snappyjs/index.js

JavaScript implementation of Google's Snappy compression library

// The MIT License (MIT)
//
// Copyright (c) 2016 Zhipeng Jia
//
// 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.

'use strict'

function isNode () {
  if (typeof process === 'object') {
    if (typeof process.versions === 'object') {
      if (typeof process.versions.node !== 'undefined') {
        return true
      }
    }
  }
  return false
}

function isUint8Array (object) {
  return object instanceof Uint8Array && (!isNode() || !Buffer.isBuffer(object))
}

function isArrayBuffer (object) {
  return object instanceof ArrayBuffer
}

function isBuffer (object) {
  if (!isNode()) {
    return false
  }
  return Buffer.isBuffer(object)
}

var SnappyDecompressor = require('./snappy_decompressor').SnappyDecompressor
var SnappyCompressor = require('./snappy_compressor').SnappyCompressor

var TYPE_ERROR_MSG = 'Argument compressed must be type of ArrayBuffer, Buffer, or Uint8Array'

function uncompress (compressed, maxLength) {
  if (!isUint8Array(compressed) && !isArrayBuffer(compressed) && !isBuffer(compressed)) {
    throw new TypeError(TYPE_ERROR_MSG)
  }
  var uint8Mode = false
  var arrayBufferMode = false
  if (isUint8Array(compressed)) {
    uint8Mode = true
  } else if (isArrayBuffer(compressed)) {
    arrayBufferMode = true
    compressed = new Uint8Array(compressed)
  }
  var decompressor = new SnappyDecompressor(compressed)
  var length = decompressor.readUncompressedLength()
  if (length === -1) {
    throw new Error('Invalid Snappy bitstream')
  }
  if (length > maxLength) {
    throw new Error(`The uncompressed length of ${length} is too big, expect at most ${maxLength}`)
  }
  var uncompressed, uncompressedView
  if (uint8Mode) {
    uncompressed = new Uint8Array(length)
    if (!decompressor.uncompressToBuffer(uncompressed)) {
      throw new Error('Invalid Snappy bitstream')
    }
  } else if (arrayBufferMode) {
    uncompressed = new ArrayBuffer(length)
    uncompressedView = new Uint8Array(uncompressed)
    if (!decompressor.uncompressToBuffer(uncompressedView)) {
      throw new Error('Invalid Snappy bitstream')
    }
  } else {
    uncompressed = Buffer.alloc(length)
    if (!decompressor.uncompressToBuffer(uncompressed)) {
      throw new Error('Invalid Snappy bitstream')
    }
  }
  return uncompressed
}

function compress (uncompressed) {
  if (!isUint8Array(uncompressed) && !isArrayBuffer(uncompressed) && !isBuffer(uncompressed)) {
    throw new TypeError(TYPE_ERROR_MSG)
  }
  var uint8Mode = false
  var arrayBufferMode = false
  if (isUint8Array(uncompressed)) {
    uint8Mode = true
  } else if (isArrayBuffer(uncompressed)) {
    arrayBufferMode = true
    uncompressed = new Uint8Array(uncompressed)
  }
  var compressor = new SnappyCompressor(uncompressed)
  var maxLength = compressor.maxCompressedLength()
  var compressed, compressedView
  var length
  if (uint8Mode) {
    compressed = new Uint8Array(maxLength)
    length = compressor.compressToBuffer(compressed)
  } else if (arrayBufferMode) {
    compressed = new ArrayBuffer(maxLength)
    compressedView = new Uint8Array(compressed)
    length = compressor.compressToBuffer(compressedView)
  } else {
    compressed = Buffer.alloc(maxLength)
    length = compressor.compressToBuffer(compressed)
  }
  if (!compressed.slice) { // ie11
    var compressedArray = new Uint8Array(Array.prototype.slice.call(compressed, 0, length))
    if (uint8Mode) {
      return compressedArray
    } else if (arrayBufferMode) {
      return compressedArray.buffer
    } else {
      throw new Error('Not implemented')
    }
  }

  return compressed.slice(0, length)
}

exports.uncompress = uncompress
exports.compress = compress