373 lines
8.7 KiB
PHP
373 lines
8.7 KiB
PHP
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<?php
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declare(strict_types = 1);
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namespace BaconQrCode\Common;
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use BaconQrCode\Exception\InvalidArgumentException;
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use SplFixedArray;
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/**
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* A simple, fast array of bits.
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*/
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final class BitArray
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{
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/**
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* Bits represented as an array of integers.
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*
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* @var SplFixedArray<int>
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*/
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private $bits;
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/**
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* Size of the bit array in bits.
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*
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* @var int
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*/
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private $size;
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/**
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* Creates a new bit array with a given size.
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*/
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public function __construct(int $size = 0)
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{
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$this->size = $size;
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$this->bits = SplFixedArray::fromArray(array_fill(0, ($this->size + 31) >> 3, 0));
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}
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/**
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* Gets the size in bits.
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*/
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public function getSize() : int
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{
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return $this->size;
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}
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/**
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* Gets the size in bytes.
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*/
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public function getSizeInBytes() : int
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{
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return ($this->size + 7) >> 3;
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}
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/**
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* Ensures that the array has a minimum capacity.
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*/
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public function ensureCapacity(int $size) : void
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{
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if ($size > count($this->bits) << 5) {
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$this->bits->setSize(($size + 31) >> 5);
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}
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}
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/**
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* Gets a specific bit.
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*/
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public function get(int $i) : bool
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{
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return 0 !== ($this->bits[$i >> 5] & (1 << ($i & 0x1f)));
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}
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/**
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* Sets a specific bit.
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*/
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public function set(int $i) : void
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{
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$this->bits[$i >> 5] = $this->bits[$i >> 5] | 1 << ($i & 0x1f);
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}
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/**
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* Flips a specific bit.
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*/
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public function flip(int $i) : void
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{
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$this->bits[$i >> 5] ^= 1 << ($i & 0x1f);
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}
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/**
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* Gets the next set bit position from a given position.
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*/
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public function getNextSet(int $from) : int
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{
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if ($from >= $this->size) {
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return $this->size;
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}
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$bitsOffset = $from >> 5;
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$currentBits = $this->bits[$bitsOffset];
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$bitsLength = count($this->bits);
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$currentBits &= ~((1 << ($from & 0x1f)) - 1);
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while (0 === $currentBits) {
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if (++$bitsOffset === $bitsLength) {
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return $this->size;
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}
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$currentBits = $this->bits[$bitsOffset];
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}
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$result = ($bitsOffset << 5) + BitUtils::numberOfTrailingZeros($currentBits);
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return $result > $this->size ? $this->size : $result;
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}
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/**
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* Gets the next unset bit position from a given position.
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*/
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public function getNextUnset(int $from) : int
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{
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if ($from >= $this->size) {
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return $this->size;
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}
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$bitsOffset = $from >> 5;
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$currentBits = ~$this->bits[$bitsOffset];
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$bitsLength = count($this->bits);
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$currentBits &= ~((1 << ($from & 0x1f)) - 1);
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while (0 === $currentBits) {
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if (++$bitsOffset === $bitsLength) {
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return $this->size;
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}
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$currentBits = ~$this->bits[$bitsOffset];
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}
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$result = ($bitsOffset << 5) + BitUtils::numberOfTrailingZeros($currentBits);
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return $result > $this->size ? $this->size : $result;
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}
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/**
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* Sets a bulk of bits.
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*/
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public function setBulk(int $i, int $newBits) : void
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{
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$this->bits[$i >> 5] = $newBits;
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}
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/**
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* Sets a range of bits.
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*
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* @throws InvalidArgumentException if end is smaller than start
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*/
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public function setRange(int $start, int $end) : void
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{
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if ($end < $start) {
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throw new InvalidArgumentException('End must be greater or equal to start');
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}
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if ($end === $start) {
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return;
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}
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--$end;
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$firstInt = $start >> 5;
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$lastInt = $end >> 5;
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for ($i = $firstInt; $i <= $lastInt; ++$i) {
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$firstBit = $i > $firstInt ? 0 : $start & 0x1f;
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$lastBit = $i < $lastInt ? 31 : $end & 0x1f;
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if (0 === $firstBit && 31 === $lastBit) {
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$mask = 0x7fffffff;
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} else {
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$mask = 0;
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for ($j = $firstBit; $j < $lastBit; ++$j) {
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$mask |= 1 << $j;
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}
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}
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$this->bits[$i] = $this->bits[$i] | $mask;
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}
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}
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/**
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* Clears the bit array, unsetting every bit.
