A simple, fast array of bits, represented compactly by an array of ints internally.

* * @author Sean Owen */ final class BitArray { private $bits; private $size; public function __construct($bits = [], $size = 0) { if (!$bits && !$size) { $this->$size = 0; $this->bits = []; } elseif ($bits && !$size) { $this->size = $bits; $this->bits = $this->makeArray($bits); } else { $this->bits = $bits; $this->size = $size; } } private static function makeArray($size) { return []; } public function getSize() { return $this->size; } public function getSizeInBytes() { return ($this->size + 7) / 8; } /** * Sets bit i. * * @param i bit to set */ public function set($i) { $this->bits[(int)($i / 32)] |= 1 << ($i & 0x1F); $this->bits[(int)($i / 32)] = ($this->bits[(int)($i / 32)]); } /** * Flips bit i. * * @param i bit to set */ public function flip($i) { $this->bits[(int)($i / 32)] ^= 1 << ($i & 0x1F); $this->bits[(int)($i / 32)] = ($this->bits[(int)($i / 32)]); } /** * @param from first bit to check * * @return index of first bit that is set, starting from the given index, or size if none are set * at or beyond this given index * @see #getNextUnset(int) */ public function getNextSet($from) { if ($from >= $this->size) { return $this->size; } $bitsOffset = (int)($from / 32); $currentBits = (int)$this->bits[$bitsOffset]; // mask off lesser bits first $currentBits &= ~((1 << ($from & 0x1F)) - 1); while ($currentBits == 0) { if (++$bitsOffset == count($this->bits)) { return $this->size; } $currentBits = $this->bits[$bitsOffset]; } $result = ($bitsOffset * 32) + numberOfTrailingZeros($currentBits); //numberOfTrailingZeros return $result > $this->size ? $this->size : $result; } /** * @param from index to start looking for unset bit * * @return index of next unset bit, or {@code size} if none are unset until the end * @see #getNextSet(int) */ public function getNextUnset($from) { if ($from >= $this->size) { return $this->size; } $bitsOffset = (int)($from / 32); $currentBits = ~$this->bits[$bitsOffset]; // mask off lesser bits first $currentBits &= ~((1 << ($from & 0x1F)) - 1); while ($currentBits == 0) { if (++$bitsOffset == count($this->bits)) { return $this->size; } $currentBits = (~$this->bits[$bitsOffset]); } $result = ($bitsOffset * 32) + numberOfTrailingZeros($currentBits); return $result > $this->size ? $this->size : $result; } /** * Sets a block of 32 bits, starting at bit i. * * @param i first bit to set * @param newBits the new value of the next 32 bits. Note again that the least-significant bit * corresponds to bit i, the next-least-significant to i+1, and so on. */ public function setBulk($i, $newBits) { $this->bits[(int)($i / 32)] = $newBits; } /** * Sets a range of bits. * * @param start start of range, inclusive. * @param end end of range, exclusive */ public function setRange($start, $end) { if ($end < $start) { throw new \InvalidArgumentException(); } if ($end == $start) { return; } $end--; // will be easier to treat this as the last actually set bit -- inclusive $firstInt = (int)($start / 32); $lastInt = (int)($end / 32); for ($i = $firstInt; $i <= $lastInt; $i++) { $firstBit = $i > $firstInt ? 0 : $start & 0x1F; $lastBit = $i < $lastInt ? 31 : $end & 0x1F; $mask = 0; if ($firstBit == 0 && $lastBit == 31) { $mask = -1; } else { $mask = 0; for ($j = $firstBit; $j <= $lastBit; $j++) { $mask |= 1 << $j; } } $this->bits[$i] = ($this->bits[$i] | $mask); } } /** * Clears all bits (sets to false). */ public function clear() { $max = count($this->bits); for ($i = 0; $i < $max; $i++) { $this->bits[$i] = 0; } } /** * Efficient method to check if a range of bits is set, or not set. * * @param start start of range, inclusive. * @param end end of range, exclusive * @param value if true, checks that bits in range are set, otherwise checks that they are not set * * @return true iff all bits are set or not set in range, according to value argument * @throws InvalidArgumentException if end is less than or equal to start */ public function isRange($start, $end, $value) { if ($end < $start) { throw new \InvalidArgumentException(); } if ($end == $start) { return true; // empty range matches } $end--; // will be easier to treat this as the last actually set bit -- inclusive $firstInt = (int)($start / 32); $lastInt = (int)($end / 32); for ($i = $firstInt; $i <= $lastInt; $i++) { $firstBit = $i > $firstInt ? 0 : $start & 0x1F; $lastBit = $i < $lastInt ? 