includes/libs/cdb/CdbWriterPHP.php

   1 <?php
   2 /**
   3  * This is a port of D.J. Bernstein's CDB to PHP. It's based on the copy that
   4  * appears in PHP 5.3. Changes are:
   5  *    * Error returns replaced with exceptions
   6  *    * Exception thrown if sizes or offsets are between 2GB and 4GB
   7  *    * Some variables renamed
   8  *
   9  * This program is free software; you can redistribute it and/or modify
  10  * it under the terms of the GNU General Public License as published by
  11  * the Free Software Foundation; either version 2 of the License, or
  12  * (at your option) any later version.
  13  *
  14  * This program is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  17  * GNU General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write to the Free Software Foundation, Inc.,
  21  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  22  * http://www.gnu.org/copyleft/gpl.html
  23  *
  24  * @file
  25  */
  26
  27 /**
  28  * CDB writer class
  29  */
  30 class CdbWriterPHP extends CdbWriter {
  31         protected $hplist;
  32
  33         protected $numentries;
  34
  35         protected $pos;
  36
  37         /**
  38          * @param string $fileName
  39          */
  40         public function __construct( $fileName ) {
  41                 $this->realFileName = $fileName;
  42                 $this->tmpFileName = $fileName . '.tmp.' . mt_rand( 0, 0x7fffffff );
  43                 $this->handle = fopen( $this->tmpFileName, 'wb' );
  44                 if ( !$this->handle ) {
  45                         $this->throwException(
  46                                 'Unable to open CDB file "' . $this->tmpFileName . '" for write.' );
  47                 }
  48                 $this->hplist = array();
  49                 $this->numentries = 0;
  50                 $this->pos = 2048; // leaving space for the pointer array, 256 * 8
  51                 if ( fseek( $this->handle, $this->pos ) == -1 ) {
  52                         $this->throwException( 'fseek failed in file "' . $this->tmpFileName . '".' );
  53                 }
  54         }
  55
  56         /**
  57          * @param string $key
  58          * @param string $value
  59          */
  60         public function set( $key, $value ) {
  61                 if ( strval( $key ) === '' ) {
  62                         // DBA cross-check hack
  63                         return;
  64                 }
  65                 $this->addbegin( strlen( $key ), strlen( $value ) );
  66                 $this->write( $key );
  67                 $this->write( $value );
  68                 $this->addend( strlen( $key ), strlen( $value ), CdbFunctions::hash( $key ) );
  69         }
  70
  71         /**
  72          * @throws CdbException
  73          */
  74         public function close() {
  75                 $this->finish();
  76                 if ( isset( $this->handle ) ) {
  77                         fclose( $this->handle );
  78                 }
  79                 if ( $this->isWindows() && file_exists( $this->realFileName ) ) {
  80                         unlink( $this->realFileName );
  81                 }
  82                 if ( !rename( $this->tmpFileName, $this->realFileName ) ) {
  83                         $this->throwException( 'Unable to move the new CDB file into place.' );
  84                 }
  85                 unset( $this->handle );
  86         }
  87
  88         /**
  89          * @throws CdbException
  90          * @param string $buf
  91          */
  92         protected function write( $buf ) {
  93                 $len = fwrite( $this->handle, $buf );
  94                 if ( $len !== strlen( $buf ) ) {
  95                         $this->throwException( 'Error writing to CDB file "' . $this->tmpFileName . '".' );
  96                 }
  97         }
  98
  99         /**
 100          * @throws CdbException
 101          * @param int $len
 102          */
 103         protected function posplus( $len ) {
 104                 $newpos = $this->pos + $len;
 105                 if ( $newpos > 0x7fffffff ) {
 106                         $this->throwException(
 107                                 'A value in the CDB file "' . $this->tmpFileName . '" is too large.' );
 108                 }
 109                 $this->pos = $newpos;
 110         }
 111
 112         /**
 113          * @param int $keylen
 114          * @param int $datalen
 115          * @param int $h
 116          */
 117         protected function addend( $keylen, $datalen, $h ) {
 118                 $this->hplist[] = array(
 119                         'h' => $h,
 120                         'p' => $this->pos
 121                 );
 122
 123                 $this->numentries++;
 124                 $this->posplus( 8 );
 125                 $this->posplus( $keylen );
 126                 $this->posplus( $datalen );
 127         }
 128
 129         /**
 130          * @throws CdbException
