Viewing file:  BitArray.php (8.71 KB) -rw-r--r--
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<?php
declare(strict_types = 1);
namespace BaconQrCode\Common;
use BaconQrCode\Exception\InvalidArgumentException;
use SplFixedArray;
/**
* A simple, fast array of bits.
*/
final class BitArray
{
/**
* Bits represented as an array of integers.
*
* @var SplFixedArray<int>
*/
private $bits;
/**
* Size of the bit array in bits.
*
* @var int
*/
private $size;
/**
* Creates a new bit array with a given size.
*/
public function __construct(int $size = 0)
{
$this->size = $size;
$this->bits = SplFixedArray::fromArray(array_fill(0, ($this->size + 31) >> 3, 0));
}
/**
* Gets the size in bits.
*/
public function getSize() : int
{
return $this->size;
}
/**
* Gets the size in bytes.
*/
public function getSizeInBytes() : int
{
return ($this->size + 7) >> 3;
}
/**
* Ensures that the array has a minimum capacity.
*/
public function ensureCapacity(int $size) : void
{
if ($size > count($this->bits) << 5) {
$this->bits->setSize(($size + 31) >> 5);
}
}
/**
* Gets a specific bit.
*/
public function get(int $i) : bool
{
return 0 !== ($this->bits[$i >> 5] & (1 << ($i & 0x1f)));
}
/**
* Sets a specific bit.
*/
public function set(int $i) : void
{
$this->bits[$i >> 5] = $this->bits[$i >> 5] | 1 << ($i & 0x1f);
}
/**
* Flips a specific bit.
*/
public function flip(int $i) : void
{
$this->bits[$i >> 5] ^= 1 << ($i & 0x1f);
}
/**
* Gets the next set bit position from a given position.
*/
public function getNextSet(int $from) : int
{
if ($from >= $this->size) {
return $this->size;
}
$bitsOffset = $from >> 5;
$currentBits = $this->bits[$bitsOffset];
$bitsLength = count($this->bits);
$currentBits &= ~((1 << ($from & 0x1f)) - 1);
while (0 === $currentBits) {
if (++$bitsOffset === $bitsLength) {
return $this->size;
}
$currentBits = $this->bits[$bitsOffset];
}
$result = ($bitsOffset << 5) + BitUtils::numberOfTrailingZeros($currentBits);
return $result > $this->size ? $this->size : $result;
}
/**
* Gets the next unset bit position from a given position.
*/
public function getNextUnset(int $from) : int
{
if ($from >= $this->size) {
return $this->size;
}
$bitsOffset = $from >> 5;
$currentBits = ~$this->bits[$bitsOffset];
$bitsLength = count($this->bits);
$currentBits &= ~((1 << ($from & 0x1f)) - 1);
while (0 === $currentBits) {
if (++$bitsOffset === $bitsLength) {
return $this->size;
}
$currentBits = ~$this->bits[$bitsOffset];
}
$result = ($bitsOffset << 5) + BitUtils::numberOfTrailingZeros($currentBits);
return $result > $this->size ? $this->size : $result;
}
/**
* Sets a bulk of bits.
*/
public function setBulk(int $i, int $newBits) : void
{
$this->bits[$i >> 5] = $newBits;
}
/**
* Sets a range of bits.
*
* @throws InvalidArgumentException if end is smaller than start
*/
public function setRange(int $start, int $end) : void
{
if ($end < $start) {
throw new InvalidArgumentException('End must be greater or equal to start');
}
if ($end === $start) {
return;
}
--$end;
$firstInt = $start >> 5;
$lastInt = $end >> 5;
for ($i = $firstInt; $i <= $lastInt; ++$i) {
$firstBit = $i > $firstInt ? 0 : $start & 0x1f;
$lastBit = $i < $lastInt ? 31 : $end & 0x1f;
if (0 === $firstBit && 31 === $lastBit) {
$mask = 0x7fffffff;
} else {
$mask = 0;
for ($j = $firstBit; $j < $lastBit; ++$j) {
$mask |= 1 << $j;
}
}
$this->bits[$i] = $this->bits[$i] | $mask;
}
}
/**
* Clears the bit array, unsetting every bit.
