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1'use strict';2 3const { EMPTY_BUFFER } = require('./constants');4 5/**6 * Merges an array of buffers into a new buffer.7 *8 * @param {Buffer[]} list The array of buffers to concat9 * @param {Number} totalLength The total length of buffers in the list10 * @return {Buffer} The resulting buffer11 * @public12 */13function concat(list, totalLength) {14  if (list.length === 0) return EMPTY_BUFFER;15  if (list.length === 1) return list[0];16 17  const target = Buffer.allocUnsafe(totalLength);18  let offset = 0;19 20  for (let i = 0; i < list.length; i++) {21    const buf = list[i];22    target.set(buf, offset);23    offset += buf.length;24  }25 26  if (offset < totalLength) return target.slice(0, offset);27 28  return target;29}30 31/**32 * Masks a buffer using the given mask.33 *34 * @param {Buffer} source The buffer to mask35 * @param {Buffer} mask The mask to use36 * @param {Buffer} output The buffer where to store the result37 * @param {Number} offset The offset at which to start writing38 * @param {Number} length The number of bytes to mask.39 * @public40 */41function _mask(source, mask, output, offset, length) {42  for (let i = 0; i < length; i++) {43    output[offset + i] = source[i] ^ mask[i & 3];44  }45}46 47/**48 * Unmasks a buffer using the given mask.49 *50 * @param {Buffer} buffer The buffer to unmask51 * @param {Buffer} mask The mask to use52 * @public53 */54function _unmask(buffer, mask) {55  // Required until https://github.com/nodejs/node/issues/9006 is resolved.56  const length = buffer.length;57  for (let i = 0; i < length; i++) {58    buffer[i] ^= mask[i & 3];59  }60}61 62/**63 * Converts a buffer to an `ArrayBuffer`.64 *65 * @param {Buffer} buf The buffer to convert66 * @return {ArrayBuffer} Converted buffer67 * @public68 */69function toArrayBuffer(buf) {70  if (buf.byteLength === buf.buffer.byteLength) {71    return buf.buffer;72  }73 74  return buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength);75}76 77/**78 * Converts `data` to a `Buffer`.79 *80 * @param {*} data The data to convert81 * @return {Buffer} The buffer82 * @throws {TypeError}83 * @public84 */85function toBuffer(data) {86  toBuffer.readOnly = true;87 88  if (Buffer.isBuffer(data)) return data;89 90  let buf;91 92  if (data instanceof ArrayBuffer) {93    buf = Buffer.from(data);94  } else if (ArrayBuffer.isView(data)) {95    buf = Buffer.from(data.buffer, data.byteOffset, data.byteLength);96  } else {97    buf = Buffer.from(data);98    toBuffer.readOnly = false;99  }100 101  return buf;102}103 104try {105  const bufferUtil = require('bufferutil');106  const bu = bufferUtil.BufferUtil || bufferUtil;107 108  module.exports = {109    concat,110    mask(source, mask, output, offset, length) {111      if (length < 48) _mask(source, mask, output, offset, length);112      else bu.mask(source, mask, output, offset, length);113    },114    toArrayBuffer,115    toBuffer,116    unmask(buffer, mask) {117      if (buffer.length < 32) _unmask(buffer, mask);118      else bu.unmask(buffer, mask);119    }120  };121} catch (e) /* istanbul ignore next */ {122  module.exports = {123    concat,124    mask: _mask,125    toArrayBuffer,126    toBuffer,127    unmask: _unmask128  };129}130