includes/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                         return new CdbReader_PHP( $fileName );
  42                 }
  43         }
  44
  45         /**
  46          * Returns true if the native extension is available
  47          *
  48          * @return bool
  49          */
  50         public static function haveExtension() {
  51                 if ( !function_exists( 'dba_handlers' ) ) {
  52                         return false;
  53                 }
  54                 $handlers = dba_handlers();
  55                 if ( !in_array( 'cdb', $handlers ) || !in_array( 'cdb_make', $handlers ) ) {
  56                         return false;
  57                 }
  58                 return true;
  59         }
  60
  61         /**
  62          * Construct the object and open the file
  63          */
  64         abstract function __construct( $fileName );
  65
  66         /**
  67          * Close the file. Optional, you can just let the variable go out of scope.
  68          */
  69         abstract function close();
  70
  71         /**
  72          * Get a value with a given key. Only string values are supported.
  73          *
  74          * @param $key string
  75          */
  76         abstract public function get( $key );
  77 }
  78
  79 /**
  80  * Write to a CDB file.
  81  * Native and pure PHP implementations are provided.
  82  */
  83 abstract class CdbWriter {
  84         /**
  85          * Open a writer and return a subclass instance.
  86          * The user must have write access to the directory, for temporary file creation.
  87          *
  88          * @param $fileName string
  89          *
  90          * @return CdbWriter_DBA|CdbWriter_PHP
  91          */
  92         public static function open( $fileName ) {
  93                 if ( CdbReader::haveExtension() ) {
  94                         return new CdbWriter_DBA( $fileName );
  95                 } else {
  96                         wfDebug( "Warning: no dba extension found, using emulation.\n" );
  97                         return new CdbWriter_PHP( $fileName );
  98                 }
  99         }
 100
 101         /**
 102          * Create the object and open the file
 103          *
 104          * @param $fileName string
 105          */
 106         abstract function __construct( $fileName );
 107
 108         /**
 109          * Set a key to a given value. The value will be converted to string.
 110          * @param $key string
 111          * @param $value string
 112          */
 113         abstract public function set( $key, $value );
 114
 115         /**
 116          * Close the writer object. You should call this function before the object
 117          * goes out of scope, to write out the final hashtables.
 118          */
 119         abstract public function close();
 120 }
 121
 122 /**
 123  * Reader class which uses the DBA extension
 124  */
 125 class CdbReader_DBA {
 126         var $handle;
 127
 128         function __construct( $fileName ) {
 129                 $this->handle = dba_open( $fileName, 'r-', 'cdb' );
 130                 if ( !$this->handle ) {
 131                         throw new MWException( 'Unable to open CDB file "' . $fileName . '"' );
 132                 }
 133         }
 134
 135         function close() {
 136                 if ( isset( $this->handle ) ) {
 137                         dba_close( $this->handle );
 138                 }
 139                 unset( $this->handle );
 140         }
 141
 142         function get( $key ) {
 143                 return dba_fetch( $key, $this->handle );
 144         }
 145 }
 146
 147 /**
 148  * Writer class which uses the DBA extension
 149  */
 150 class CdbWriter_DBA {
 151         var $handle, $realFileName, $tmpFileName;
 152
 153         function __construct( $fileName ) {
 154                 $this->realFileName = $fileName;
 155                 $this->tmpFileName = $fileName . '.tmp.' . mt_rand( 0, 0x7fffffff );
 156                 $this->handle = dba_open( $this->tmpFileName, 'n', 'cdb_make' );
 157                 if ( !$this->handle ) {
 158                         throw new MWException( 'Unable to open CDB file for write "' . $fileName . '"' );
 159                 }
 160         }
 161
 162         function set( $key, $value ) {
 163                 return dba_insert( $key, $value, $this->handle );
 164         }
 165
 166         function close() {
 167                 if ( isset( $this->handle ) ) {
 168                         dba_close( $this->handle );
 169                 }
 170                 if ( wfIsWindows() ) {
 171                         unlink( $this->realFileName );
 172                 }
 173                 if ( !rename( $this->tmpFileName, $this->realFileName ) ) {
 174                         throw new MWException( 'Unable to move the new CDB file into place.' );
 175                 }
 176                 unset( $this->handle );
 177         }
 178
 179         function __destruct() {
 180                 if ( isset( $this->handle ) ) {
 181                         $this->close();
 182                 }
 183         }
 184 }