includes/utils/Cdb.php

   1 <?php
   2 /**
   3  * Native CDB file reader and writer.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * Read from a CDB file.
  25  * Native and pure PHP implementations are provided.
  26  * http://cr.yp.to/cdb.html
  27  */
  28 abstract class CdbReader {
  29         /**
  30          * Open a file and return a subclass instance
  31          *
  32          * @param $fileName string
  33          *
  34          * @return CdbReader
  35          */
  36         public static function open( $fileName ) {
  37                 if ( self::haveExtension() ) {
  38                         return new CdbReader_DBA( $fileName );
  39                 } else {
  40                         wfDebug( "Warning: no dba extension found, using emulation.\n" );
  41
  42                         return new CdbReader_PHP( $fileName );
  43                 }
  44         }
  45
  46         /**
  47          * Returns true if the native extension is available
  48          *
  49          * @return bool
  50          */
  51         public static function haveExtension() {
  52                 if ( !function_exists( 'dba_handlers' ) ) {
  53                         return false;
  54                 }
  55                 $handlers = dba_handlers();
  56                 if ( !in_array( 'cdb', $handlers ) || !in_array( 'cdb_make', $handlers ) ) {
  57                         return false;
  58                 }
  59
  60                 return true;
  61         }
  62
  63         /**
  64          * Construct the object and open the file
  65          */
  66         abstract function __construct( $fileName );
  67
  68         /**
  69          * Close the file. Optional, you can just let the variable go out of scope.
  70          */
  71         abstract function close();
  72
  73         /**
  74          * Get a value with a given key. Only string values are supported.
  75          *
  76          * @param $key string
  77          */
  78         abstract public function get( $key );
  79 }
  80
  81 /**
  82  * Write to a CDB file.
  83  * Native and pure PHP implementations are provided.
  84  */
  85 abstract class CdbWriter {
  86         /**
  87          * Open a writer and return a subclass instance.
  88          * The user must have write access to the directory, for temporary file creation.
  89          *
  90          * @param $fileName string
  91          *
  92          * @return CdbWriter_DBA|CdbWriter_PHP
  93          */
  94         public static function open( $fileName ) {
  95                 if ( CdbReader::haveExtension() ) {
  96                         return new CdbWriter_DBA( $fileName );
  97                 } else {
  98                         wfDebug( "Warning: no dba extension found, using emulation.\n" );
  99
 100                         return new CdbWriter_PHP( $fileName );
 101                 }
 102         }
 103
 104         /**
 105          * Create the object and open the file
 106          *
 107          * @param $fileName string
 108          */
 109         abstract function __construct( $fileName );
 110
 111         /**
 112          * Set a key to a given value. The value will be converted to string.
 113          * @param $key string
 114          * @param $value string
 115          */
 116         abstract public function set( $key, $value );
 117
 118         /**
 119          * Close the writer object. You should call this function before the object
 120          * goes out of scope, to write out the final hashtables.
 121          */
 122         abstract public function close();
 123 }
 124
 125 /**
 126  * Reader class which uses the DBA extension
 127  */
 128 class CdbReader_DBA {
 129         var $handle;
 130
 131         function __construct( $fileName ) {
 132                 $this->handle = dba_open( $fileName, 'r-', 'cdb' );
 133                 if ( !$this->handle ) {
 134                         throw new MWException( 'Unable to open CDB file "' . $fileName . '"' );
 135                 }
 136         }
 137
 138         function close() {
 139                 if ( isset( $this->handle ) ) {
 140                         dba_close( $this->handle );
 141                 }
 142                 unset( $this->handle );
 143         }
 144
 145         function get( $key ) {
 146                 return dba_fetch( $key, $this->handle );
 147         }
 148 }
 149
 150 /**
 151  * Writer class which uses the DBA extension
 152  */
 153 class CdbWriter_DBA {
 154         var $handle, $realFileName, $tmpFileName;
 155
 156         function __construct( $fileName ) {
 157                 $this->realFileName = $fileName;
 158                 $this->tmpFileName = $fileName . '.tmp.' . mt_rand( 0, 0x7fffffff );
 159                 $this->handle = dba_open( $this->tmpFileName, 'n', 'cdb_make' );
 160                 if ( !$this->handle ) {
 161                         throw new MWException( 'Unable to open CDB file for write "' . $fileName . '"' );
 162                 }
 163         }
 164
 165         function set( $key, $value ) {
 166                 return dba_insert( $key, $value, $this->handle );
 167         }
 168
 169         function close() {
 170                 if ( isset( $this->handle ) ) {
 171                         dba_close( $this->handle );
 172                 }
 173                 if ( wfIsWindows() ) {
 174                         unlink( $this->realFileName );
 175                 }
 176                 if ( !rename( $this->tmpFileName, $this->realFileName ) ) {
 177                         throw new MWException( 'Unable to move the new CDB file into place.' );
 178                 }
 179                 unset( $this->handle );
 180         }
 181
 182         function __destruct() {
 183                 if ( isset( $this->handle ) ) {
 184                         $this->close();
 185                 }
 186         }
 187 }