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<?php |
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namespace IPLib\Service; |
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/** |
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* Helper class to work with unsigned binary integers. |
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* |
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* @internal |
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*/ |
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class BinaryMath |
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{ |
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/** |
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* Trim the leading zeroes from a non-negative integer represented in binary form. |
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* |
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* @param string $value |
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* |
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* @return string |
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*/ |
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1027 |
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public function reduce($value) |
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{ |
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1027 |
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$value = ltrim($value, '0'); |
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1027 |
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return $value === '' ? '0' : $value; |
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} |
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/** |
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* Compare two non-negative integers represented in binary form. |
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* |
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* @param string $a |
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* @param string $b |
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* |
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* @return int 1 if $a is greater than $b, -1 if $b is greater than $b, 0 if they are the same |
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*/ |
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public function compare($a, $b) |
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{ |
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list($a, $b) = $this->toSameLength($a, $b); |
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return $a < $b ? -1 : ($a > $b ? 1 : 0); |
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} |
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/** |
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* Add 1 to a non-negative integer represented in binary form. |
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* |
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* @param string $value |
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* |
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* @return string |
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*/ |
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155 |
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public function increment($value) |
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{ |
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155 |
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$lastZeroIndex = strrpos($value, '0'); |
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155 |
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if ($lastZeroIndex === false) { |
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return '1' . str_repeat('0', strlen($value)); |
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} |
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return ltrim(substr($value, 0, $lastZeroIndex), '0') . '1' . str_repeat('0', strlen($value) - $lastZeroIndex - 1); |
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} |
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/** |
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* Calculate the bitwise AND of two non-negative integers represented in binary form. |
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* |
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* @param string $operand1 |
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* @param string $operand2 |
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* |
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* @return string |
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*/ |
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516 |
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public function andX($operand1, $operand2) |
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{ |
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516 |
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$operand1 = $this->reduce($operand1); |
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516 |
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$operand2 = $this->reduce($operand2); |
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516 |
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$numBits = min(strlen($operand1), strlen($operand2)); |
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516 |
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$operand1 = substr(str_pad($operand1, $numBits, '0', STR_PAD_LEFT), -$numBits); |
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$operand2 = substr(str_pad($operand2, $numBits, '0', STR_PAD_LEFT), -$numBits); |
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$result = ''; |
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for ($index = 0; $index < $numBits; $index++) { |
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$result .= $operand1[$index] === '1' && $operand2[$index] === '1' ? '1' : '0'; |
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} |
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return $this->reduce($result); |
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} |
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/** |
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* Calculate the bitwise OR of two non-negative integers represented in binary form. |
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* |
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* @param string $operand1 |
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* @param string $operand2 |
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* |
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* @return string |
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*/ |
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501 |
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public function orX($operand1, $operand2) |
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{ |
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501 |
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list($operand1, $operand2, $numBits) = $this->toSameLength($operand1, $operand2); |
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$result = ''; |
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for ($index = 0; $index < $numBits; $index++) { |
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$result .= $operand1[$index] === '1' || $operand2[$index] === '1' ? '1' : '0'; |
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} |
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return $result; |
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} |
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/** |
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* Zero-padding of two non-negative integers represented in binary form, so that they have the same length. |
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* |
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* @param string $num1 |
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* @param string $num2 |
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* |
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* @return string[],int[] The first array element is $num1 (padded), the first array element is $num2 (padded), the third array element is the number of bits |
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*/ |
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private function toSameLength($num1, $num2) |
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{ |
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$num1 = $this->reduce($num1); |
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$num2 = $this->reduce($num2); |
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$numBits = max(strlen($num1), strlen($num2)); |
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return array( |
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str_pad($num1, $numBits, '0', STR_PAD_LEFT), |
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str_pad($num2, $numBits, '0', STR_PAD_LEFT), |
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$numBits, |
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); |
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} |
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} |
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mlocati /
ip-lib
