includes/HistoryBlob.php

   1 <?php
   2 /**
   3  *
   4  */
   5
   6 /**
   7  * Pure virtual parent
   8  */
   9 class HistoryBlob
  10 {
  11         /**
  12          * setMeta and getMeta currently aren't used for anything, I just thought
  13          * they might be useful in the future.
  14          * @param $meta String: a single string.
  15          */
  16         function setMeta( $meta ) {}
  17
  18         /**
  19          * setMeta and getMeta currently aren't used for anything, I just thought
  20          * they might be useful in the future.
  21          * Gets the meta-value
  22          */
  23         function getMeta() {}
  24
  25         /**
  26          * Adds an item of text, returns a stub object which points to the item.
  27          * You must call setLocation() on the stub object before storing it to the
  28          * database
  29          */
  30         function addItem() {}
  31
  32         /**
  33          * Get item by hash
  34          */
  35         function getItem( $hash ) {}
  36
  37         # Set the "default text"
  38         # This concept is an odd property of the current DB schema, whereby each text item has a revision
  39         # associated with it. The default text is the text of the associated revision. There may, however,
  40         # be other revisions in the same object
  41         function setText() {}
  42
  43         /**
  44          * Get default text. This is called from Revision::getRevisionText()
  45          */
  46         function getText() {}
  47 }
  48
  49 /**
  50  * The real object
  51  */
  52 class ConcatenatedGzipHistoryBlob extends HistoryBlob
  53 {
  54         /* private */ var $mVersion = 0, $mCompressed = false, $mItems = array(), $mDefaultHash = '';
  55         /* private */ var $mFast = 0, $mSize = 0;
  56
  57         function ConcatenatedGzipHistoryBlob() {
  58                 if ( !function_exists( 'gzdeflate' ) ) {
  59                         throw new MWException( "Need zlib support to read or write this kind of history object (ConcatenatedGzipHistoryBlob)\n" );
  60                 }
  61         }
  62
  63         /** @todo document */
  64         function setMeta( $metaData ) {
  65                 $this->uncompress();
  66                 $this->mItems['meta'] = $metaData;
  67         }
  68
  69         /** @todo document */
  70         function getMeta() {
  71                 $this->uncompress();
  72                 return $this->mItems['meta'];
  73         }
  74
  75         /** @todo document */
  76         function addItem( $text ) {
  77                 $this->uncompress();
  78                 $hash = md5( $text );
  79                 $this->mItems[$hash] = $text;
  80                 $this->mSize += strlen( $text );
  81
  82                 $stub = new HistoryBlobStub( $hash );
  83                 return $stub;
  84         }
  85
  86         /** @todo document */
  87         function getItem( $hash ) {
  88                 $this->uncompress();
  89                 if ( array_key_exists( $hash, $this->mItems ) ) {
  90                         return $this->mItems[$hash];
  91                 } else {
  92                         return false;
  93                 }
  94         }
  95
  96         /** @todo document */
  97         function removeItem( $hash ) {
  98                 $this->mSize -= strlen( $this->mItems[$hash] );
  99                 unset( $this->mItems[$hash] );
 100         }
 101
 102         /** @todo document */
 103         function compress() {
 104                 if ( !$this->mCompressed  ) {
 105                         $this->mItems = gzdeflate( serialize( $this->mItems ) );
 106                         $this->mCompressed = true;
 107                 }
 108         }
 109
 110         /** @todo document */
 111         function uncompress() {
 112                 if ( $this->mCompressed ) {
 113                         $this->mItems = unserialize( gzinflate( $this->mItems ) );
 114                         $this->mCompressed = false;
 115                 }
 116         }
 117
 118         /** @todo document */
 119         function getText() {
 120                 $this->uncompress();
 121                 return $this->getItem( $this->mDefaultHash );
 122         }
 123
 124         /** @todo document */
 125         function setText( $text ) {
 126                 $this->uncompress();
 127                 $stub = $this->addItem( $text );
 128                 $this->mDefaultHash = $stub->mHash;
 129         }
 130
 131         /** @todo document */
 132         function __sleep() {
 133                 $this->compress();
 134                 return array( 'mVersion', 'mCompressed', 'mItems', 'mDefaultHash' );
 135         }
 136
 137         /** @todo document */
 138         function __wakeup() {
 139                 $this->uncompress();
 140         }
 141
 142         /**
 143          * Determines if this object is happy
 144          */
 145         function isHappy( $maxFactor, $factorThreshold ) {
 146                 if ( count( $this->mItems ) == 0 ) {
 147                         return true;
 148                 }
 149                 if ( !$this->mFast ) {
 150                         $this->uncompress();
 151                         $record = serialize( $this->mItems );
 152                         $size = strlen( $record );
 153                         $avgUncompressed = $size / count( $this->mItems );
 154                         $compressed = strlen( gzdeflate( $record ) );
 155
 156                         if ( $compressed < $factorThreshold * 1024 ) {
 157                                 return true;
 158                         } else {
 159                                 return $avgUncompressed * $maxFactor < $compressed;
 160                         }
 161                 } else {
 162                         return count( $this->mItems ) <= 10;
 163                 }
 164         }
 165 }
 166
 167
 168 /**
 169  * One-step cache variable to hold base blobs; operations that
 170  * pull multiple revisions may often pull multiple times from
 171  * the same blob. By keeping the last-used one open, we avoid
 172  * redundant unserialization and decompression overhead.
