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<?php
/**
* File containing the ezcArchiveChecksums class.
*
* @package Archive
* @version 1.4.1
* @copyright Copyright (C) 2005-2010 eZ Systems AS. All rights reserved.
* @license http://ez.no/licenses/new_bsd New BSD License
* @access private
*/
/**
* The ezcArchiveChecksums is a collection of checksum algorithms. The
* total-byte-value checksum and CRC32 checksum are currently available.
*
* For each different checksum are two methods available:
* - Calculate the checksum from a string.
* - Calculate the checksum from a file.
*
* The latter will consume less memory since a part of the file is read in
* memory at the time, and will be freed after use. The consequence might be
* that the checksum from a string is a bit faster.
*
* @package Archive
* @version 1.4.1
* @access private
*/
class ezcArchiveChecksums
{
/**
* The CRC-32 lookup table.
*
* @var array(int)
*/
private static $crc32Table = false;
/**
* Calculates the total-byte-value checksum from a string.
*
* Returns the total ASCII value from all characters in the data string.
* Example 1: For example:
*
* <code>
* $crc = ezcArchiveChecksums::getTotalByteValueFromFile( "abc" );
* // $crc contains the value: 141 + 142 + 143 = 426
* </code>
*
* @param string $data Character string.
* @return int The total byte value.
*
* @see getTotalByteValueFromFile()
*/
public static function getTotalByteValueFromString( $data )
{
$total = 0;
$length = strlen( $data );
for ( $i = 0; $i < $length; $i++ )
{
$total += ord( $data[$i] );
}
return $total;
}
/**
* Calculates the total-byte-value checksum from a file.
*
* Returns the total ASCII value from all characters in the data string.
* For example:
*
* <code>
* $crc = ezcArchiveChecksums::getTotalByteValueFromFile( "abc" );
* // $crc contains the value: 141 + 142 + 143 = 426
* </code>
*
* @param string $fileName The file to use
* @return int Value which contains the total byte value.
*/
public static function getTotalByteValueFromFile( $fileName )
{
if ( ( $fp = fopen( $fileName, 'rb' ) ) === false )
{
return false;
}
// Perform the algorithm on each character in file
$total = 0;
while ( true )
{
$i = fread( $fp, 1 );
if ( strlen( $i ) == 0 )
{
break;
}
$total += ord( $i );
}
fclose( $fp );
return $total;
}
/**
* Calculates the (official) CRC-32 polynomial from a $data string as input.
*
* @param string $data
* @return int The calculated CRC-32.
*/
public static function getCrc32FromString( $data )
{
return crc32( $data );
}
/**
* Calculates the (official) CRC-32 polynomial from a file.
*
* This method is taken from the PHP user comments
* (http://no.php.net/manual/en/function.crc32.php).
*
* @param string $fileName Absolute or relative path to the file.
* @return int The calculated CRC-32.
*/
public static function getCrc32FromFile( $fileName )
{
if ( self::$crc32Table === false )
{
self::crc32InitTable();
}
// Once the lookup table has been filled in by the two functions above,
// this function creates all CRCs using only the lookup table.
// You need unsigned variables because negative values
// introduce high bits where zero bits are required.
// PHP doesn't have unsigned integers:
// I've solved this problem by doing a '&' after a '>>'.
// Start out with all bits set high.
$crc = 0xffffffff;
// Added for issue #13517: Not possible to add directories to an archive on Windows
if ( is_dir( $fileName ) )
{
return false;
}
if ( ( $fp = fopen( $fileName ,'rb' ) ) === false )
{
return false;
}
// Perform the algorithm on each character in file
while ( true )
{
$i = fread( $fp, 1 );
if ( strlen( $i ) == 0 )
{
break;
}
$crc = ( ( $crc >> 8 ) & 0x00ffffff ) ^ self::$crc32Table[( $crc & 0xFF ) ^ ord( $i )];
}
fclose( $fp );
// Exclusive OR the result with the beginning value.
return $crc ^ 0xffffffff;
}
/**
* Initializes the CRC-32 table.
*
* Builds the lookup table array. This is the official polynomial used by
* CRC-32 in PKZip, WinZip and Ethernet.
*
* This method is taken from the PHP user comments
* (http://no.php.net/manual/en/function.crc32.php).
*/
protected static function crc32InitTable()
{
// Builds lookup table array
// This is the official polynomial used by
// CRC-32 in PKZip, WinZip and Ethernet.
$polynomial = 0x04c11db7;
// 256 values representing ASCII character codes.
for ( $i = 0; $i <= 0xFF; ++$i )
{
self::$crc32Table[$i] = ( self::crc32Reflect( $i, 8 ) << 24 );
for ( $j = 0; $j < 8; ++$j )
{
self::$crc32Table[$i] = ( ( self::$crc32Table[$i] << 1 ) ^ ( ( self::$crc32Table[$i] & ( 1 << 31 ) ) ? $polynomial : 0 ) );
}
self::$crc32Table[$i] = self::crc32Reflect( self::$crc32Table[$i], 32 );
}
}
/**
* Reflects CRC bits in the lookup table
*
* This method is taken from the PHP user comments
* (http://no.php.net/manual/en/function.crc32.php).
*
* @param int $ref
* @param int $ch
* @return int
*/
protected static function crc32Reflect( $ref, $ch )
{
$value = 0;
// Swap bit 0 for bit 7, bit 1 for bit 6, etc.
for ( $i = 1; $i < ( $ch + 1 ); ++$i )
{
if ( $ref & 1 )
{
$value |= ( 1 << ( $ch - $i ) );
}
$ref = ( ( $ref >> 1 ) & 0x7fffffff );
}
return $value;
}
}
?>
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