inc/classes/main/stacker/file/class_BaseFileStack.php

   1 <?php
   2 /**
   3  * A general file-based stack class
   4  *
   5  * @author              Roland Haeder <webmaster@ship-simu.org>
   6  * @version             0.0.0
   7  * @copyright   Copyright (c) 2007, 2008 Roland Haeder, 2009 - 2013 Core Developer Team
   8  * @license             GNU GPL 3.0 or any newer version
   9  * @link                http://www.ship-simu.org
  10  *
  11  * This program is free software: you can redistribute it and/or modify
  12  * it under the terms of the GNU General Public License as published by
  13  * the Free Software Foundation, either version 3 of the License, or
  14  * (at your option) any later version.
  15  *
  16  * This program is distributed in the hope that it will be useful,
  17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19  * GNU General Public License for more details.
  20  *
  21  * You should have received a copy of the GNU General Public License
  22  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  23  */
  24 class BaseFileStack extends BaseStacker {
  25         /**
  26          * Magic for this stack
  27          */
  28         const STACK_MAGIC = 'STACKv0.1';
  29
  30         /**
  31          * Separator for header data
  32          */
  33         const SEPARATOR_HEADER_DATA = 0x01;
  34
  35         /**
  36          * Separator header->entries
  37          */
  38         const SEPARATOR_HEADER_ENTRIES = 0x02;
  39
  40         /**
  41          * Separator hash->name
  42          */
  43         const SEPARATOR_HASH_NAME = 0x03;
  44
  45         /**
  46          * Length of name
  47          */
  48         const LENGTH_NAME = 10;
  49
  50         /**
  51          * Length of count
  52          */
  53         const LENGTH_COUNT = 20;
  54
  55         /**
  56          * Length of position
  57          */
  58         const LENGTH_POSITION = 20;
  59
  60         /**
  61          * Counter for total entries
  62          */
  63         private $totalEntries = 0;
  64
  65         /**
  66          * Current seek position
  67          */
  68         private $seekPosition = 0;
  69
  70         /**
  71          * Size of header
  72          */
  73         private $headerSize = 0;
  74
  75         /**
  76          * File header
  77          */
  78         private $header = array();
  79
  80         /**
  81          * Seek positions for gaps ("fragmentation")
  82          */
  83         private $gaps = array();
  84
  85         /**
  86          * Seek positions for damaged entries (e.g. mismatching hash sum, ...)
  87          */
  88         private $damagedEntries = array();
  89
  90         /**
  91          * Protected constructor
  92          *
  93          * @param       $className      Name of the class
  94          * @return      void
  95          */
  96         protected function __construct ($className) {
  97                 // Call parent constructor
  98                 parent::__construct($className);
  99
 100                 // Calculate header size
 101                 $this->headerSize = (
 102                         strlen(self::STACK_MAGIC) +
 103                         strlen(self::SEPARATOR_HEADER_DATA) +
 104                         self::LENGTH_COUNT +
 105                         strlen(self::SEPARATOR_HEADER_DATA) +
 106                         self::LENGTH_POSITION +
 107                         strlen(self::SEPARATOR_HEADER_ENTRIES)
 108                 );
 109
 110                 // Init counters and gaps array
 111                 $this->initCountersGapsArray();
 112         }
 113
 114         /**
 115          * Initializes counter for valid entries, arrays for damaged entries and
 116          * an array for gap seek positions. If you call this method on your own,
 117          * please re-analyze the file structure. So you are better to call
 118          * analyzeStackFile() instead of this method.
 119          *
 120          * @return      void
 121          */
 122         private function initCountersGapsArray () {
 123                 // Init counter and seek position
 124                 $this->setCounter(0);
 125                 $this->setSeekPosition(0);
 126
 127                 // Init arrays
 128                 $this->gaps = array();
 129                 $this->damagedEntries = array();
 130         }
 131
 132         /**
 133          * Getter for total entries
 134          *
 135          * @return      $totalEntries   Total entries in this stack
 136          */
 137         private final function getCounter () {
 138                 // Get it
 139                 return $this->totalEntries;
 140         }
 141
 142         /**
 143          * Increment counter
 144          *
 145          * @return      void
 146          */
 147         private final function incrementCounter () {
 148                 // Get it
 149                 $this->totalEntries++;
 150         }
 151
 152         /**
 153          * Getter for seek position
 154          *
 155          * @return      $seekPosition   Current seek position (stored here in object)
 156          */
 157         private final function getSeekPosition () {
 158                 // Get it
 159                 return $this->seekPosition;
 160         }
 161
 162         /**
 163          * Setter for seek position
 164          *
 165          * @param       $seekPosition   Current seek position (stored here in object)
 166          * @return      void
 167          */
 168         private final function setSeekPosition ($seekPosition) {
 169                 // And set it
 170                 $this->seekPosition = $seekPosition;
 171         }
 172
 173         /**
 174          * Updates seekPosition attribute from file to avoid to much access on file.
