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/*! |
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* riff-chunks |
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* Get the chunks of RIFF and RIFX files. |
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* Copyright (c) 2017 Rafael da Silva Rocha. |
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* https://github.com/rochars/riff-chunks |
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* |
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*/ |
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const byteData = require("byte-data"); |
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/** |
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* Get the chunks of a RIFF/RIFX file. |
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* @param {Uint8Array|!Array<number>} buffer The file bytes. |
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* @return {Object} |
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*/ |
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function riffChunks(buffer) { |
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let chunkId = getChunkId(buffer, 0); |
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let bigEndian = chunkId == "RIFX"; |
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return { |
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"chunkId": chunkId, |
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"chunkSize": getChunkSize(buffer, 0, bigEndian), |
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"format": byteData.fromBytes(buffer.slice(8, 12), 8, byteData.str), |
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"subChunks": getSubChunks(buffer, bigEndian) |
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}; |
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} |
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/** |
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* Get the sub chunks of a RIFF file. |
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* @param {Uint8Array|!Array<number>} buffer the RIFF file bytes. |
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* @param {boolean} bigEndian true if its RIFX. |
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* @return {Object} |
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*/ |
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function getSubChunks(buffer, bigEndian) { |
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let chunks = []; |
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let i = 12; |
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while(i < buffer.length) { |
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chunks.push(getSubChunk(buffer, i, bigEndian)); |
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i += 8 + chunks[chunks.length - 1].subChunkSize; |
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} |
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return chunks; |
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} |
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function getSubChunk(buffer, index, bigEndian) { |
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let chunk = { |
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"subChunkId": getChunkId(buffer, index), |
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"subChunkSize": getChunkSize(buffer, index, bigEndian) |
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}; |
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if (chunk.subChunkId == "LIST") { |
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chunk.subChunks = getSubChunks( |
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buffer.slice(index, index + chunk.subChunkSize), bigEndian); |
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} else { |
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chunk.subChunkData = buffer.slice( |
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index + 8, index + 8 + chunk.subChunkSize); |
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} |
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return chunk; |
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} |
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/** |
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* Return the FourCC of a chunk. |
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* @param {Uint8Array|!Array<number>} buffer the RIFF file bytes. |
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* @param {number} index The start index of the chunk. |
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* @return {string} |
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*/ |
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function getChunkId(buffer, index) { |
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return byteData.fromBytes( |
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buffer.slice(index, index + 4), 8, byteData.str); |
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} |
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/** |
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* Return the size of a chunk. |
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* @param {Uint8Array|!Array<number>} buffer the RIFF file bytes. |
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* @param {number} index The start index of the chunk. |
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* @return {number} |
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*/ |
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function getChunkSize(buffer, index, bigEndian) { |
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return byteData.fromBytes( |
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buffer.slice(index + 4, index + 8), |
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32, |
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{'be': bigEndian, "single": true}); |
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} |
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module.exports = riffChunks; |
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rochars /
riff-chunks
