bitarray.php

<?php

class BitArray {

    //Sacrifice 2x the amount of memory, so we can use pack/unpack easily
    const INT_SIZE = 4;

    private $bitmapString;
    public function __construct($numberOfBits = 64, $bitmapString = null) {
        if($bitmapString!= null)
            $this->bitmapString = $bitmapString;
        else {
            if($numberOfBits == null)
                throw new InvalidArgumentException("numberOfBits or bitmapString is required");
            $numberOfInts = $numberOfBits / self::INT_SIZE / 8; // PHP_INT_SIZE is in bytes
            for($i = 0; $i < $numberOfInts; $i++) {
                $this->bitmapString .= pack("L", 0);
            }
        }
    }

    public function setBit($bit) {
        $this->bitmapString = $this->bitmapString | $this->getBitStr($bit);
    }

    public function unsetBit($bit) {
        $this->bitmapString = $this->bitmapString & (~($this->getBitStr($bit)));
    }

    private function getBitStr($bit) {
        $index = floor($bit / self::INT_SIZE / 8);
        $bitInIndex = $bit % (self::INT_SIZE * 8);
        $bitStr = "";
        for($i = 0; $i < $index; $i++) {
            $bitStr .= pack("L", 0);
        }
        $numToSet = pow(2, $bitInIndex);
        $bitStr .= pack("L", $numToSet);
        return $bitStr;
    }

    public function toIntArray() {
        $intIndex = 0;
        $retArray = array();
        for($j = 0; $j < $this->length(); $j += self::INT_SIZE) {
            $charsToUnpack = mb_substr($this->bitmapString, $j, self::INT_SIZE, '8bit');
            $intInArray = unpack("L", $charsToUnpack);
            $intInArray = $intInArray[1];
            for($i = 0; $i < (self::INT_SIZE * 8); $i++) {
                if(($intInArray | pow(2, $i)) == $intInArray) {
                    $retArray[] = $intIndex;
                }
                $intIndex++;
            }
        }
        return $retArray;
    }

    public function length() {
        return mb_strlen($this->bitmapString, '8bit');
    }

    public function __tostring() {
        return $this->bitmapString;
    }

    public static function orFn($thisBitArray, $thatBitArray) {
        return new BitArray(null, $thisBitArray->__tostring() | $thatBitArray->__tostring());
    }
}