base64.coffee

#
#Copyright (c) 2008 Fred Palmer fred.palmer_at_gmail.com
#
#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.
#
StringBuffer = ->
  @buffer = []
  return
Utf8EncodeEnumerator = (input) ->
  @_input = input
  @_index = -1
  @_buffer = []
  return

# "\r\n" -> "\n"
#
Base64DecodeEnumerator = (input) ->
  @_input = input
  @_index = -1
  @_buffer = []
  return
StringBuffer::append = append = (string) ->
  @buffer.push string
  this

StringBuffer::toString = toString = ->
  @buffer.join ""

Base64 =
  codex: "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
  encode: (input) ->
    output = new StringBuffer()
    enumerator = new Utf8EncodeEnumerator(input)
    while enumerator.moveNext()
      chr1 = enumerator.current
      enumerator.moveNext()
      chr2 = enumerator.current
      enumerator.moveNext()
      chr3 = enumerator.current
      enc1 = chr1 >> 2
      enc2 = ((chr1 & 3) << 4) | (chr2 >> 4)
      enc3 = ((chr2 & 15) << 2) | (chr3 >> 6)
      enc4 = chr3 & 63
      if isNaN(chr2)
        enc3 = enc4 = 64
      else enc4 = 64  if isNaN(chr3)
      output.append @codex.charAt(enc1) + @codex.charAt(enc2) + @codex.charAt(enc3) + @codex.charAt(enc4)
    output.toString()

  decode: (input) ->
    output = new StringBuffer()
    enumerator = new Base64DecodeEnumerator(input)
    while enumerator.moveNext()
      charCode = enumerator.current
      if charCode < 128
        output.append String.fromCharCode(charCode)
      else if (charCode > 191) and (charCode < 224)
        enumerator.moveNext()
        charCode2 = enumerator.current
        output.append String.fromCharCode(((charCode & 31) << 6) | (charCode2 & 63))
      else
        enumerator.moveNext()
        charCode2 = enumerator.current
        enumerator.moveNext()
        charCode3 = enumerator.current
        output.append String.fromCharCode(((charCode & 15) << 12) | ((charCode2 & 63) << 6) | (charCode3 & 63))
    output.toString()

Utf8EncodeEnumerator:: =
  current: Number.NaN
  moveNext: ->
    if @_buffer.length > 0
      @current = @_buffer.shift()
      true
    else if @_index >= (@_input.length - 1)
      @current = Number.NaN
      false
    else
      charCode = @_input.charCodeAt(++@_index)
      if (charCode is 13) and (@_input.charCodeAt(@_index + 1) is 10)
        charCode = 10
        @_index += 2
      if charCode < 128
        @current = charCode
      else if (charCode > 127) and (charCode < 2048)
        @current = (charCode >> 6) | 192
        @_buffer.push (charCode & 63) | 128
      else
        @current = (charCode >> 12) | 224
        @_buffer.push ((charCode >> 6) & 63) | 128
        @_buffer.push (charCode & 63) | 128
      true

Base64DecodeEnumerator:: =
  current: 64
  moveNext: ->
    if @_buffer.length > 0
      @current = @_buffer.shift()
      true
    else if @_index >= (@_input.length - 1)
      @current = 64
      false
    else
      enc1 = Base64.codex.indexOf(@_input.charAt(++@_index))
      enc2 = Base64.codex.indexOf(@_input.charAt(++@_index))
      enc3 = Base64.codex.indexOf(@_input.charAt(++@_index))
      enc4 = Base64.codex.indexOf(@_input.charAt(++@_index))
      chr1 = (enc1 << 2) | (enc2 >> 4)
      chr2 = ((enc2 & 15) << 4) | (enc3 >> 2)
      chr3 = ((enc3 & 3) << 6) | enc4
      @current = chr1
      @_buffer.push chr2  unless enc3 is 64
      @_buffer.push chr3  unless enc4 is 64
      true