--- /dev/null
+<?php
+
+/**
+ * Encode / Decode Base64 VLQ.
+ *
+ * @package Less
+ * @subpackage SourceMap
+ */
+class Less_SourceMap_Base64VLQ {
+
+ /**
+ * Shift
+ *
+ * @var integer
+ */
+ private $shift = 5;
+
+ /**
+ * Mask
+ *
+ * @var integer
+ */
+ private $mask = 0x1F; // == (1 << shift) == 0b00011111
+
+ /**
+ * Continuation bit
+ *
+ * @var integer
+ */
+ private $continuationBit = 0x20; // == (mask - 1 ) == 0b00100000
+
+ /**
+ * Char to integer map
+ *
+ * @var array
+ */
+ private $charToIntMap = array(
+ 'A' => 0, 'B' => 1, 'C' => 2, 'D' => 3, 'E' => 4, 'F' => 5, 'G' => 6,
+ 'H' => 7,'I' => 8, 'J' => 9, 'K' => 10, 'L' => 11, 'M' => 12, 'N' => 13,
+ 'O' => 14, 'P' => 15, 'Q' => 16, 'R' => 17, 'S' => 18, 'T' => 19, 'U' => 20,
+ 'V' => 21, 'W' => 22, 'X' => 23, 'Y' => 24, 'Z' => 25, 'a' => 26, 'b' => 27,
+ 'c' => 28, 'd' => 29, 'e' => 30, 'f' => 31, 'g' => 32, 'h' => 33, 'i' => 34,
+ 'j' => 35, 'k' => 36, 'l' => 37, 'm' => 38, 'n' => 39, 'o' => 40, 'p' => 41,
+ 'q' => 42, 'r' => 43, 's' => 44, 't' => 45, 'u' => 46, 'v' => 47, 'w' => 48,
+ 'x' => 49, 'y' => 50, 'z' => 51, 0 => 52, 1 => 53, 2 => 54, 3 => 55, 4 => 56,
+ 5 => 57, 6 => 58, 7 => 59, 8 => 60, 9 => 61, '+' => 62, '/' => 63,
+ );
+
+ /**
+ * Integer to char map
+ *
+ * @var array
+ */
+ private $intToCharMap = array(
+ 0 => 'A', 1 => 'B', 2 => 'C', 3 => 'D', 4 => 'E', 5 => 'F', 6 => 'G',
+ 7 => 'H', 8 => 'I', 9 => 'J', 10 => 'K', 11 => 'L', 12 => 'M', 13 => 'N',
+ 14 => 'O', 15 => 'P', 16 => 'Q', 17 => 'R', 18 => 'S', 19 => 'T', 20 => 'U',
+ 21 => 'V', 22 => 'W', 23 => 'X', 24 => 'Y', 25 => 'Z', 26 => 'a', 27 => 'b',
+ 28 => 'c', 29 => 'd', 30 => 'e', 31 => 'f', 32 => 'g', 33 => 'h', 34 => 'i',
+ 35 => 'j', 36 => 'k', 37 => 'l', 38 => 'm', 39 => 'n', 40 => 'o', 41 => 'p',
+ 42 => 'q', 43 => 'r', 44 => 's', 45 => 't', 46 => 'u', 47 => 'v', 48 => 'w',
+ 49 => 'x', 50 => 'y', 51 => 'z', 52 => '0', 53 => '1', 54 => '2', 55 => '3',
+ 56 => '4', 57 => '5', 58 => '6', 59 => '7', 60 => '8', 61 => '9', 62 => '+',
+ 63 => '/',
+ );
+
+ /**
+ * Constructor
+ */
+ public function __construct(){
+ // I leave it here for future reference
+ // foreach(str_split('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/') as $i => $char)
+ // {
+ // $this->charToIntMap[$char] = $i;
+ // $this->intToCharMap[$i] = $char;
+ // }
+ }
+
+ /**
+ * Convert from a two-complement value to a value where the sign bit is
+ * is placed in the least significant bit. For example, as decimals:
+ * 1 becomes 2 (10 binary), -1 becomes 3 (11 binary)
+ * 2 becomes 4 (100 binary), -2 becomes 5 (101 binary)
+ * We generate the value for 32 bit machines, hence -2147483648 becomes 1, not 4294967297,
+ * even on a 64 bit machine.
+ * @param string $aValue
+ */
+ public function toVLQSigned($aValue){
+ return 0xffffffff & ($aValue < 0 ? ((-$aValue) << 1) + 1 : ($aValue << 1) + 0);
+ }
+
+ /**
+ * Convert to a two-complement value from a value where the sign bit is
+ * is placed in the least significant bit. For example, as decimals:
+ * 2 (10 binary) becomes 1, 3 (11 binary) becomes -1
+ * 4 (100 binary) becomes 2, 5 (101 binary) becomes -2
+ * We assume that the value was generated with a 32 bit machine in mind.
+ * Hence
+ * 1 becomes -2147483648
+ * even on a 64 bit machine.
+ * @param integer $aValue
+ */
+ public function fromVLQSigned($aValue){
+ return $aValue & 1 ? $this->zeroFill(~$aValue + 2, 1) | (-1 - 0x7fffffff) : $this->zeroFill($aValue, 1);
+ }
+
+ /**
+ * Return the base 64 VLQ encoded value.
+ *
+ * @param string $aValue The value to encode
+ * @return string The encoded value
+ */
+ public function encode($aValue){
+ $encoded = '';
+ $vlq = $this->toVLQSigned($aValue);
+ do
+ {
+ $digit = $vlq & $this->mask;
+ $vlq = $this->zeroFill($vlq, $this->shift);
+ if($vlq > 0){
+ $digit |= $this->continuationBit;
+ }
+ $encoded .= $this->base64Encode($digit);
+ } while($vlq > 0);
+
+ return $encoded;
+ }
+
+ /**
+ * Return the value decoded from base 64 VLQ.
+ *
+ * @param string $encoded The encoded value to decode
+ * @return integer The decoded value
+ */
+ public function decode($encoded){
+ $vlq = 0;
+ $i = 0;
+ do
+ {
+ $digit = $this->base64Decode($encoded[$i]);
+ $vlq |= ($digit & $this->mask) << ($i * $this->shift);
+ $i++;
+ } while($digit & $this->continuationBit);
+
+ return $this->fromVLQSigned($vlq);
+ }
+
+ /**
+ * Right shift with zero fill.
+ *
+ * @param integer $a number to shift
+ * @param integer $b number of bits to shift
+ * @return integer
+ */
+ public function zeroFill($a, $b){
+ return ($a >= 0) ? ($a >> $b) : ($a >> $b) & (PHP_INT_MAX >> ($b - 1));
+ }
+
+ /**
+ * Encode single 6-bit digit as base64.
+ *
+ * @param integer $number
+ * @return string
+ * @throws Exception If the number is invalid
+ */
+ public function base64Encode($number){
+ if($number < 0 || $number > 63){
+ throw new Exception(sprintf('Invalid number "%s" given. Must be between 0 and 63.', $number));
+ }
+ return $this->intToCharMap[$number];
+ }
+
+ /**
+ * Decode single 6-bit digit from base64
+ *
+ * @param string $char
+ * @return number
+ * @throws Exception If the number is invalid
+ */
+ public function base64Decode($char){
+ if(!array_key_exists($char, $this->charToIntMap)){
+ throw new Exception(sprintf('Invalid base 64 digit "%s" given.', $char));
+ }
+ return $this->charToIntMap[$char];
+ }
+
+}
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