 131          * @param int $keylen
 132          * @param int $datalen
 133          */
 134         protected function addbegin( $keylen, $datalen ) {
 135                 if ( $keylen > 0x7fffffff ) {
 136                         $this->throwException( 'Key length too long in file "' . $this->tmpFileName . '".' );
 137                 }
 138                 if ( $datalen > 0x7fffffff ) {
 139                         $this->throwException( 'Data length too long in file "' . $this->tmpFileName . '".' );
 140                 }
 141                 $buf = pack( 'VV', $keylen, $datalen );
 142                 $this->write( $buf );
 143         }
 144
 145         /**
 146          * @throws CdbException
 147          */
 148         protected function finish() {
 149                 // Hack for DBA cross-check
 150                 $this->hplist = array_reverse( $this->hplist );
 151
 152                 // Calculate the number of items that will be in each hashtable
 153                 $counts = array_fill( 0, 256, 0 );
 154                 foreach ( $this->hplist as $item ) {
 155                         ++$counts[255 & $item['h']];
 156                 }
 157
 158                 // Fill in $starts with the *end* indexes
 159                 $starts = array();
 160                 $pos = 0;
 161                 for ( $i = 0; $i < 256; ++$i ) {
 162                         $pos += $counts[$i];
 163                         $starts[$i] = $pos;
 164                 }
 165
 166                 // Excessively clever and indulgent code to simultaneously fill $packedTables
 167                 // with the packed hashtables, and adjust the elements of $starts
 168                 // to actually point to the starts instead of the ends.
 169                 $packedTables = array_fill( 0, $this->numentries, false );
 170                 foreach ( $this->hplist as $item ) {
 171                         $packedTables[--$starts[255 & $item['h']]] = $item;
 172                 }
 173
 174                 $final = '';
 175                 for ( $i = 0; $i < 256; ++$i ) {
 176                         $count = $counts[$i];
 177
 178                         // The size of the hashtable will be double the item count.
 179                         // The rest of the slots will be empty.
 180                         $len = $count + $count;
 181                         $final .= pack( 'VV', $this->pos, $len );
 182
 183                         $hashtable = array();
 184                         for ( $u = 0; $u < $len; ++$u ) {
 185                                 $hashtable[$u] = array( 'h' => 0, 'p' => 0 );
 186                         }
 187
 188                         // Fill the hashtable, using the next empty slot if the hashed slot
 189                         // is taken.
 190                         for ( $u = 0; $u < $count; ++$u ) {
 191                                 $hp = $packedTables[$starts[$i] + $u];
 192                                 $where = CdbFunctions::unsignedMod(
 193                                         CdbFunctions::unsignedShiftRight( $hp['h'], 8 ), $len );
 194                                 while ( $hashtable[$where]['p'] ) {
 195                                         if ( ++$where == $len ) {
 196                                                 $where = 0;
 197                                         }
 198                                 }
 199                                 $hashtable[$where] = $hp;
 200                         }
 201
 202                         // Write the hashtable
 203                         for ( $u = 0; $u < $len; ++$u ) {
 204                                 $buf = pack( 'vvV',
 205                                         $hashtable[$u]['h'] & 0xffff,
 206                                         CdbFunctions::unsignedShiftRight( $hashtable[$u]['h'], 16 ),
 207                                         $hashtable[$u]['p'] );
 208                                 $this->write( $buf );
 209                                 $this->posplus( 8 );
 210                         }
 211                 }
 212
 213                 // Write the pointer array at the start of the file
 214                 rewind( $this->handle );
 215                 if ( ftell( $this->handle ) != 0 ) {
 216                         $this->throwException( 'Error rewinding to start of file "' . $this->tmpFileName . '".' );
 217                 }
 218                 $this->write( $final );
 219         }
 220
 221         /**
 222          * Clean up the temp file and throw an exception
 223          *
 224          * @param string $msg
 225          * @throws CdbException
 226          */
 227         protected function throwException( $msg ) {
 228                 if ( $this->handle ) {
 229                         fclose( $this->handle );
 230                         unlink( $this->tmpFileName );
 231                 }
 232                 throw new CdbException( $msg );
 233         }
 234 }