probe-image-size/lib/common.js

Get image size without full download (JPG, GIF, PNG, WebP, BMP, TIFF, PSD)

'use strict'


var Transform = require('stream').Transform
var streamParser = require('stream-parser')


function ParserStream () {
  Transform.call(this, { readableObjectMode: true })
}

// Inherit from Transform
ParserStream.prototype = Object.create(Transform.prototype)
ParserStream.prototype.constructor = ParserStream

streamParser(ParserStream.prototype)


exports.ParserStream = ParserStream


exports.sliceEq = function (src, start, dest) {
  for (var i = start, j = 0; j < dest.length;) {
    if (src[i++] !== dest[j++]) return false
  }
  return true
}

exports.str2arr = function (str, format) {
  var arr = []
  var i = 0

  if (format && format === 'hex') {
    while (i < str.length) {
      arr.push(parseInt(str.slice(i, i + 2), 16))
      i += 2
    }
  } else {
    for (; i < str.length; i++) {
      arr.push(str.charCodeAt(i) & 0xFF)
    }
  }

  return arr
}

exports.readUInt16LE = function (data, offset) {
  return data[offset] | (data[offset + 1] << 8)
}

exports.readUInt16BE = function (data, offset) {
  return (data[offset] << 8) | data[offset + 1]
}

exports.readInt16LE = function (data, offset) {
  return (exports.readUInt16LE(data, offset) << 16) >> 16
}

exports.readInt16BE = function (data, offset) {
  return (exports.readUInt16BE(data, offset) << 16) >> 16
}

exports.readUInt32LE = function (data, offset) {
  return (data[offset] |
    (data[offset + 1] << 8) |
    (data[offset + 2] << 16)) +
    data[offset + 3] * 0x1000000
}

exports.readUInt32BE = function (data, offset) {
  return data[offset] * 0x1000000 +
    ((data[offset + 1] << 16) |
    (data[offset + 2] << 8) |
    data[offset + 3])
}

exports.readInt32LE = function (data, offset) {
  return exports.readUInt32LE(data, offset) | 0
}

exports.readInt32BE = function (data, offset) {
  return exports.readUInt32BE(data, offset) | 0
}


function ProbeError (message, code, statusCode) {
  Error.call(this)

  // Include stack trace in error object
  if (Error.captureStackTrace) {
    // Chrome and NodeJS
    Error.captureStackTrace(this, this.constructor)
  } else {
    // FF, IE 10+ and Safari 6+. Fallback for others
    this.stack = (new Error()).stack || ''
  }

  this.name = this.constructor.name

  this.message = message
  if (code) this.code = code
  if (statusCode) this.statusCode = statusCode
}

// Inherit from Error
ProbeError.prototype = Object.create(Error.prototype)
ProbeError.prototype.constructor = ProbeError


exports.ProbeError = ProbeError