includes/ZipDirectoryReader.php

   1 <?php
   2
   3 /**
   4  * A class for reading ZIP file directories, for the purposes of upload
   5  * verification.
   6  *
   7  * Only a functional interface is provided: ZipFileReader::read(). No access is
   8  * given to object instances.
   9  *
  10  */
  11 class ZipDirectoryReader {
  12         /**
  13          * Read a ZIP file and call a function for each file discovered in it.
  14          *
  15          * Because this class is aimed at verification, an error is raised on
  16          * suspicious or ambiguous input, instead of emulating some standard
  17          * behaviour.
  18          *
  19          * @param $fileName The archive file name
  20          * @param $callback The callback function. It will be called for each file
  21          *   with a single associative array each time, with members:
  22          *
  23          *      - name: The file name. Directories conventionally have a trailing
  24          *        slash.
  25          *
  26          *      - mtime: The file modification time, in MediaWiki 14-char format
  27          *
  28          *      - size: The uncompressed file size
  29          *
  30          * @param $options An associative array of read options, with the option
  31          *    name in the key. This may currently contain:
  32          *
  33          *      - zip64: If this is set to true, then we will emulate a
  34          *        library with ZIP64 support, like OpenJDK 7. If it is set to
  35          *        false, then we will emulate a library with no knowledge of
  36          *        ZIP64.
  37          *
  38          *        NOTE: The ZIP64 code is untested and probably doesn't work. It
  39          *        turned out to be easier to just reject ZIP64 archive uploads,
  40          *        since they are likely to be very rare. Confirming safety of a
  41          *        ZIP64 file is fairly complex. What do you do with a file that is
  42          *        ambiguous and broken when read with a non-ZIP64 reader, but valid
  43          *        when read with a ZIP64 reader? This situation is normal for a
  44          *        valid ZIP64 file, and working out what non-ZIP64 readers will make
  45          *        of such a file is not trivial.
  46          *
  47          * @return A Status object. The following fatal errors are defined:
  48          *
  49          *      - zip-file-open-error: The file could not be opened.
  50          *
  51          *      - zip-wrong-format: The file does not appear to be a ZIP file.
  52          *
  53          *      - zip-bad: There was something wrong or ambiguous about the file
  54          *        data.
  55          *
  56          *      - zip-unsupported: The ZIP file uses features which
  57          *        ZipDirectoryReader does not support.
  58          *
  59          * The default messages for those fatal errors are written in a way that
  60          * makes sense for upload verification.
  61          *
  62          * If a fatal error is returned, more information about the error will be
  63          * available in the debug log.
  64          *
  65          * Note that the callback function may be called any number of times before
  66          * a fatal error is returned. If this occurs, the data sent to the callback
  67          * function should be discarded.
  68          */
  69         public static function read( $fileName, $callback, $options = array() ) {
  70                 $zdr = new self( $fileName, $callback, $options );
  71                 return $zdr->execute();
  72         }
  73
  74         /** The file name */
  75         var $fileName;
  76
  77         /** The opened file resource */
  78         var $file;
  79
  80         /** The cached length of the file, or null if it has not been loaded yet. */
  81         var $fileLength;
  82
  83         /** A segmented cache of the file contents */
  84         var $buffer;
  85
  86         /** The file data callback */
  87         var $callback;
  88
  89         /** The ZIP64 mode */
  90         var $zip64 = false;
  91
  92         /** Stored headers */
  93         var $eocdr, $eocdr64, $eocdr64Locator;
  94
  95         /** The "extra field" ID for ZIP64 central directory entries */
  96         const ZIP64_EXTRA_HEADER = 0x0001;
  97
  98         /** The segment size for the file contents cache */
  99         const SEGSIZE = 16384;
 100
 101         /** The index of the "general field" bit for UTF-8 file names */
 102         const GENERAL_UTF8 = 11;
 103
 104         /** The index of the "general field" bit for central directory encryption */
 105         const GENERAL_CD_ENCRYPTED = 13;
 106
 107
 108         /**
 109          * Private constructor
 110          */
 111         protected function __construct( $fileName, $callback, $options ) {
 112                 $this->fileName = $fileName;
 113                 $this->callback = $callback;
 114
 115                 if ( isset( $options['zip64'] ) ) {
 116                         $this->zip64 = $options['zip64'];
 117                 }
 118         }
 119
 120         /**
 121          * Read the directory according to settings in $this.