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*/
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public function clear() : void
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{
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$bitsLength = count($this->bits);
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for ($i = 0; $i < $bitsLength; ++$i) {
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$this->bits[$i] = 0;
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}
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}
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/**
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* Checks if a range of bits is set or not set.
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* @throws InvalidArgumentException if end is smaller than start
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*/
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public function isRange(int $start, int $end, bool $value) : bool
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{
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if ($end < $start) {
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throw new InvalidArgumentException('End must be greater or equal to start');
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}
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if ($end === $start) {
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return true;
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}
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--$end;
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$firstInt = $start >> 5;
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$lastInt = $end >> 5;
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for ($i = $firstInt; $i <= $lastInt; ++$i) {
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$firstBit = $i > $firstInt ? 0 : $start & 0x1f;
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$lastBit = $i < $lastInt ? 31 : $end & 0x1f;
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if (0 === $firstBit && 31 === $lastBit) {
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$mask = 0x7fffffff;
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} else {
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$mask = 0;
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for ($j = $firstBit; $j <= $lastBit; ++$j) {
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$mask |= 1 << $j;
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}
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}
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if (($this->bits[$i] & $mask) !== ($value ? $mask : 0)) {
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return false;
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}
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}
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return true;
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}
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/**
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* Appends a bit to the array.
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*/
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public function appendBit(bool $bit) : void
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{
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$this->ensureCapacity($this->size + 1);
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if ($bit) {
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$this->bits[$this->size >> 5] = $this->bits[$this->size >> 5] | (1 << ($this->size & 0x1f));
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}
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++$this->size;
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}
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/**
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* Appends a number of bits (up to 32) to the array.
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* @throws InvalidArgumentException if num bits is not between 0 and 32
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*/
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public function appendBits(int $value, int $numBits) : void
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{
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if ($numBits < 0 || $numBits > 32) {
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throw new InvalidArgumentException('Num bits must be between 0 and 32');
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}
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$this->ensureCapacity($this->size + $numBits);
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for ($numBitsLeft = $numBits; $numBitsLeft > 0; $numBitsLeft--) {
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$this->appendBit((($value >> ($numBitsLeft - 1)) & 0x01) === 1);
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}
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}
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/**
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* Appends another bit array to this array.
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*/
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public function appendBitArray(self $other) : void
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{
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$otherSize = $other->getSize();
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$this->ensureCapacity($this->size + $other->getSize());
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for ($i = 0; $i < $otherSize; ++$i) {
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$this->appendBit($other->get($i));
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}
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}
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/**
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* Makes an exclusive-or comparision on the current bit array.
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*
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* @throws InvalidArgumentException if sizes don't match
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*/
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public function xorBits(self $other) : void
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{
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$bitsLength = count($this->bits);
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$otherBits = $other->getBitArray();
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if ($bitsLength !== count($otherBits)) {
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throw new InvalidArgumentException('Sizes don\'t match');
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}
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for ($i = 0; $i < $bitsLength; ++$i) {
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$this->bits[$i] = $this->bits[$i] ^ $otherBits[$i];
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}
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}
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/**
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* Converts the bit array to a byte array.
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*
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* @return SplFixedArray<int>
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*/
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public function toBytes(int $bitOffset, int $numBytes) : SplFixedArray
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{
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$bytes = new SplFixedArray($numBytes);
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for ($i = 0; $i < $numBytes; ++$i) {
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$byte = 0;
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for ($j = 0; $j < 8; ++$j) {
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if ($this->get($bitOffset)) {
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$byte |= 1 << (7 - $j);
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}
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++$bitOffset;
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}
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$bytes[$i] = $byte;
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}
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return $bytes;
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}
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/**
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* Gets the internal bit array.
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*
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* @return SplFixedArray<int>
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*/
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public function getBitArray() : SplFixedArray
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{
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return $this->bits;
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}
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/**
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* Reverses the array.
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*/
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public function reverse() : void
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{
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$newBits = new SplFixedArray(count($this->bits));
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for ($i = 0; $i < $this->size; ++$i) {
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if ($this->get($this->size - $i - 1)) {
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$newBits[$i >> 5] = $newBits[$i >> 5] | (1 << ($i & 0x1f));
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}
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}
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$this->bits = $newBits;
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}
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/**
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* Returns a string representation of the bit array.
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*/
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public function __toString() : string
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{
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$result = '';
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for ($i = 0; $i < $this->size; ++$i) {
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if (0 === ($i & 0x07)) {
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$result .= ' ';
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}
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$result .= $this->get($i) ? 'X' : '.';
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}
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return $result;
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}
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}
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