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/* |
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* riff-chunks |
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* Read and write the chunks of RIFF and RIFX files. |
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* Copyright (c) 2017-2018 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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/** @private */ |
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const byteData = require("byte-data"); |
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/** @private */ |
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const uInt32_ = {"bits": 32}; |
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/** @private */ |
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const fourCC_ = {"bits": 32, "char": true}; |
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/** |
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* Write the bytes of a RIFF/RIFX file. |
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* @param {!Object} chunks A structure like the return of riffChunks.read(). |
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* @param {boolean} list An optional param indicating if the chunk is LIST. |
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* "LIST" chunks should not be rendered as Uint8Array. |
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* @return {!Array<number>|!Uint8Array} The bytes as Uint8Array when chunkId is |
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* "RIFF"/"RIFX" or as Array<number> when chunkId is "LIST". |
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*/ |
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function write(chunks, list=false) { |
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uInt32_["be"] = chunks["chunkId"] == "RIFX"; |
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let bytes = byteData.pack(chunks["chunkId"], fourCC_).concat( |
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byteData.pack(chunks["chunkSize"], uInt32_), |
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byteData.pack(chunks["format"], fourCC_), |
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writeSubChunks_(chunks["subChunks"])); |
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if (!list) { |
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bytes = new Uint8Array(bytes); |
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} |
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return bytes; |
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} |
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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} The chunk. |
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*/ |
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function read(buffer) { |
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buffer = [].slice.call(buffer); |
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let chunkId = getChunkId_(buffer, 0); |
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uInt32_["be"] = chunkId == "RIFX"; |
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return { |
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"chunkId": chunkId, |
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"chunkSize": getChunkSize_(buffer, 0), |
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"format": byteData.unpack(buffer.slice(8, 12), fourCC_), |
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"subChunks": getSubChunks_(buffer) |
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}; |
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} |
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/** |
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* Write the sub chunks of a RIFF file. |
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* @param {!Array<!Object>} chunks The chunks. |
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* @return {!Array<number>} The chunk bytes. |
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* @private |
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*/ |
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function writeSubChunks_(chunks) { |
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let subChunks = []; |
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let i = 0; |
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while (i < chunks.length) { |
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if (chunks[i]["chunkId"] == "LIST") { |
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subChunks = subChunks.concat(write(chunks[i], true)); |
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} else { |
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subChunks = subChunks.concat( |
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byteData.pack(chunks[i]["chunkId"], fourCC_), |
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byteData.pack(chunks[i]["chunkSize"], uInt32_), |
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chunks[i]["chunkData"]); |
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} |
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i++; |
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} |
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return subChunks; |
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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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* @return {!Array<Object>} The subchunks of a RIFF/RIFX or LIST chunk. |
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* @private |
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*/ |
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function getSubChunks_(buffer) { |
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let chunks = []; |
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let i = 12; |
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while(i <= buffer.length - 8) { |
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chunks.push(getSubChunk_(buffer, i)); |
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i += 8 + chunks[chunks.length - 1]["chunkSize"]; |
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i = i % 2 ? i + 1 : i; |
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} |
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return chunks; |
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} |
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/** |
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* Get a sub chunk from a RIFF file. |
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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 {!Object} A subchunk of a RIFF/RIFX or LIST chunk. |
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* @private |
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*/ |
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function getSubChunk_(buffer, index) { |
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let chunk = { |
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"chunkId": getChunkId_(buffer, index), |
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"chunkSize": getChunkSize_(buffer, index), |
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}; |
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if (chunk["chunkId"] == "LIST") { |
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chunk["format"] = byteData.unpack( |
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buffer.slice(index + 8, index + 12), fourCC_); |
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chunk["subChunks"] = getSubChunks_(buffer.slice(index)); |
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} else { |
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let slc = chunk["chunkSize"] % 2 ? chunk["chunkSize"] + 1 : chunk["chunkSize"]; |
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chunk["chunkData"] = buffer.slice( |
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index + 8, index + 8 + slc); |
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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} The id of the chunk. |
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* @private |
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*/ |
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function getChunkId_(buffer, index) { |
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return byteData.unpack(buffer.slice(index, index + 4), fourCC_); |
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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} The size of the chunk without the id and size fields. |
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* @private |
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*/ |
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function getChunkSize_(buffer, index) { |
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return byteData.unpack(buffer.slice(index + 4, index + 8), uInt32_); |
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} |
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module.exports.read = read; |
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module.exports.write = write; |
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rochars /
riff-chunks
