<?php

/*
 * This file is part of SwiftMailer.
 * (c) 2004-2009 Chris Corbyn
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */


/**
 * Provides fixed-width byte sizes for reading fixed-width character sets.
 * @package Swift
 * @subpackage Encoder
 * @author Chris Corbyn
 * @author Xavier De Cock <xdecock@gmail.com>
 */
class Swift_CharacterReader_GenericFixedWidthReader
  implements Swift_CharacterReader
{
   
  /**
   * The number of bytes in a single character.
   * @var int
   * @access private
   */
  private $_width;
	
  /**
   * Creates a new GenericFixedWidthReader using $width bytes per character.
   * @param int $width
   */
  public function __construct($width)
  {
    $this->_width = $width;
  }

  /**
   * Returns the complete charactermap
   *
   * @param string $string
   * @param int $startOffset
   * @param array $currentMap
   * @param mixed $ignoredChars
   * @return $int
   */
  public function getCharPositions($string, $startOffset, &$currentMap, &$ignoredChars)
  {
  	$strlen = strlen($string);
  	// % and / are CPU intensive, so, maybe find a better way
  	$ignored = $strlen%$this->_width;
  	$ignoredChars = substr($string, - $ignored);
  	$currentMap = $this->_width;
  	return ($strlen - $ignored)/$this->_width;
  	
  }
  
  /**
   * Returns mapType
   * @int mapType
   */
  public function getMapType()
  {
  	return self::MAP_TYPE_FIXED_LEN;
  }

  /**
   * Returns an integer which specifies how many more bytes to read.
   * A positive integer indicates the number of more bytes to fetch before invoking
   * this method again.
   * A value of zero means this is already a valid character.
   * A value of -1 means this cannot possibly be a valid character.
   * @param string $bytes
   * @return int
   */
  public function validateByteSequence($bytes, $size)
  {
    $needed = $this->_width - $size;
    return ($needed > -1)
      ? $needed
      : -1
      ;
  }

  /**
   * Returns the number of bytes which should be read to start each character.
   * @return int
   */
  public function getInitialByteSize()
  {
    return $this->_width;
  }

}