 175          *
 176          * @return      void
 177          */
 178         private function updateSeekPosition () {
 179                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 180
 181                 // Get key (= seek position)
 182                 $seekPosition = $this->getIteratorInstance()->key();
 183                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Setting seekPosition=%s', __METHOD__, __LINE__, $seekPosition));
 184
 185                 // And set it here
 186                 $this->setSeekPosition($seekPosition);
 187
 188                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!', __METHOD__, __LINE__));
 189         }
 190
 191         /**
 192          * Reads the file header
 193          *
 194          * @return      void
 195          */
 196         private function readFileHeader () {
 197                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 198
 199                 // First rewind to beginning as the header sits at the beginning ...
 200                 $this->getIteratorInstance()->rewind();
 201
 202                 // Then read it (see constructor for calculation)
 203                 $data = $this->getIteratorInstance()->read($this->headerSize);
 204                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Read %d bytes (%d wanted).', __METHOD__, __LINE__, strlen($data), $this->headerSize));
 205
 206                 // Have all requested bytes been read?
 207                 assert(strlen($data) == $this->headerSize);
 208                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Passed assert().', __METHOD__, __LINE__));
 209
 210                 // Last character must be the separator
 211                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] data(-1)=%s', __METHOD__, __LINE__, dechex(ord(substr($data, -1, 1)))));
 212                 assert(substr($data, -1, 1) == chr(self::SEPARATOR_HEADER_ENTRIES));
 213                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Passed assert().', __METHOD__, __LINE__));
 214
 215                 // Okay, then remove it
 216                 $data = substr($data, 0, -1);
 217
 218                 // And update seek position
 219                 $this->updateSeekPosition();
 220
 221                 /*
 222                  * Now split it:
 223                  *
 224                  * 0 => Magic
 225                  * 1 => Total entries
 226                  * 2 => Current seek position
 227                  */
 228                 $this->header = explode(chr(self::SEPARATOR_HEADER_DATA), $data);
 229
 230                 // Check if the array has only 3 elements
 231                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] header(%d)=%s', __METHOD__, __LINE__, count($this->header), print_r($this->header, TRUE)));
 232                 assert(count($this->header) == 3);
 233                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Passed assert().', __METHOD__, __LINE__));
 234
 235                 // Check magic
 236                 assert($this->header[0] == self::STACK_MAGIC);
 237                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Passed assert().', __METHOD__, __LINE__));
 238
 239                 // Check length of count and seek position
 240                 assert(strlen($this->header[1]) == self::LENGTH_COUNT);
 241                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Passed assert().', __METHOD__, __LINE__));
 242                 assert(strlen($this->header[2]) == self::LENGTH_POSITION);
 243                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Passed assert().', __METHOD__, __LINE__));
 244
 245                 // Decode count and seek position
 246                 $this->header[1] = hex2bin($this->header[1]);
 247                 $this->header[2] = hex2bin($this->header[2]);
 248
 249                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!', __METHOD__, __LINE__));
 250         }
 251
 252         /**
 253          * Checks whether the file header is initialized
 254          *
 255          * @return      $isInitialized  Whether the file header is initialized
 256          */
 257         private function isFileHeaderInitialized () {
 258                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 259                 // Default is not initialized
 260                 $isInitialized = FALSE;
 261
 262                 // Is the file initialized?
 263                 if ($this->isFileInitialized()) {
 264                         // Some bytes has been written, so rewind to start of it.
 265                         $rewindStatus = $this->getIteratorInstance()->rewind();
 266                         //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] rewindStatus=%s', __METHOD__, __LINE__, $rewindStatus));
 267
 268                         // Is the rewind() call successfull?
 269                         if ($rewindStatus != 1) {
 270                                 // Something bad happened
 271                                 self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Could not rewind().', __METHOD__, __LINE__));
 272                         } // END - if
 273
 274                         // Read file header
 275                         $this->readFileHeader();
 276
 277                         // The above method does already check the header
 278                         $isInitialized = TRUE;
 279                 } // END - if
 280
 281                 // Return result
 282                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] isInitialized=%d - EXIT!', __METHOD__, __LINE__, intval($isInitialized)));
 283                 return $isInitialized;
 284         }
 285
 286         /**
 287          * Checks whether the file-based stack has been initialized
 288          *
 289          * @return      $isInitialized          Whether the file's size is zero
 290          */
 291         private function isFileInitialized () {
 292                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 293
 294                 // Get it from iterator which holds the pointer instance. If FALSE is returned
 295                 $fileSize = $this->getIteratorInstance()->size();
 296                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] fileSize=%s', __METHOD__, __LINE__, $fileSize));
 297
 298                 /*
 299                  * The returned file size should not be FALSE or NULL as this means
 300                  * that the pointer class does not work correctly.
