rochars / riff-chunks

 * riff-chunks: Read and write the chunks of RIFF and RIFX files.

 * https://github.com/rochars/riff-chunks

 *

 * Copyright (c) 2017-2018 Rafael da Silva Rocha.

 *

 * Permission is hereby granted, free of charge, to any person obtaining

 * a copy of this software and associated documentation files (the

 * "Software"), to deal in the Software without restriction, including

 * without limitation the rights to use, copy, modify, merge, publish,

 * distribute, sublicense, and/or sell copies of the Software, and to

 * permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 *

 */

/**

 * @fileoverview The riff-chunks API.

 */

/** @module riffChunks */

import {unpackFrom, unpackString} from 'byte-data';

/** @private */

const uInt32_ = {'bits': 32};

/** @type {number} */

let head_ = 0;

/**

 * Return the chunks in a RIFF/RIFX file.

 * @param {!Uint8Array} buffer The file bytes.

 * @return {!Object} The RIFF chunks.

 */

    let chunkId = getChunkId_(buffer, 0);

    uInt32_['be'] = chunkId == 'RIFX';

    let format = unpackString(buffer, 8, 4);

    head_ += 4;

    return {

        'chunkId': chunkId,

        'chunkSize': getChunkSize_(buffer, 0),

        'format': format,

        'subChunks': getSubChunksIndex_(buffer)

    };

}

/**

 * Return the sub chunks of a RIFF file.

 * @param {!Uint8Array} buffer the RIFF file bytes.

 * @return {!Array<Object>} The subchunks of a RIFF/RIFX or LIST chunk.

 * @private

 */

function getSubChunksIndex_(buffer) {

    let chunks = [];

    let i = head_;

    while(i <= buffer.length - 8) {

        chunks.push(getSubChunkIndex_(buffer, i));

        i += 8 + chunks[chunks.length - 1]['chunkSize'];

        i = i % 2 ? i + 1 : i;

    }

    return chunks;

}

/**

 * Return a sub chunk from a RIFF file.

 * @param {!Uint8Array} buffer the RIFF file bytes.

 * @param {number} index The start index of the chunk.

 * @return {!Object} A subchunk of a RIFF/RIFX or LIST chunk.

 * @private

 */

function getSubChunkIndex_(buffer, index) {

    let chunk = {

        'chunkId': getChunkId_(buffer, index),

        'chunkSize': getChunkSize_(buffer, index),

    };

    if (chunk['chunkId'] == 'LIST') {

        chunk['format'] = unpackString(buffer, index + 8, 4);

        head_ += 4;

        chunk['subChunks'] = getSubChunksIndex_(buffer);

    } else {

        let realChunkSize = chunk['chunkSize'] % 2 ?

            chunk['chunkSize'] + 1 : chunk['chunkSize'];

        head_ = index + 8 + realChunkSize;

        chunk['chunkData'] = {

            'start': index + 8,

            'end': head_

        };

    }

    return chunk;

}

/**

 * Return the fourCC_ of a chunk.

 * @param {!Uint8Array} buffer the RIFF file bytes.

 * @param {number} index The start index of the chunk.

 * @return {string} The id of the chunk.

 * @private

 */

function getChunkId_(buffer, index) {

    head_ += 4;

    return unpackString(buffer, index, 4);

}

/**

 * Return the size of a chunk.

 * @param {!Uint8Array} buffer the RIFF file bytes.

 * @param {number} index The start index of the chunk.

 * @return {number} The size of the chunk without the id and size fields.

 * @private

 */

function getChunkSize_(buffer, index) {

    head_ += 4;

    return unpackFrom(buffer, uInt32_, index + 4);

}