 173  */
 174 global $wgBlobCache;
 175 $wgBlobCache = array();
 176
 177
 178 /**
 179  */
 180 class HistoryBlobStub {
 181         var $mOldId, $mHash, $mRef;
 182
 183         /** @todo document */
 184         function HistoryBlobStub( $hash = '', $oldid = 0 ) {
 185                 $this->mHash = $hash;
 186         }
 187
 188         /**
 189          * Sets the location (old_id) of the main object to which this object
 190          * points
 191          */
 192         function setLocation( $id ) {
 193                 $this->mOldId = $id;
 194         }
 195
 196       /**
 197        * Sets the location (old_id) of the referring object
 198        */
 199         function setReferrer( $id ) {
 200                 $this->mRef = $id;
 201         }
 202
 203       /**
 204        * Gets the location of the referring object
 205        */
 206         function getReferrer() {
 207                 return $this->mRef;
 208         }
 209
 210         /** @todo document */
 211         function getText() {
 212                 $fname = 'HistoryBlob::getText';
 213                 global $wgBlobCache;
 214                 if( isset( $wgBlobCache[$this->mOldId] ) ) {
 215                         $obj = $wgBlobCache[$this->mOldId];
 216                 } else {
 217                         $dbr =& wfGetDB( DB_SLAVE );
 218                         $row = $dbr->selectRow( 'text', array( 'old_flags', 'old_text' ), array( 'old_id' => $this->mOldId ) );
 219                         if( !$row ) {
 220                                 return false;
 221                         }
 222                         $flags = explode( ',', $row->old_flags );
 223                         if( in_array( 'external', $flags ) ) {
 224                                 $url=$row->old_text;
 225                                 @list( /* $proto */ ,$path)=explode('://',$url,2);
 226                                 if ($path=="") {
 227                                         wfProfileOut( $fname );
 228                                         return false;
 229                                 }
 230                                 $row->old_text=ExternalStore::fetchFromUrl($url);
 231
 232                         }
 233                         if( !in_array( 'object', $flags ) ) {
 234                                 return false;
 235                         }
 236
 237                         if( in_array( 'gzip', $flags ) ) {
 238                                 // This shouldn't happen, but a bug in the compress script
 239                                 // may at times gzip-compress a HistoryBlob object row.
 240                                 $obj = unserialize( gzinflate( $row->old_text ) );
 241                         } else {
 242                                 $obj = unserialize( $row->old_text );
 243                         }
 244
 245                         if( !is_object( $obj ) ) {
 246                                 // Correct for old double-serialization bug.
 247                                 $obj = unserialize( $obj );
 248                         }
 249
 250                         // Save this item for reference; if pulling many
 251                         // items in a row we'll likely use it again.
 252                         $obj->uncompress();
 253                         $wgBlobCache = array( $this->mOldId => $obj );
 254                 }
 255                 return $obj->getItem( $this->mHash );
 256         }
 257
 258         /** @todo document */
 259         function getHash() {
 260                 return $this->mHash;
 261         }
 262 }
 263
 264
 265 /**
 266  * To speed up conversion from 1.4 to 1.5 schema, text rows can refer to the
 267  * leftover cur table as the backend. This avoids expensively copying hundreds
 268  * of megabytes of data during the conversion downtime.
 269  *
 270  * Serialized HistoryBlobCurStub objects will be inserted into the text table
 271  * on conversion if $wgFastSchemaUpgrades is set to true.
 272  *
 273  */
 274 class HistoryBlobCurStub {
 275         var $mCurId;
 276
 277         /** @todo document */
 278         function HistoryBlobCurStub( $curid = 0 ) {
 279                 $this->mCurId = $curid;
 280         }
 281
 282         /**
 283          * Sets the location (cur_id) of the main object to which this object
 284          * points
 285          */
 286         function setLocation( $id ) {
 287                 $this->mCurId = $id;
 288         }
 289
 290         /** @todo document */
 291         function getText() {
 292                 $dbr =& wfGetDB( DB_SLAVE );
 293                 $row = $dbr->selectRow( 'cur', array( 'cur_text' ), array( 'cur_id' => $this->mCurId ) );
 294                 if( !$row ) {
 295                         return false;
 296                 }
 297                 return $row->cur_text;
 298         }
 299 }
 300
 301
 302 ?>