31 : $end & 0x1F; $mask = 0; if ($firstBit == 0 && $lastBit == 31) { $mask = -1; } else { $mask = 0; for ($j = $firstBit; $j <= $lastBit; $j++) { $mask = ($mask | (1 << $j)); } } // Return false if we're looking for 1s and the masked bits[i] isn't all 1s (that is, // equals the mask, or we're looking for 0s and the masked portion is not all 0s if (($this->bits[$i] & $mask) != ($value ? $mask : 0)) { return false; } } return true; } /** * Appends the least-significant bits, from value, in order from most-significant to * least-significant. For example, appending 6 bits from 0x000001E will append the bits * 0, 1, 1, 1, 1, 0 in that order. * * @param value {@code int} containing bits to append * @param numBits bits from value to append */ public function appendBits($value, $numBits) { if ($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 >> ($numBitsLeft - 1)) & 0x01) == 1); } } private function ensureCapacity($size) { if ($size > count($this->bits) * 32) { $newBits = $this->makeArray($size); $newBits = arraycopy($this->bits, 0, $newBits, 0, count($this->bits)); $this->bits = $newBits; } } public function appendBit($bit) { $this->ensureCapacity($this->size + 1); if ($bit) { $this->bits[(int)($this->size / 32)] |= 1 << ($this->size & 0x1F); } $this->size++; } public function appendBitArray($other) { $otherSize = $other->size; $this->ensureCapacity($this->size + $otherSize); for ($i = 0; $i < $otherSize; $i++) { $this->appendBit($other->get($i)); } } public function _xor($other) { if (count($this->bits) !== count($other->bits)) { throw new \InvalidArgumentException("Sizes don't match"); } $count = count($this->bits); for ($i = 0; $i < $count; $i++) { // The last byte could be incomplete (i.e. not have 8 bits in // it) but there is no problem since 0 XOR 0 == 0. $this->bits[$i] ^= $other->bits[$i]; } } /** * * @param bitOffset first bit to start writing * @param array array to write into. Bytes are written most-significant byte first. This is the opposite * of the internal representation, which is exposed by {@link #getBitArray()} * @param offset position in array to start writing * @param numBytes how many bytes to write */ public function toBytes($bitOffset, &$array, $offset, $numBytes) { for ($i = 0; $i < $numBytes; $i++) { $theByte = 0; for ($j = 0; $j < 8; $j++) { if ($this->get($bitOffset)) { $theByte |= 1 << (7 - $j); } $bitOffset++; } $array[(int)($offset + $i)] = $theByte; } } /** * @param $i ; bit to get * * @return true iff bit i is set */ public function get($i) { $key = (int)($i / 32); return ($this->bits[$key] & (1 << ($i & 0x1F))) != 0; } /** * @return array underlying array of ints. The first element holds the first 32 bits, and the least * significant bit is bit 0. */ public function getBitArray() { return $this->bits; } /** * Reverses all bits in the array. */ public function reverse() { $newBits = []; // reverse all int's first $len = (($this->size - 1) / 32); $oldBitsLen = $len + 1; for ($i = 0; $i < $oldBitsLen; $i++) { $x = $this->bits[$i];/* $x = (($x >> 1) & 0x55555555L) | (($x & 0x55555555L) << 1); $x = (($x >> 2) & 0x33333333L) | (($x & 0x33333333L) << 2); $x = (($x >> 4) & 0x0f0f0f0fL) | (($x & 0x0f0f0f0fL) << 4); $x = (($x >> 8) & 0x00ff00ffL) | (($x & 0x00ff00ffL) << 8); $x = (($x >> 16) & 0x0000ffffL) | (($x & 0x0000ffffL) << 16);*/ $x = (($x >> 1) & 0x55555555) | (($x & 0x55555555) << 1); $x = (($x >> 2) & 0x33333333) | (($x & 0x33333333) << 2); $x = (($x >> 4) & 0x0f0f0f0f) | (($x & 0x0f0f0f0f) << 4); $x = (($x >> 8) & 0x00ff00ff) | (($x & 0x00ff00ff) << 8); $x = (($x >> 16) & 0x0000ffff) | (($x & 0x0000ffff) << 16); $newBits[(int)$len - $i] = (int)$x; } // now correct the int's if the bit size isn't a multiple of 32 if ($this->size != $oldBitsLen * 32) { $leftOffset = $oldBitsLen * 32 - $this->size; $mask = 1; for ($i = 0; $i < 31 - $leftOffset; $i++) { $mask = ($mask << 1) | 1; } $currentInt = ($newBits[0] >> $leftOffset) & $mask; for ($i = 1; $i < $oldBitsLen; $i++) { $nextInt = $newBits[$i]; $currentInt |= $nextInt << (32 - $leftOffset); $newBits[(int)($i) - 1] = $currentInt; $currentInt = ($nextInt >> $leftOffset) & $mask; } $newBits[(int)($oldBitsLen) - 1] = $currentInt; } // $bits = $newBits; } public function equals($o) { if (!($o instanceof BitArray)) { return false; } $other = $o; return $this->size == $other->size && $this->bits === $other->bits; } public function hashCode() { return 31 * $this->size + hashCode($this->bits); } public function toString() { $result = ''; for ($i = 0; $i < $this->size; $i++) { if (($i & 0x07) == 0) { $result .= ' '; } $result .= ($this->get($i) ? 'X' : '.'); } return (string)$result; } public function _clone() { return new BitArray($this->bits, $this->size); } }