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