 122          */
 123         function execute() {
 124                 $this->file = fopen( $this->fileName, 'r' );
 125                 $this->data = array();
 126                 if ( !$this->file ) {
 127                         return Status::newFatal( 'zip-file-open-error' );
 128                 }
 129
 130                 $status = Status::newGood();
 131                 try {
 132                         $this->readEndOfCentralDirectoryRecord();
 133                         if ( $this->zip64 ) {
 134                                 list( $offset, $size ) = $this->findZip64CentralDirectory();
 135                                 $this->readCentralDirectory( $offset, $size );
 136                         } else {
 137                                 if ( $this->eocdr['CD size'] == 0xffffffff
 138                                         || $this->eocdr['CD offset'] == 0xffffffff
 139                                         || $this->eocdr['CD entries total'] == 0xffff )
 140                                 {
 141                                         $this->error( 'zip-unsupported', 'Central directory header indicates ZIP64, ' .
 142                                                 'but we are in legacy mode. Rejecting this upload is necessary to avoid '.
 143                                                 'opening vulnerabilities on clients using OpenJDK 7 or later.' );
 144                                 }
 145
 146                                 list( $offset, $size ) = $this->findOldCentralDirectory();
 147                                 $this->readCentralDirectory( $offset, $size );
 148                         }
 149                 } catch ( ZipDirectoryReaderError $e ) {
 150                         $status->fatal( $e->getErrorCode() );
 151                 }
 152
 153                 fclose( $this->file );
 154                 return $status;
 155         }
 156
 157         /**
 158          * Throw an error, and log a debug message
 159          */
 160         function error( $code, $debugMessage ) {
 161                 wfDebug( __CLASS__.": Fatal error: $debugMessage\n" );
 162                 throw new ZipDirectoryReaderError( $code );
 163         }
 164
 165         /**
 166          * Read the header which is at the end of the central directory,
 167          * unimaginatively called the "end of central directory record" by the ZIP
 168          * spec.
 169          */
 170         function readEndOfCentralDirectoryRecord() {
 171                 $info = array(
 172                         'signature' => 4,
 173                         'disk' => 2,
 174                         'CD start disk' => 2,
 175                         'CD entries this disk' => 2,
 176                         'CD entries total' => 2,
 177                         'CD size' => 4,
 178                         'CD offset' => 4,
 179                         'file comment length' => 2,
 180                 );
 181                 $structSize = $this->getStructSize( $info );
 182                 $startPos = $this->getFileLength() - 65536 - $structSize;
 183                 if ( $startPos < 0 ) {
 184                         $startPos = 0;
 185                 }
 186
 187                 $block = $this->getBlock( $startPos );
 188                 $sigPos = strrpos( $block, "PK\x05\x06" );
 189                 if ( $sigPos === false ) {
 190                         $this->error( 'zip-wrong-format',
 191                                 "zip file lacks EOCDR signature. It probably isn't a zip file." );
 192                 }
 193
 194                 $this->eocdr = $this->unpack( substr( $block, $sigPos ), $info );
 195                 $this->eocdr['EOCDR size'] = $structSize + $this->eocdr['file comment length'];
 196
 197                 if ( $structSize + $this->eocdr['file comment length'] != strlen( $block ) - $sigPos ) {
 198                         $this->error( 'zip-bad', 'trailing bytes after the end of the file comment' );
 199                 }
 200                 if (   $this->eocdr['disk'] !== 0
 201                         || $this->eocdr['CD start disk'] !== 0 )
 202                 {
 203                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR)' );
 204                 }
 205                 $this->eocdr += $this->unpack(
 206                         $block,
 207                         array( 'file comment' => array( 'string', $this->eocdr['file comment length'] ) ),
 208                         $sigPos + $structSize );
 209                 $this->eocdr['position'] = $startPos + $sigPos;
 210         }
 211
 212         /**
 213          * Read the header called the "ZIP64 end of central directory locator". An
 214          * error will be raised if it does not exist.
