File modules/util/ui/minifier/Base64VLQ.class.php

Last commit: Sun Oct 13 13:17:32 2024 +0200	Jan Dankert	New Minifier for CSS and JS: Leave JS Linebreaks as they are (for better debugging); Exploded CSS files (instead of a combined one), LESS is necessary but should be avoided in the future.


     1 <?php
     2 
     3 namespace util\ui\minifier;
     4 
     5 /**
     6  * Encode / Decode Base64 VLQ.
     7  *
     8  * @author bspot
     9  */
    10 class Base64VLQ {
    11 
    12 	public static $SHIFT = 5;
    13 	public static $MASK = 0x1F; // == (1 << SHIFT) == 0b00011111
    14 	public static $CONTINUATION_BIT = 0x20; // == (MASK - 1 ) == 0b00100000
    15 
    16 	public static $CHAR_TO_INT = array();
    17 	public static $INT_TO_CHAR = array();
    18 
    19 	/**
    20 	 * Convert from a two-complement value to a value where the sign bit is
    21 	 * is placed in the least significant bit.  For example, as decimals:
    22 	 *   1 becomes 2 (10 binary), -1 becomes 3 (11 binary)
    23 	 *   2 becomes 4 (100 binary), -2 becomes 5 (101 binary)
    24 	 * We generate the value for 32 bit machines, hence
    25 	 *   -2147483648 becomes 1, not 4294967297,
    26 	 * even on a 64 bit machine.
    27 	 */
    28 	public static function toVLQSigned($aValue) {
    29 		return 0xffffffff & ($aValue < 0 ? ((-$aValue) << 1) + 1 : ($aValue << 1) + 0);
    30 	}
    31 
    32 	/**
    33 	 * Convert to a two-complement value from a value where the sign bit is
    34 	 * is placed in the least significant bit. For example, as decimals:
    35 	 *   2 (10 binary) becomes 1, 3 (11 binary) becomes -1
    36 	 *   4 (100 binary) becomes 2, 5 (101 binary) becomes -2
    37 	 * We assume that the value was generated with a 32 bit machine in mind.
    38 	 * Hence
    39 	 *   1 becomes -2147483648
    40 	 * even on a 64 bit machine.
    41 	 */
    42 	public static function fromVLQSigned($aValue) {
    43 		return $aValue & 1 ? self::zeroFill(~$aValue+2, 1) | (-1 - 0x7fffffff) : self::zeroFill($aValue, 1);
    44 	}
    45 
    46 	/**
    47 	 * Return the base 64 VLQ encoded value.
    48 	 */
    49 	public static function encode($aValue) {
    50 		$encoded = "";
    51 
    52 		$vlq = self::toVLQSigned($aValue);
    53 
    54 		do {
    55 			$digit = $vlq & self::$MASK;
    56 			$vlq = self::zeroFill($vlq, self::$SHIFT);
    57 			if ($vlq > 0) {
    58 				$digit |= self::$CONTINUATION_BIT;
    59 			}
    60 			$encoded .= self::base64Encode($digit);
    61 		} while ($vlq > 0);
    62 
    63 		return $encoded;
    64 	}
    65 
    66 	/**
    67 	 * Return the value decoded from base 64 VLQ.
    68 	 */
    69 	public static function decode($encoded) {
    70 		$vlq = 0;
    71 
    72 		$i = 0;
    73 		do {
    74 			$digit = self::base64Decode($encoded[$i]);
    75 			$vlq |= ($digit & self::$MASK) << ($i*self::$SHIFT);
    76 			$i++;
    77 		} while ($digit & self::$CONTINUATION_BIT);
    78 
    79 		return self::fromVLQSigned($vlq);
    80 	}
    81 
    82 	/**
    83 	 * Right shift with zero fill.
    84 	 *
    85 	 * @param number $a number to shift
    86 	 * @param nunber $b number of bits to shift
    87 	 * @return number
    88 	 */
    89 	public static function zeroFill($a, $b) {
    90 		return ($a >= 0) ? ($a >> $b) : ($a >> $b) & (PHP_INT_MAX >> ($b-1));
    91 	}
    92 
    93 	/**
    94 	 * Encode single 6-bit digit as base64.
    95 	 *
    96 	 * @param number $number
    97 	 * @return string
    98 	 */
    99 	public static function base64Encode($number) {
   100 		if ($number < 0 || $number > 63) {
   101 			throw new Exception("Must be between 0 and 63: " . $number);
   102 		}
   103 		return self::$INT_TO_CHAR[$number];
   104 	}
   105 
   106 	/**
   107 	 * Decode single 6-bit digit from base64
   108 	 *
   109 	 * @param string $char
   110 	 * @return number
   111 	 */
   112 	public static function base64Decode($char) {
   113 		if (!array_key_exists($char, self::$CHAR_TO_INT)) {
   114 			throw new Exception("Not a valid base 64 digit: " . $char);
   115 		}
   116 		return self::$CHAR_TO_INT[$char];
   117 	}
   118 }
   119 
   120 // Initialize char conversion table.
   121 Base64VLQ::$CHAR_TO_INT = array();
   122 Base64VLQ::$INT_TO_CHAR = array();
   123 
   124 foreach (str_split('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/') as $i => $char) {
   125 	Base64VLQ::$CHAR_TO_INT[$char] = $i;
   126 	Base64VLQ::$INT_TO_CHAR[$i] = $char;
   127 }



Download modules/util/ui/minifier/Base64VLQ.class.php


History
Sun, 13 Oct 2024 13:17:32 +0200	Jan Dankert	New Minifier for CSS and JS: Leave JS Linebreaks as they are (for better debugging); Exploded CSS files (instead of a combined one), LESS is necessary but should be avoided in the future.