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<?php /** * SCSSPHP * * @copyright 2012-2019 Leaf Corcoran * * @license http://opensource.org/licenses/MIT MIT * * @link http://scssphp.github.io/scssphp */ namespace ScssPhp\ScssPhp\SourceMap; use ScssPhp\ScssPhp\SourceMap\Base64; /** * Base 64 VLQ * * Based on the Base 64 VLQ implementation in Closure Compiler: * https://github.com/google/closure-compiler/blob/master/src/com/google/debugging/sourcemap/Base64VLQ.java * * Copyright 2011 The Closure Compiler Authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * * @author John Lenz <johnlenz@google.com> * @author Anthon Pang <anthon.pang@gmail.com> */ class Base64VLQ { // A Base64 VLQ digit can represent 5 bits, so it is base-32. const VLQ_BASE_SHIFT = 5; // A mask of bits for a VLQ digit (11111), 31 decimal. const VLQ_BASE_MASK = 31; // The continuation bit is the 6th bit. const VLQ_CONTINUATION_BIT = 32; /** * Returns the VLQ encoded value. * * @param integer $value * * @return string */ public static function encode($value) { $encoded = ''; $vlq = self::toVLQSigned($value); do { $digit = $vlq & self::VLQ_BASE_MASK; $vlq >>= self::VLQ_BASE_SHIFT; if ($vlq > 0) { $digit |= self::VLQ_CONTINUATION_BIT; } $encoded .= Base64::encode($digit); } while ($vlq > 0); return $encoded; } /** * Decodes VLQValue. * * @param string $str * @param integer $index * * @return integer */ public static function decode($str, &$index) { $result = 0; $shift = 0; do { $c = $str[$index++]; $digit = Base64::decode($c); $continuation = ($digit & self::VLQ_CONTINUATION_BIT) != 0; $digit &= self::VLQ_BASE_MASK; $result = $result + ($digit << $shift); $shift = $shift + self::VLQ_BASE_SHIFT; } while ($continuation); return self::fromVLQSigned($result); } /** * Converts 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) * * @param integer $value * * @return integer */ private static function toVLQSigned($value) { if ($value < 0) { return ((-$value) << 1) + 1; } return ($value << 1) + 0; } /** * Converts 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 * * @param integer $value * * @return integer */ private static function fromVLQSigned($value) { $negate = ($value & 1) === 1; $value = ($value >> 1) & ~(1<<(8 * PHP_INT_SIZE - 1)); // unsigned right shift if (! $negate) { return $value; } // We need to OR 0x80000000 here to ensure the 32nd bit (the sign bit) is // always set for negative numbers. If `value` were 1, (meaning `negate` is // true and all other bits were zeros), `value` would now be 0. -0 is just // 0, and doesn't flip the 32nd bit as intended. All positive numbers will // successfully flip the 32nd bit without issue, so it's a noop for them. return -$value | 0x80000000; } }