 301                  */
 302                 assert(is_int($fileSize));
 303
 304                 // Is more than 0 returned?
 305                 $isInitialized = ($fileSize > 0);
 306
 307                 // Return result
 308                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] isInitialized=%d - EXIT!', __METHOD__, __LINE__, intval($isInitialized)));
 309                 return $isInitialized;
 310         }
 311
 312         /**
 313          * Creates the file-stack's header
 314          *
 315          * @return      void
 316          */
 317         private function createFileHeader () {
 318                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 319                 // The file's header should not be initialized here
 320                 assert(!$this->isFileHeaderInitialized());
 321
 322                 // Simple flush file header which will create it.
 323                 $this->flushFileHeader();
 324
 325                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!!', __METHOD__, __LINE__));
 326         }
 327
 328         /**
 329          * Flushes the file header
 330          *
 331          * @return      void
 332          */
 333         private function flushFileHeader () {
 334                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 335
 336                 // Put all informations together
 337                 $header = sprintf('%s%s%s%s%s%s',
 338                         // Magic
 339                         self::STACK_MAGIC,
 340
 341                         // Separator magic<->count
 342                         chr(self::SEPARATOR_HEADER_DATA),
 343
 344                         // Total entries (will be zero) and pad it to 20 chars
 345                         str_pad($this->dec2hex($this->getCounter()), self::LENGTH_COUNT, '0', STR_PAD_LEFT),
 346
 347                         // Separator count<->seek position
 348                         chr(self::SEPARATOR_HEADER_DATA),
 349
 350                         // Position (will be zero)
 351                         str_pad($this->dec2hex($this->getSeekPosition(), 2), self::LENGTH_POSITION, '0', STR_PAD_LEFT),
 352
 353                         // Separator position<->entries
 354                         chr(self::SEPARATOR_HEADER_ENTRIES)
 355                 );
 356
 357                 // Write it to disk (header is always at seek position 0)
 358                 $this->writeData(0, $header);
 359
 360                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!', __METHOD__, __LINE__));
 361         }
 362
 363         /**
 364          * Writes data at given position
 365          *
 366          * @param       $seekPosition   Seek position
 367          * @param       $data                   Data to be written
 368          * @return      void
 369          */
 370         private function writeData ($seekPosition, $data) {
 371                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] seekPosition=%s,data()=%s - CALLED!', __METHOD__, __LINE__, $seekPosition, strlen($data)));
 372
 373                 // Write data at given position
 374                 $this->getIteratorInstance()->writeAtPosition($seekPosition, $data);
 375
 376                 // Update seek position
 377                 $this->updateSeekPosition();
 378
 379                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!', __METHOD__, __LINE__));
 380         }
 381
 382         /**
 383          * Pre-allocates file (if enabled) with some space for later faster write access.
 384          *
 385          * @return      void
 386          */
 387         private function preAllocateFile () {
 388                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 389
 390                 // Is it enabled?
 391                 if ($this->getConfigInstance()->getConfigEntry('file_stack_pre_allocate_enabled') != 'Y') {
 392                         // Not enabled
 393                         self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Not pre-allocating stack file.', __METHOD__, __LINE__));
 394
 395                         // Don't continue here.
 396                         return;
 397                 } // END - if
 398
 399                 // Message to user
 400                 self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Pre-allocating stack file ...', __METHOD__, __LINE__));
 401
 402                 /*
 403                  * Calculate minimum length for one entry:
 404                  * minimum length = hash length + separator + name + minimum entry size = ?? + 1 + 10 + 1 = ??
 405                  */
 406                 $minLengthEntry = self::getHashLength() + strlen(self::SEPARATOR_HASH_NAME) + self::LENGTH_NAME + 1;
 407                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] minLengthEntry=%s', __METHOD__, __LINE__, $minLengthEntry));
 408
 409                 // Calulcate seek position
 410                 $seekPosition = $minLengthEntry * $this->getConfigInstance()->getConfigEntry('file_stack_pre_allocate_count');
 411                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] seekPosition=%s', __METHOD__, __LINE__, $seekPosition));
 412
 413                 // Now simply write a NUL there. This will pre-allocate the file.