 215          */
 216         function readZip64EndOfCentralDirectoryLocator() {
 217                 $info = array(
 218                         'signature' => array( 'string', 4 ),
 219                         'eocdr64 start disk' => 4,
 220                         'eocdr64 offset' => 8,
 221                         'number of disks' => 4,
 222                 );
 223                 $structSize = $this->getStructSize( $info );
 224
 225                 $block = $this->getBlock( $this->getFileLength() - $this->eocdr['EOCDR size']
 226                         - $structSize, $structSize );
 227                 $this->eocdr64Locator = $data = $this->unpack( $block, $info );
 228
 229                 if ( $data['signature'] !== "PK\x06\x07" ) {
 230                         // Note: Java will allow this and continue to read the
 231                         // EOCDR64, so we have to reject the upload, we can't
 232                         // just use the EOCDR header instead.
 233                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory locator' );
 234                 }
 235         }
 236
 237         /**
 238          * Read the header called the "ZIP64 end of central directory record". It
 239          * may replace the regular "end of central directory record" in ZIP64 files.
 240          */
 241         function readZip64EndOfCentralDirectoryRecord() {
 242                 if (   $this->eocdr64Locator['eocdr64 start disk'] != 0
 243                         || $this->eocdr64Locator['number of disks'] != 0 )
 244                 {
 245                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64 locator)' );
 246                 }
 247
 248                 $info = array(
 249                         'signature' => array( 'string', 4 ),
 250                         'EOCDR64 size' => 8,
 251                         'version made by' => 2,
 252                         'version needed' => 2,
 253                         'disk' => 4,
 254                         'CD start disk' => 4,
 255                         'CD entries this disk' => 8,
 256                         'CD entries total' => 8,
 257                         'CD size' => 8,
 258                         'CD offset' => 8
 259                 );
 260                 $structSize = $this->getStructSize( $info );
 261                 $block = $this->getBlock( $this->eocdr64Locator['eocdr64 offset'], $structSize );
 262                 $this->eocdr64 = $data = $this->unpack( $block, $info );
 263                 if ( $data['signature'] !== "PK\x06\x06" ) {
 264                         $this->error( 'zip-bad', 'wrong signature on Zip64 end of central directory record' );
 265                 }
 266                 if (   $data['disk'] !== 0
 267                         || $data['CD start disk'] !== 0 )
 268                 {
 269                         $this->error( 'zip-unsupported', 'more than one disk (in EOCDR64)' );
 270                 }
 271         }
 272
 273         /**
 274          * Find the location of the central directory, as would be seen by a
 275          * non-ZIP64 reader.
 276          *
 277          * @return List containing offset, size and end position.
 278          */
 279         function findOldCentralDirectory() {
 280                 $size = $this->eocdr['CD size'];
 281                 $offset = $this->eocdr['CD offset'];
 282                 $endPos = $this->eocdr['position'];
 283
 284                 // Some readers use the EOCDR position instead of the offset field
 285                 // to find the directory, so to be safe, we check if they both agree.
 286                 if ( $offset + $size != $endPos ) {
 287                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 288                                 'of central directory record' );
 289                 }
 290                 return array( $offset, $size );
 291         }
 292
 293         /**
 294          * Find the location of the central directory, as would be seen by a
 295          * ZIP64-compliant reader.
 296          *
 297          * @return List containing offset, size and end position.