*/
public function clear() : void
{
$bitsLength = count($this->bits);
for ($i = 0; $i < $bitsLength; ++$i) {
$this->bits[$i] = 0;
}
}
/**
* Checks if a range of bits is set or not set.
* @throws InvalidArgumentException if end is smaller than start
*/
public function isRange(int $start, int $end, bool $value) : bool
{
if ($end < $start) {
throw new InvalidArgumentException('End must be greater or equal to start');
}
if ($end === $start) {
return true;
}
--$end;
$firstInt = $start >> 5;
$lastInt = $end >> 5;
for ($i = $firstInt; $i <= $lastInt; ++$i) {
$firstBit = $i > $firstInt ? 0 : $start & 0x1f;
$lastBit = $i < $lastInt ? 31 : $end & 0x1f;
if (0 === $firstBit && 31 === $lastBit) {
$mask = 0x7fffffff;
} else {
$mask = 0;
for ($j = $firstBit; $j <= $lastBit; ++$j) {
$mask |= 1 << $j;
}
}
if (($this->bits[$i] & $mask) !== ($value ? $mask : 0)) {
return false;
}
}
return true;
}
/**
* Appends a bit to the array.
*/
public function appendBit(bool $bit) : void
{
$this->ensureCapacity($this->size + 1);
if ($bit) {
$this->bits[$this->size >> 5] = $this->bits[$this->size >> 5] | (1 << ($this->size & 0x1f));
}
++$this->size;
}
/**
* Appends a number of bits (up to 32) to the array.
* @throws InvalidArgumentException if num bits is not between 0 and 32
*/
public function appendBits(int $value, int $numBits) : void
{
if ($numBits < 0 || $numBits > 32) {
throw new InvalidArgumentException('Num bits must be between 0 and 32');
}
$this->ensureCapacity($this->size + $numBits);
for ($numBitsLeft = $numBits; $numBitsLeft > 0; $numBitsLeft--) {
$this->appendBit((($value >> ($numBitsLeft - 1)) & 0x01) === 1);
}
}
/**
* Appends another bit array to this array.
*/
public function appendBitArray(self $other) : void
{
$otherSize = $other->getSize();
$this->ensureCapacity($this->size + $other->getSize());
for ($i = 0; $i < $otherSize; ++$i) {
$this->appendBit($other->get($i));
}
}
/**
* Makes an exclusive-or comparision on the current bit array.
*
* @throws InvalidArgumentException if sizes don't match
*/
public function xorBits(self $other) : void
{
$bitsLength = count($this->bits);
$otherBits = $other->getBitArray();
if ($bitsLength !== count($otherBits)) {
throw new InvalidArgumentException('Sizes don\'t match');
}
for ($i = 0; $i < $bitsLength; ++$i) {
$this->bits[$i] = $this->bits[$i] ^ $otherBits[$i];
}
}
/**
* Converts the bit array to a byte array.
*
* @return SplFixedArray<int>
*/
public function toBytes(int $bitOffset, int $numBytes) : SplFixedArray
{
$bytes = new SplFixedArray($numBytes);
for ($i = 0; $i < $numBytes; ++$i) {
$byte = 0;
for ($j = 0; $j < 8; ++$j) {
if ($this->get($bitOffset)) {
$byte |= 1 << (7 - $j);
}
++$bitOffset;
}
$bytes[$i] = $byte;
}
return $bytes;
}
/**
* Gets the internal bit array.
*
* @return SplFixedArray<int>
*/
public function getBitArray() : SplFixedArray
{
return $this->bits;
}
/**
* Reverses the array.
*/
public function reverse() : void
{
$newBits = new SplFixedArray(count($this->bits));
for ($i = 0; $i < $this->size; ++$i) {
if ($this->get($this->size - $i - 1)) {
$newBits[$i >> 5] = $newBits[$i >> 5] | (1 << ($i & 0x1f));
}
}
$this->bits = $newBits;
}
/**
* Returns a string representation of the bit array.
*/
public function __toString() : string
{
$result = '';
for ($i = 0; $i < $this->size; ++$i) {
if (0 === ($i & 0x07)) {
$result .= ' ';
}
$result .= $this->get($i) ? 'X' : '.';
}
return $result;
}
}
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