 414                 $this->writeData($seekPosition, chr(0));
 415
 416                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!', __METHOD__, __LINE__));
 417         }
 418
 419         /**
 420          * Analyzes entries in stack file. This will count all found (and valid)
 421          * entries, mark invalid as damaged and count gaps ("fragmentation"). If
 422          * only gaps are found, the file is considered as "virgin" (no entries).
 423          *
 424          * @return      void
 425          */
 426         private function analyzeStackFile () {
 427                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] CALLED!', __METHOD__, __LINE__));
 428
 429                 // Make sure the file is initialized
 430                 assert($this->isFileInitialized());
 431
 432                 // Init counters and gaps array
 433                 $this->initCountersGapsArray();
 434
 435                 // Output message (as this may take some time)
 436                 self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] Analyzing file structure ... (this may take some time)', __METHOD__, __LINE__));
 437
 438                 //* NOISY-DEBUG: */ self::createDebugInstance(__CLASS__)->debugOutput(sprintf('[%s:%d:] EXIT!', __METHOD__, __LINE__));
 439         }
 440
 441         /**
 442          * Initializes this file-based stack.
 443          *
 444          * @param       $fileName       File name of this stack
 445          * @return      void
 446          */
 447         protected function initFileStack ($fileName) {
 448                 // Get a file i/o pointer instance for stack file
 449                 $pointerInstance = ObjectFactory::createObjectByConfiguredName('file_raw_input_output_class', array($fileName));
 450
 451                 // Get iterator instance
 452                 $iteratorInstance = ObjectFactory::createObjectByConfiguredName('file_io_iterator_class', array($pointerInstance));
 453
 454                 // Is the instance implementing the right interface?
 455                 assert($iteratorInstance instanceof SeekableWritableFileIterator);
 456
 457                 // Set iterator here
 458                 $this->setIteratorInstance($iteratorInstance);
 459
 460                 // Is the file's header initialized?
 461                 if (!$this->isFileHeaderInitialized()) {
 462                         // No, then create it (which may pre-allocate the stack)
 463                         $this->createFileHeader();
 464
 465                         // And pre-allocate a bit
 466                         $this->preAllocateFile();
 467                 } // END - if
 468
 469                 // Load the file header
 470                 $this->readFileHeader();
 471
 472                 // Count all entries in file
 473                 $this->analyzeStackFile();
 474
 475                 /*
 476                  * Get stack index instance. This can be used for faster
 477                  * "defragmentation" and startup.
 478                  */
 479                 $indexInstance = FileStackIndexFactory::createFileStackIndex($fileName);
 480
 481                 // And set it here
 482                 $this->setIndexInstance($indexInstance);
 483         }
 484
 485         /**
 486          * Adds a value to given stack
 487          *
 488          * @param       $stackerName    Name of the stack
 489          * @param       $value                  Value to add to this stacker
 490          * @return      void
 491          * @throws      FullStackerException    If the stack is full
 492          */
 493         protected function addValue ($stackerName, $value) {
 494                 // Do some tests
 495                 if ($this->isStackFull($stackerName)) {
 496                         // Stacker is full
 497                         throw new FullStackerException(array($this, $stackerName, $value), self::EXCEPTION_STACKER_IS_FULL);
 498                 } // END - if
 499
 500                 // Now add the value to the stack
 501                 $this->partialStub('stackerName=' . $stackerName . ',value[]=' . gettype($value));
 502         }
 503
 504         /**
 505          * Get last value from named stacker
 506          *
 507          * @param       $stackerName    Name of the stack
 508          * @return      $value                  Value of last added value
 509          * @throws      EmptyStackerException   If the stack is empty
 510          */
 511         protected function getLastValue ($stackerName) {
 512                 // Is the stack not yet initialized or full?
 513                 if ($this->isStackEmpty($stackerName)) {
 514                         // Throw an exception
 515                         throw new EmptyStackerException(array($this, $stackerName), self::EXCEPTION_STACKER_IS_EMPTY);
 516                 } // END - if
 517
 518                 // Now get the last value
 519                 $this->partialStub('stackerName=' . $stackerName);
 520                 $value = NULL;
 521
 522                 // Return it
 523                 return $value;
 524         }
 525
 526         /**
 527          * Get first value from named stacker
 528          *
 529          * @param       $stackerName    Name of the stack
 530          * @return      $value                  Value of last added value
 531          * @throws      EmptyStackerException   If the stack is empty
 532          */
 533         protected function getFirstValue ($stackerName) {
 534                 // Is the stack not yet initialized or full?
