u0000');
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id = frame.content.substring(0, nullByte);
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frames[id] = frame.content.substring(nullByte + 1);
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} else {
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frames[id] = frames[frame.id] = frame.content;
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}
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}
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return frames;
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}; |