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<?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. Changes are:
* * Error returns replaced with exceptions
* * Exception thrown if sizes or offsets are between 2GB and 4GB
* * Some variables renamed
*
* 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 {
/** The filename */
protected $fileName;
/* number of hash slots searched under this key */
protected $loop;
/* initialized if loop is nonzero */
protected $khash;
/* initialized if loop is nonzero */
protected $kpos;
/* initialized if loop is nonzero */
protected $hpos;
/* initialized if loop is nonzero */
protected $hslots;
/* initialized if findNext() returns true */
protected $dpos;
/* initialized if cdb_findnext() returns 1 */
protected $dlen;
/**
* @param string $fileName
* @throws Exception
*/
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->findStart();
}
public function close() {
if ( isset( $this->handle ) ) {
fclose( $this->handle );
}
unset( $this->handle );
}
/**
* @param mixed $key
* @return bool|string
*/
public function get( $key ) {
// strval is required
if ( $this->find( strval( $key ) ) ) {
return $this->read( $this->dlen, $this->dpos );
}
return false;
}
/**
* @param string $key
* @param int $pos
* @return bool
*/
protected function match( $key, $pos ) {
$buf = $this->read( strlen( $key ), $pos );
return $buf === $key;
}
protected function findStart() {
$this->loop = 0;
}
/**
* @throws Exception
* @param int $length
* @param int $pos
* @return string
*/
protected function read( $length, $pos ) {
if ( fseek( $this->handle, $pos ) == -1 ) {
// This can easily happen if the internal pointers are incorrect
throw new Exception(
'Seek failed, file "' . $this->fileName . '" may be corrupted.' );
}
if ( $length == 0 ) {
return '';
}
$buf = fread( $this->handle, $length );
if ( $buf === false || strlen( $buf ) !== $length ) {
throw new Exception(
'Read from CDB file failed, file "' . $this->fileName . '" may be corrupted.' );
}
return $buf;
}
/**
* Unpack an unsigned integer and throw an exception if it needs more than 31 bits
* @param string $s
* @throws Exception
* @return mixed
*/
protected function unpack31( $s ) {
$data = unpack( 'V', $s );
if ( $data[1] > 0x7fffffff ) {
throw new Exception(
'Error in CDB file "' . $this->fileName . '", integer too big.' );
}
return $data[1];
}
/**
* Unpack a 32-bit signed integer
* @param string $s
* @return int
*/
protected function unpackSigned( $s ) {
$data = unpack( 'va/vb', $s );
return $data['a'] | ( $data['b'] << 16 );
}
/**
* @param string $key
* @return bool
*/
protected function findNext( $key ) {
if ( !$this->loop ) {
$u = Util::hash( $key );
$buf = $this->read( 8, ( $u << 3 ) & 2047 );
$this->hslots = $this->unpack31( substr( $buf, 4 ) );
if ( !$this->hslots ) {
return false;
}
$this->hpos = $this->unpack31( substr( $buf, 0, 4 ) );
$this->khash = $u;
$u = Util::unsignedShiftRight( $u, 8 );
$u = Util::unsignedMod( $u, $this->hslots );
$u <<= 3;
$this->kpos = $this->hpos + $u;
}
while ( $this->loop < $this->hslots ) {
$buf = $this->read( 8, $this->kpos );
$pos = $this->unpack31( substr( $buf, 4 ) );
if ( !$pos ) {
return false;
}
$this->loop += 1;
$this->kpos += 8;
if ( $this->kpos == $this->hpos + ( $this->hslots << 3 ) ) {
$this->kpos = $this->hpos;
}
$u = $this->unpackSigned( substr( $buf, 0, 4 ) );
if ( $u === $this->khash ) {
$buf = $this->read( 8, $pos );
$keyLen = $this->unpack31( substr( $buf, 0, 4 ) );
if ( $keyLen == strlen( $key ) && $this->match( $key, $pos + 8 ) ) {
// Found
$this->dlen = $this->unpack31( substr( $buf, 4 ) );
$this->dpos = $pos + 8 + $keyLen;
return true;
}
}
}
return false;
}
/**
* @param mixed $key
* @return bool
*/
protected function find( $key ) {
$this->findStart();
return $this->findNext( $key );
}
}
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