180 lines
3.5 KiB
PHP
180 lines
3.5 KiB
PHP
<?php
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/**
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* Class BitBuffer
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*
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* @created 25.11.2015
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* @author Smiley <smiley@chillerlan.net>
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* @copyright 2015 Smiley
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* @license MIT
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*/
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namespace chillerlan\QRCode\Common;
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use chillerlan\QRCode\QRCodeException;
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use function count, floor, min;
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/**
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* Holds the raw binary data
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*/
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final class BitBuffer{
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/**
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* The buffer content
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*
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* @var int[]
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*/
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private array $buffer;
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/**
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* Length of the content (bits)
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*/
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private int $length;
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/**
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* Read count (bytes)
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*/
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private int $bytesRead = 0;
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/**
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* Read count (bits)
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*/
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private int $bitsRead = 0;
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/**
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* BitBuffer constructor.
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*
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* @param int[] $bytes
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*/
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public function __construct(array $bytes = []){
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$this->buffer = $bytes;
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$this->length = count($this->buffer);
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}
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/**
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* appends a sequence of bits
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*/
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public function put(int $bits, int $length):self{
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for($i = 0; $i < $length; $i++){
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$this->putBit((($bits >> ($length - $i - 1)) & 1) === 1);
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}
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return $this;
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}
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/**
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* appends a single bit
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*/
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public function putBit(bool $bit):self{
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$bufIndex = (int)floor($this->length / 8);
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if(count($this->buffer) <= $bufIndex){
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$this->buffer[] = 0;
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}
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if($bit === true){
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$this->buffer[$bufIndex] |= (0x80 >> ($this->length % 8));
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}
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$this->length++;
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return $this;
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}
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/**
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* returns the current buffer length
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*/
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public function getLength():int{
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return $this->length;
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}
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/**
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* returns the buffer content
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*
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* to debug: array_map(fn($v) => sprintf('%08b', $v), $bitBuffer->getBuffer())
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*/
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public function getBuffer():array{
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return $this->buffer;
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}
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/**
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* @return int number of bits that can be read successfully
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*/
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public function available():int{
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return ((8 * ($this->length - $this->bytesRead)) - $this->bitsRead);
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}
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/**
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* @author Sean Owen, ZXing
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*
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* @param int $numBits number of bits to read
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*
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* @return int representing the bits read. The bits will appear as the least-significant bits of the int
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* @throws \chillerlan\QRCode\QRCodeException if numBits isn't in [1,32] or more than is available
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*/
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public function read(int $numBits):int{
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if($numBits < 1 || $numBits > $this->available()){
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throw new QRCodeException('invalid $numBits: '.$numBits);
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}
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$result = 0;
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// First, read remainder from current byte
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if($this->bitsRead > 0){
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$bitsLeft = (8 - $this->bitsRead);
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$toRead = min($numBits, $bitsLeft);
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$bitsToNotRead = ($bitsLeft - $toRead);
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$mask = ((0xff >> (8 - $toRead)) << $bitsToNotRead);
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$result = (($this->buffer[$this->bytesRead] & $mask) >> $bitsToNotRead);
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$numBits -= $toRead;
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$this->bitsRead += $toRead;
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if($this->bitsRead === 8){
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$this->bitsRead = 0;
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$this->bytesRead++;
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}
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}
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// Next read whole bytes
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if($numBits > 0){
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while($numBits >= 8){
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$result = (($result << 8) | ($this->buffer[$this->bytesRead] & 0xff));
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$this->bytesRead++;
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$numBits -= 8;
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}
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// Finally read a partial byte
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if($numBits > 0){
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$bitsToNotRead = (8 - $numBits);
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$mask = ((0xff >> $bitsToNotRead) << $bitsToNotRead);
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$result = (($result << $numBits) | (($this->buffer[$this->bytesRead] & $mask) >> $bitsToNotRead));
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$this->bitsRead += $numBits;
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}
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}
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return $result;
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}
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/**
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* Clears the buffer and resets the stats
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*/
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public function clear():self{
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$this->buffer = [];
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$this->length = 0;
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return $this->rewind();
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}
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/**
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* Resets the read-counters
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*/
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public function rewind():self{
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$this->bytesRead = 0;
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$this->bitsRead = 0;
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return $this;
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}
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}
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