Current File : //www/varak.net/wiki.varak.net/vendor/wikimedia/cdb/src/Reader/PHP.php
<?php
namespace Cdb\Reader;
use Cdb\Exception;
use Cdb\Reader;
use Cdb\Util;
/**
* This is a port of D.J. Bernstein's CDB to PHP. It's based on the copy that
* appears in PHP 5.3.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
* http://www.gnu.org/copyleft/gpl.html
*
* @file
*/
/**
* CDB reader class
*/
class PHP extends Reader {
/** @var string The file name of the CDB file. **/
protected $fileName;
/** @var string First 2048b of CDB file, containing pointers to hash table. **/
protected $index;
/** @var int Offset in file where value of found key starts. **/
protected $dataPos;
/** @var int Byte length of found key's value. **/
protected $dataLen;
/** @var int File position indicator when iterating over keys. **/
protected $keyIterPos = 2048;
/** @var int Offset in file where hash tables start. **/
protected $keyIterStop;
/** @var string Read buffer for CDB file. **/
protected $buf;
/** @var int File offset where read buffer starts. **/
protected $bufStart;
/** @var int File handle position indicator **/
protected $filePos = 2048;
/**
* Constructor.
*
* @param string $fileName
* @throws Exception If CDB file cannot be opened or if it contains fewer
* than 2048 bytes of data.
*/
public function __construct( $fileName ) {
$this->fileName = $fileName;
$this->handle = fopen( $fileName, 'rb' );
if ( !$this->handle ) {
throw new Exception( 'Unable to open CDB file "' . $this->fileName . '".' );
}
$this->index = fread( $this->handle, 2048 );
if ( strlen( $this->index ) !== 2048 ) {
throw new Exception( 'CDB file contains fewer than 2048 bytes of data.' );
}
}
/**
* Close the handle on the CDB file.
*/
public function close() {
if ( isset( $this->handle ) ) {
fclose( $this->handle );
}
unset( $this->handle );
}
/**
* Get the value of a key.
*
* @param mixed $key
* @return bool|string The key's value or false if not found.
*/
public function get( $key ) {
// strval is required
if ( $this->find( strval( $key ) ) ) {
return $this->read( $this->dataPos, $this->dataLen );
}
return false;
}
/**
* Read data from the CDB file.
*
* @throws Exception When attempting to read past the end of the file.
* @param int $start Start reading from this position.
* @param int $len Number of bytes to read.
* @return string Read data.
*/
protected function read( $start, $len ) {
$end = $start + $len;
// The first 2048 bytes are the lookup table, which is read into
// memory on initialization.
if ( $end <= 2048 ) {
return substr( $this->index, $start, $len );
}
// Read data from the internal buffer first.
$bytes = '';
if ( $this->buf && $start >= $this->bufStart ) {
$bytes .= substr( $this->buf, $start - $this->bufStart, $len );
$bytesRead = strlen( $bytes );
$len -= $bytesRead;
$start += $bytesRead;
} else {
$bytesRead = 0;
}
if ( !$len ) {
return $bytes;
}
// Many reads are sequential, so the file position indicator may
// already be in the right place, in which case we can avoid the
// call to fseek().
if ( $start !== $this->filePos ) {
if ( fseek( $this->handle, $start ) === -1 ) {
// This can easily happen if the internal pointers are incorrect
throw new Exception(
'Seek failed, file "' . $this->fileName . '" may be corrupted.' );
}
}
$buf = fread( $this->handle, max( $len, 1024 ) );
if ( $buf === false ) {
$buf = '';
}
$bytes .= substr( $buf, 0, $len );
if ( strlen( $bytes ) !== $len + $bytesRead ) {
throw new Exception(
'Read from CDB file failed, file "' . $this->fileName . '" may be corrupted.' );
}
$this->filePos = $end;
$this->bufStart = $start;
$this->buf = $buf;
return $bytes;
}
/**
* Unpack an unsigned integer and throw an exception if it needs more than 31 bits.
