253 lines
8.4 KiB
JavaScript
253 lines
8.4 KiB
JavaScript
/**
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* mux.js
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*
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* Copyright (c) Brightcove
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* Licensed Apache-2.0 https://github.com/videojs/mux.js/blob/master/LICENSE
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*
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* Tools for parsing ID3 frame data
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* @see http://id3.org/id3v2.3.0
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*/
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'use strict';
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var
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typedArrayIndexOf = require('../utils/typed-array').typedArrayIndexOf,
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// Frames that allow different types of text encoding contain a text
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// encoding description byte [ID3v2.4.0 section 4.]
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textEncodingDescriptionByte = {
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Iso88591: 0x00, // ISO-8859-1, terminated with \0.
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Utf16: 0x01, // UTF-16 encoded Unicode BOM, terminated with \0\0
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Utf16be: 0x02, // UTF-16BE encoded Unicode, without BOM, terminated with \0\0
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Utf8: 0x03 // UTF-8 encoded Unicode, terminated with \0
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},
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// return a percent-encoded representation of the specified byte range
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// @see http://en.wikipedia.org/wiki/Percent-encoding
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percentEncode = function(bytes, start, end) {
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var i, result = '';
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for (i = start; i < end; i++) {
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result += '%' + ('00' + bytes[i].toString(16)).slice(-2);
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}
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return result;
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},
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// return the string representation of the specified byte range,
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// interpreted as UTf-8.
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parseUtf8 = function(bytes, start, end) {
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return decodeURIComponent(percentEncode(bytes, start, end));
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},
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// return the string representation of the specified byte range,
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// interpreted as ISO-8859-1.
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parseIso88591 = function(bytes, start, end) {
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return unescape(percentEncode(bytes, start, end)); // jshint ignore:line
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},
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parseSyncSafeInteger = function(data) {
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return (data[0] << 21) |
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(data[1] << 14) |
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(data[2] << 7) |
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(data[3]);
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},
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frameParsers = {
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'APIC': function(frame) {
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var
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i = 1,
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mimeTypeEndIndex,
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descriptionEndIndex,
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LINK_MIME_TYPE = '-->';
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if (frame.data[0] !== textEncodingDescriptionByte.Utf8) {
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// ignore frames with unrecognized character encodings
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return;
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}
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// parsing fields [ID3v2.4.0 section 4.14.]
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mimeTypeEndIndex = typedArrayIndexOf(frame.data, 0, i);
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if (mimeTypeEndIndex < 0) {
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// malformed frame
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return;
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}
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// parsing Mime type field (terminated with \0)
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frame.mimeType = parseIso88591(frame.data, i, mimeTypeEndIndex);
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i = mimeTypeEndIndex + 1;
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// parsing 1-byte Picture Type field
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frame.pictureType = frame.data[i];
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i++
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descriptionEndIndex = typedArrayIndexOf(frame.data, 0, i);
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if (descriptionEndIndex < 0) {
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// malformed frame
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return;
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}
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// parsing Description field (terminated with \0)
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frame.description = parseUtf8(frame.data, i, descriptionEndIndex);
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i = descriptionEndIndex + 1;
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if (frame.mimeType === LINK_MIME_TYPE) {
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// parsing Picture Data field as URL (always represented as ISO-8859-1 [ID3v2.4.0 section 4.])
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frame.url = parseIso88591(frame.data, i, frame.data.length)
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} else {
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// parsing Picture Data field as binary data
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frame.pictureData = frame.data.subarray(i, frame.data.length);
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}
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},
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'T*': function(frame) {
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if (frame.data[0] !== textEncodingDescriptionByte.Utf8) {
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// ignore frames with unrecognized character encodings
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return;
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}
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// parse text field, do not include null terminator in the frame value
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// frames that allow different types of encoding contain terminated text [ID3v2.4.0 section 4.]
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frame.value = parseUtf8(frame.data, 1, frame.data.length).replace(/\0*$/, '');
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// text information frames supports multiple strings, stored as a terminator separated list [ID3v2.4.0 section 4.2.]
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frame.values = frame.value.split('\0');
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},
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'TXXX': function(frame) {
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var descriptionEndIndex;
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if (frame.data[0] !== textEncodingDescriptionByte.Utf8) {
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// ignore frames with unrecognized character encodings
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return;
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}
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descriptionEndIndex = typedArrayIndexOf(frame.data, 0, 1);
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if (descriptionEndIndex === -1) {
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return;
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}
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// parse the text fields
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frame.description = parseUtf8(frame.data, 1, descriptionEndIndex);
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// do not include the null terminator in the tag value
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// frames that allow different types of encoding contain terminated text
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// [ID3v2.4.0 section 4.]