 298          */
 299         function findZip64CentralDirectory() {
 300                 // The spec is ambiguous about the exact rules of precedence between the
 301                 // ZIP64 headers and the original headers. Here we follow zip_util.c
 302                 // from OpenJDK 7.
 303                 $size = $this->eocdr['CD size'];
 304                 $offset = $this->eocdr['CD offset'];
 305                 $numEntries = $this->eocdr['CD entries total'];
 306                 $endPos = $this->eocdr['position'];
 307                 if (   $size == 0xffffffff
 308                         || $offset == 0xffffffff
 309                         || $numEntries == 0xffff )
 310                 {
 311                         $this->readZip64EndOfCentralDirectoryLocator();
 312
 313                         if ( isset( $this->eocdr64Locator['eocdr64 offset'] ) ) {
 314                                 $this->readZip64EndOfCentralDirectoryRecord();
 315                                 if ( isset( $this->eocdr64['CD offset'] ) ) {
 316                                         $size = $this->eocdr64['CD size'];
 317                                         $offset = $this->eocdr64['CD offset'];
 318                                         $endPos = $this->eocdr64Locator['eocdr64 offset'];
 319                                 }
 320                         }
 321                 }
 322                 // Some readers use the EOCDR position instead of the offset field
 323                 // to find the directory, so to be safe, we check if they both agree.
 324                 if ( $offset + $size != $endPos ) {
 325                         $this->error( 'zip-bad', 'the central directory does not immediately precede the end ' .
 326                                 'of central directory record' );
 327                 }
 328                 return array( $offset, $size );
 329         }
 330
 331         /**
 332          * Read the central directory at the given location
 333          */
 334         function readCentralDirectory( $offset, $size ) {
 335                 $block = $this->getBlock( $offset, $size );
 336
 337                 $fixedInfo = array(
 338                         'signature' => array( 'string', 4 ),
 339                         'version made by' => 2,
 340                         'version needed' => 2,
 341                         'general bits' => 2,
 342                         'compression method' => 2,
 343                         'mod time' => 2,
 344                         'mod date' => 2,
 345                         'crc-32' => 4,
 346                         'compressed size' => 4,
 347                         'uncompressed size' => 4,
 348                         'name length' => 2,
 349                         'extra field length' => 2,
 350                         'comment length' => 2,
 351                         'disk number start' => 2,
 352                         'internal attrs' => 2,
 353                         'external attrs' => 4,
 354                         'local header offset' => 4,
 355                 );
 356                 $fixedSize = $this->getStructSize( $fixedInfo );
 357
 358                 $pos = 0;
 359                 while ( $pos < $size ) {
 360                         $data = $this->unpack( $block, $fixedInfo, $pos );
 361                         $pos += $fixedSize;
 362
 363                         if ( $data['signature'] !== "PK\x01\x02" ) {
 364                                 $this->error( 'zip-bad', 'Invalid signature found in directory entry' );
 365                         }
 366
 367                         $variableInfo = array(
 368                                 'name' => array( 'string', $data['name length'] ),
 369                                 'extra field' => array( 'string', $data['extra field length'] ),
 370                                 'comment' => array( 'string', $data['comment length'] ),
 371                         );
 372                         $data += $this->unpack( $block, $variableInfo, $pos );
 373                         $pos += $this->getStructSize( $variableInfo );
 374
 375                         if (   $this->zip64 && (
 376                                    $data['compressed size'] == 0xffffffff
 377                                 || $data['uncompressed size'] == 0xffffffff
 378                                 || $data['local header offset'] == 0xffffffff ) )
 379                         {
 380                                 $zip64Data = $this->unpackZip64Extra( $data['extra field'] );
 381                                 if ( $zip64Data ) {
 382                                         $data = $zip64Data + $data;
 383                                 }
 384                         }
 385
 386                         if ( $this->testBit( $data['general bits'], self::GENERAL_CD_ENCRYPTED ) ) {
 387                                 $this->error( 'zip-unsupported', 'central directory encryption is not supported' );
 388                         }
 389
 390                         // Convert the timestamp into MediaWiki format
 391                         // For the format, please see the MS-DOS 2.0 Programmer's Reference,
 392                         // pages 3-5 and 3-6.