 535                 if ($this->isStackEmpty($stackerName)) {
 536                         // Throw an exception
 537                         throw new EmptyStackerException(array($this, $stackerName), self::EXCEPTION_STACKER_IS_EMPTY);
 538                 } // END - if
 539
 540                 // Now get the first value
 541                 $this->partialStub('stackerName=' . $stackerName);
 542                 $value = NULL;
 543
 544                 // Return it
 545                 return $value;
 546         }
 547
 548         /**
 549          * "Pops" last entry from stack
 550          *
 551          * @param       $stackerName    Name of the stack
 552          * @return      $value                  Value "poped" from array
 553          * @throws      EmptyStackerException   If the stack is empty
 554          */
 555         protected function popLast ($stackerName) {
 556                 // Is the stack not yet initialized or full?
 557                 if ($this->isStackEmpty($stackerName)) {
 558                         // Throw an exception
 559                         throw new EmptyStackerException(array($this, $stackerName), self::EXCEPTION_STACKER_IS_EMPTY);
 560                 } // END - if
 561
 562                 // Now, remove the last entry, we don't care about the return value here, see elseif() block above
 563                 $this->partialStub('stackerName=' . $stackerName);
 564                 return NULL;
 565         }
 566
 567         /**
 568          * "Pops" first entry from stack
 569          *
 570          * @param       $stackerName    Name of the stack
 571          * @return      $value                  Value "shifted" from array
 572          * @throws      EmptyStackerException   If the named stacker is empty
 573          */
 574         protected function popFirst ($stackerName) {
 575                 // Is the stack not yet initialized or full?
 576                 if ($this->isStackEmpty($stackerName)) {
 577                         // Throw an exception
 578                         throw new EmptyStackerException(array($this, $stackerName), self::EXCEPTION_STACKER_IS_EMPTY);
 579                 } // END - if
 580
 581                 // Now, remove the last entry, we don't care about the return value here, see elseif() block above
 582                 $this->partialStub('stackerName=' . $stackerName);
 583                 return NULL;
 584         }
 585
 586         /**
 587          * Checks whether the given stack is full
 588          *
 589          * @param       $stackerName    Name of the stack
 590          * @return      $isFull                 Whether the stack is full
 591          */
 592         protected function isStackFull ($stackerName) {
 593                 // File-based stacks will only run full if the disk space is low.
 594                 // @TODO Please implement this, returning FALSE
 595                 $isFull = FALSE;
 596
 597                 // Return result
 598                 return $isFull;
 599         }
 600
 601         /**
 602          * Checks whether the given stack is empty
 603          *
 604          * @param       $stackerName            Name of the stack
 605          * @return      $isEmpty                        Whether the stack is empty
 606          * @throws      NoStackerException      If given stack is missing
 607          */
 608         public function isStackEmpty ($stackerName) {
 609                 // So, is the stack empty?
 610                 $isEmpty = (($this->getStackCount($stackerName)) == 0);
 611
 612                 // Return result
 613                 return $isEmpty;
 614         }
 615
 616         /**
 617          * Initializes given stacker
 618          *
 619          * @param       $stackerName    Name of the stack
 620          * @param       $forceReInit    Force re-initialization
 621          * @return      void
 622          * @throws      UnsupportedOperationException   This method is not (and maybe never will be) supported
 623          */
 624         public function initStack ($stackerName, $forceReInit = FALSE) {
 625                 throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
 626         }
 627
 628         /**
 629          * Initializes all stacks
 630          *
 631          * @return      void
 632          * @throws      UnsupportedOperationException   This method is not (and maybe never will be) supported
 633          */
 634         public function initStacks (array $stacks, $forceReInit = FALSE) {
 635                 throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
 636         }
 637
 638         /**
 639          * Checks whether the given stack is initialized (set in array $stackers)
 640          *
 641          * @param       $stackerName    Name of the stack
 642          * @return      $isInitialized  Whether the stack is initialized
 643          * @throws      UnsupportedOperationException   This method is not (and maybe never will be) supported
 644          */
 645         public function isStackInitialized ($stackerName) {
 646                 throw new UnsupportedOperationException(array($this, __FUNCTION__, $this->getIteratorInstance()->getPointerInstance()), self::EXCEPTION_UNSPPORTED_OPERATION);
 647         }
 648
 649         /**
 650          * Getter for size of given stack (array count)
 651          *
 652          * @param       $stackerName    Name of the stack
 653          * @return      $count                  Size of stack (array count)
 654          */
 655         public function getStackCount ($stackerName) {
 656                 // Now, simply return the found count value, this must be up-to-date then!
 657                 return $this->getCounter();
 658         }
 659 }
 660
 661 // [EOF]
 662 ?>