UnsignedIntegerMath.php
| 1 | <?php |
| 2 | |
| 3 | namespace IAWPSCOPED\IPLib\Service; |
| 4 | |
| 5 | /** |
| 6 | * Helper class to work with unsigned integers. |
| 7 | * |
| 8 | * @internal |
| 9 | */ |
| 10 | class UnsignedIntegerMath |
| 11 | { |
| 12 | /** |
| 13 | * Convert a string containing a decimal, octal or hexadecimal number into its bytes. |
| 14 | * |
| 15 | * @param string $value |
| 16 | * @param int $numBytes the wanted number of bytes |
| 17 | * @param bool $onlyDecimal Only parse decimal numbers |
| 18 | * |
| 19 | * @return int[]|null |
| 20 | */ |
| 21 | public function getBytes($value, $numBytes, $onlyDecimal = \false) |
| 22 | { |
| 23 | $m = null; |
| 24 | if ($onlyDecimal) { |
| 25 | if (\preg_match('/^0*(\\d+)$/', $value, $m)) { |
| 26 | return $this->getBytesFromDecimal($m[1], $numBytes); |
| 27 | } |
| 28 | } else { |
| 29 | if (\preg_match('/^0[Xx]0*([0-9A-Fa-f]+)$/', $value, $m)) { |
| 30 | return $this->getBytesFromHexadecimal($m[1], $numBytes); |
| 31 | } |
| 32 | if (\preg_match('/^0+([0-7]*)$/', $value, $m)) { |
| 33 | return $this->getBytesFromOctal($m[1], $numBytes); |
| 34 | } |
| 35 | if (\preg_match('/^[1-9][0-9]*$/', $value)) { |
| 36 | return $this->getBytesFromDecimal($value, $numBytes); |
| 37 | } |
| 38 | } |
| 39 | // Not a valid number |
| 40 | return null; |
| 41 | } |
| 42 | /** |
| 43 | * @return int |
| 44 | */ |
| 45 | protected function getMaxSignedInt() |
| 46 | { |
| 47 | return \PHP_INT_MAX; |
| 48 | } |
| 49 | /** |
| 50 | * @param string $value never zero-length, never extra leading zeroes |
| 51 | * @param int $numBytes |
| 52 | * |
| 53 | * @return int[]|null |
| 54 | */ |
| 55 | private function getBytesFromBits($value, $numBytes) |
| 56 | { |
| 57 | $valueLength = \strlen($value); |
| 58 | if ($valueLength > $numBytes << 3) { |
| 59 | // overflow |
| 60 | return null; |
| 61 | } |
| 62 | $remainderBits = $valueLength % 8; |
| 63 | if ($remainderBits !== 0) { |
| 64 | $value = \str_pad($value, $valueLength + 8 - $remainderBits, '0', \STR_PAD_LEFT); |
| 65 | } |
| 66 | $bytes = \array_map('bindec', \str_split($value, 8)); |
| 67 | return \array_pad($bytes, -$numBytes, 0); |
| 68 | } |
| 69 | /** |
| 70 | * @param string $value may be zero-length, never extra leading zeroes |
| 71 | * @param int $numBytes |
| 72 | * |
| 73 | * @return int[]|null |
| 74 | */ |
| 75 | private function getBytesFromOctal($value, $numBytes) |
| 76 | { |
| 77 | if ($value === '') { |
| 78 | return \array_fill(0, $numBytes, 0); |
| 79 | } |
| 80 | $bits = \implode('', \array_map(function ($octalDigit) { |
| 81 | return \str_pad(\decbin(\octdec($octalDigit)), 3, '0', \STR_PAD_LEFT); |
| 82 | }, \str_split($value, 1))); |
| 83 | $bits = \ltrim($bits, '0'); |
| 84 | return $bits === '' ? \array_fill(0, $numBytes, 0) : static::getBytesFromBits($bits, $numBytes); |
| 85 | } |
| 86 | /** |
| 87 | * @param string $value never zero-length, never extra leading zeroes |
| 88 | * @param int $numBytes |
| 89 | * |
| 90 | * @return int[]|null |
| 91 | */ |
| 92 | private function getBytesFromDecimal($value, $numBytes) |
| 93 | { |
| 94 | $valueLength = \strlen($value); |
| 95 | $maxSignedIntLength = \strlen((string) $this->getMaxSignedInt()); |
| 96 | if ($valueLength < $maxSignedIntLength) { |
| 97 | return $this->getBytesFromBits(\decbin((int) $value), $numBytes); |
| 98 | } |
| 99 | // Divide by two, so that we have 1 less bit |
| 100 | $carry = 0; |
| 101 | $halfValue = \ltrim(\implode('', \array_map(function ($digit) use(&$carry) { |
| 102 | $number = $carry + (int) $digit; |
| 103 | $carry = $number % 2 * 10; |
| 104 | return (string) $number >> 1; |
| 105 | }, \str_split($value, 1))), '0'); |
| 106 | $halfValueBytes = $this->getBytesFromDecimal($halfValue, $numBytes); |
| 107 | if ($halfValueBytes === null) { |
| 108 | return null; |
| 109 | } |
| 110 | $carry = $carry === 0 ? 0 : 1; |
| 111 | $result = \array_fill(0, $numBytes, 0); |
| 112 | for ($index = $numBytes - 1; $index >= 0; $index--) { |
| 113 | $byte = $carry + ($halfValueBytes[$index] << 1); |
| 114 | if ($byte <= 0xff) { |
| 115 | $carry = 0; |
| 116 | } else { |
| 117 | $carry = ($byte & ~0xff) >> 8; |
| 118 | $byte -= 0x100; |
| 119 | } |
| 120 | $result[$index] = $byte; |
| 121 | } |
| 122 | if ($carry !== 0) { |
| 123 | // Overflow |
| 124 | return null; |
| 125 | } |
| 126 | return $result; |
| 127 | } |
| 128 | /** |
| 129 | * @param string $value never zero-length, never extra leading zeroes |
| 130 | * @param int $numBytes |
| 131 | * |
| 132 | * @return int[]|null |
| 133 | */ |
| 134 | private function getBytesFromHexadecimal($value, $numBytes) |
| 135 | { |
| 136 | $valueLength = \strlen($value); |
| 137 | if ($valueLength > $numBytes << 1) { |
| 138 | // overflow |
| 139 | return null; |
| 140 | } |
| 141 | $value = \str_pad($value, $valueLength + $valueLength % 2, '0', \STR_PAD_LEFT); |
| 142 | $bytes = \array_map('hexdec', \str_split($value, 2)); |
| 143 | return \array_pad($bytes, -$numBytes, 0); |
| 144 | } |
| 145 | } |
| 146 |