*
* @param int $pos Position to read from.
* @throws Exception When the integer cannot be represented in 31 bits.
* @return int
*/
protected function readInt31( $pos = 0 ) {
$uint31 = $this->readInt32( $pos );
if ( $uint31 > 0x7fffffff ) {
throw new Exception(
'Error in CDB file "' . $this->fileName . '", integer too big.' );
}
return $uint31;
}
/**
* Unpack a 32-bit integer.
*
* @param int $pos
* @return int
*/
protected function readInt32( $pos = 0 ) {
static $lookups;
if ( !$lookups ) {
$lookups = array();
for ( $i = 1; $i < 256; $i++ ) {
$lookups[ chr( $i ) ] = $i;
}
}
$buf = $this->read( $pos, 4 );
$rv = 0;
if ( $buf[0] !== "\x0" ) {
$rv = $lookups[ $buf[0] ];
}
if ( $buf[1] !== "\x0" ) {
$rv |= ( $lookups[ $buf[1] ] << 8 );
}
if ( $buf[2] !== "\x0" ) {
$rv |= ( $lookups[ $buf[2] ] << 16 );
}
if ( $buf[3] !== "\x0" ) {
$rv |= ( $lookups[ $buf[3] ] << 24 );
}
return $rv;
}
/**
* Search the CDB file for a key.
*
* Sets `dataLen` and `dataPos` properties if successful.
*
* @param string $key
* @return bool Whether the key was found.
*/
protected function find( $key ) {
$keyLen = strlen( $key );
$u = Util::hash( $key );
$upos = ( $u << 3 ) & 2047;
$hashSlots = $this->readInt31( $upos + 4 );
if ( !$hashSlots ) {
return false;
}
$hashPos = $this->readInt31( $upos );
$keyHash = $u;
$u = Util::unsignedShiftRight( $u, 8 );
$u = Util::unsignedMod( $u, $hashSlots );
$u <<= 3;
$keyPos = $hashPos + $u;
for ( $i = 0; $i < $hashSlots; $i++ ) {
$hash = $this->readInt32( $keyPos );
$pos = $this->readInt31( $keyPos + 4 );
if ( !$pos ) {
return false;
}
$keyPos += 8;
if ( $keyPos == $hashPos + ( $hashSlots << 3 ) ) {
$keyPos = $hashPos;
}
if ( $hash === $keyHash ) {
if ( $keyLen === $this->readInt31( $pos ) ) {
$dataLen = $this->readInt31( $pos + 4 );
$dataPos = $pos + 8 + $keyLen;
$foundKey = $this->read( $pos + 8, $keyLen );
if ( $foundKey === $key ) {
// Found
$this->dataLen = $dataLen;
$this->dataPos = $dataPos;
return true;
}
}
}
}
return false;
}
/**
* Check if a key exists in the CDB file.
*
* @param string $key
* @return bool Whether the key exists.
*/
public function exists( $key ) {
return $this->find( strval( $key ) );
}
/**
* Get the first key from the CDB file and reset the key iterator.
*
* @return string|bool Key, or false if no keys in file.
*/
public function firstkey() {
$this->keyIterPos = 4;
if ( !$this->keyIterStop ) {
$pos = INF;
for ( $i = 0; $i < 2048; $i+= 8 ) {
$pos = min( $this->readInt31( $i ), $pos );
}
$this->keyIterStop = $pos;
}
$this->keyIterPos = 2048;
return $this->nextkey();
}
/**
* Get the next key from the CDB file.
*
* @return string|bool Key, or false if no more keys.
*/
public function nextkey() {
if ( $this->keyIterPos >= $this->keyIterStop ) {
return false;
}
$keyLen = $this->readInt31( $this->keyIterPos );
$dataLen = $this->readInt31( $this->keyIterPos + 4 );
$key = $this->read( $this->keyIterPos + 8, $keyLen );
$this->keyIterPos += 8 + $keyLen + $dataLen;
return $key;
}
}
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