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frame.value = parseUtf8(
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frame.data,
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descriptionEndIndex + 1,
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frame.data.length
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).replace(/\0*$/, '');
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frame.data = frame.value;
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},
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'W*': function(frame) {
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// parse URL field; URL fields are always represented as ISO-8859-1 [ID3v2.4.0 section 4.]
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// if the value is followed by a string termination all the following information should be ignored [ID3v2.4.0 section 4.3]
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frame.url = parseIso88591(frame.data, 0, frame.data.length).replace(/\0.*$/, '');
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},
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'WXXX': function(frame) {
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var descriptionEndIndex;
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if (frame.data[0] !== textEncodingDescriptionByte.Utf8) {
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// ignore frames with unrecognized character encodings
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return;
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}
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descriptionEndIndex = typedArrayIndexOf(frame.data, 0, 1);
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if (descriptionEndIndex === -1) {
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return;
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}
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// parse the description and URL fields
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frame.description = parseUtf8(frame.data, 1, descriptionEndIndex);
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// URL fields are always represented as ISO-8859-1 [ID3v2.4.0 section 4.]
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// if the value is followed by a string termination all the following information
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// should be ignored [ID3v2.4.0 section 4.3]
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frame.url = parseIso88591(
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frame.data,
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descriptionEndIndex + 1,
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frame.data.length
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).replace(/\0.*$/, '');
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},
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'PRIV': function(frame) {
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var i;
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for (i = 0; i < frame.data.length; i++) {
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if (frame.data[i] === 0) {
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// parse the description and URL fields
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frame.owner = parseIso88591(frame.data, 0, i);
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break;
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}
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}
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frame.privateData = frame.data.subarray(i + 1);
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frame.data = frame.privateData;
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}
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};
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var parseId3Frames = function(data) {
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var frameSize, frameHeader,
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frameStart = 10,
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tagSize = 0,
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frames = [];
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// If we don't have enough data for a header, 10 bytes,
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// or 'ID3' in the first 3 bytes this is not a valid ID3 tag.
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if (data.length < 10 ||
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data[0] !== 'I'.charCodeAt(0) ||
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data[1] !== 'D'.charCodeAt(0) ||
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data[2] !== '3'.charCodeAt(0)) {
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return;
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}
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// the frame size is transmitted as a 28-bit integer in the
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// last four bytes of the ID3 header.
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// The most significant bit of each byte is dropped and the
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// results concatenated to recover the actual value.
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tagSize = parseSyncSafeInteger(data.subarray(6, 10));
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// ID3 reports the tag size excluding the header but it's more
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// convenient for our comparisons to include it
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tagSize += 10;
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// check bit 6 of byte 5 for the extended header flag.
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var hasExtendedHeader = data[5] & 0x40;
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if (hasExtendedHeader) {
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// advance the frame start past the extended header
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frameStart += 4; // header size field
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frameStart += parseSyncSafeInteger(data.subarray(10, 14));
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tagSize -= parseSyncSafeInteger(data.subarray(16, 20)); // clip any padding off the end
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}
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// parse one or more ID3 frames
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// http://id3.org/id3v2.3.0#ID3v2_frame_overview
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do {
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// determine the number of bytes in this frame
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frameSize = parseSyncSafeInteger(data.subarray(frameStart + 4, frameStart + 8));
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if (frameSize < 1) {
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break;
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}
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frameHeader = String.fromCharCode(data[frameStart],
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data[frameStart + 1],
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data[frameStart + 2],
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data[frameStart + 3]);
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var frame = {
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id: frameHeader,
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data: data.subarray(frameStart + 10, frameStart + frameSize + 10)
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};
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frame.key = frame.id;
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// parse frame values
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if (frameParsers[frame.id]) {
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// use frame specific parser
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frameParsers[frame.id](frame);
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} else if (frame.id[0] === 'T') {
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// use text frame generic parser
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frameParsers['T*'](frame);
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} else if (frame.id[0] === 'W') {
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// use URL link frame generic parser
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frameParsers['W*'](frame);
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}
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frames.push(frame);
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frameStart += 10; // advance past the frame header
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frameStart += frameSize; // advance past the frame body
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} while (frameStart < tagSize);
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return frames;
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}
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module.exports = {
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parseId3Frames: parseId3Frames,
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parseSyncSafeInteger: parseSyncSafeInteger,
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frameParsers: frameParsers,
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};
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