 393                         $time = $data['mod time'];
 394                         $date = $data['mod date'];
 395
 396                         $year = 1980 + ( $date >> 9 );
 397                         $month = ( $date >> 5 ) & 15;
 398                         $day = $date & 31;
 399                         $hour = ( $time >> 11 ) & 31;
 400                         $minute = ( $time >> 5 ) & 63;
 401                         $second = ( $time & 31 ) * 2;
 402                         $timestamp = sprintf( "%04d%02d%02d%02d%02d%02d",
 403                                 $year, $month, $day, $hour, $minute, $second );
 404
 405                         // Convert the character set in the file name
 406                         if ( !function_exists( 'iconv' )
 407                                 || $this->testBit( $data['general bits'], self::GENERAL_UTF8 ) )
 408                         {
 409                                 $name = $data['name'];
 410                         } else {
 411                                 $name = iconv( 'CP437', 'UTF-8', $data['name'] );
 412                         }
 413
 414                         // Compile a data array for the user, with a sensible format
 415                         $userData = array(
 416                                 'name' => $name,
 417                                 'mtime' => $timestamp,
 418                                 'size' => $data['uncompressed size'],
 419                         );
 420                         call_user_func( $this->callback, $userData );
 421                 }
 422         }
 423
 424         /**
 425          * Interpret ZIP64 "extra field" data and return an associative array.
 426          */
 427         function unpackZip64Extra( $extraField ) {
 428                 $extraHeaderInfo = array(
 429                         'id' => 2,
 430                         'size' => 2,
 431                 );
 432                 $extraHeaderSize = $this->getStructSize( $extraHeaderInfo );
 433
 434                 $zip64ExtraInfo = array(
 435                         'uncompressed size' => 8,
 436                         'compressed size' => 8,
 437                         'local header offset' => 8,
 438                         'disk number start' => 4,
 439                 );
 440
 441                 $extraPos = 0;
 442                 while ( $extraPos < strlen( $extraField ) ) {
 443                         $extra = $this->unpack( $extraField, $extraHeaderInfo, $extraPos );
 444                         $extraPos += $extraHeaderSize;
 445                         $extra += $this->unpack( $extraField,
 446                                 array( 'data' => array( 'string', $extra['size'] ) ),
 447                                 $extraPos );
 448                         $extraPos += $extra['size'];
 449
 450                         if ( $extra['id'] == self::ZIP64_EXTRA_HEADER ) {
 451                                 return $this->unpack( $extra['data'], $zip64ExtraInfo );
 452                         }
 453                 }
 454
 455                 return false;
 456         }
 457
 458         /**
 459          * Get the length of the file.
 460          */
 461         function getFileLength() {
 462                 if ( $this->fileLength === null ) {
 463                         $stat = fstat( $this->file );
 464                         $this->fileLength = $stat['size'];
 465                 }
 466                 return $this->fileLength;
 467         }
 468
 469         /**
 470          * Get the file contents from a given offset. If there are not enough bytes
 471          * in the file to satisfy the request, an exception will be thrown.
 472          *
 473          * @param $start The byte offset of the start of the block.
 474          * @param $length The number of bytes to return. If omitted, the remainder
 475          *    of the file will be returned.
 476          *
 477          * @return string
 478          */
 479         function getBlock( $start, $length = null ) {
 480                 $fileLength = $this->getFileLength();
 481                 if ( $start >= $fileLength ) {
 482                         $this->error( 'zip-bad', "getBlock() requested position $start, " .
 483                                 "file length is $fileLength" );
 484                 }
 485                 if ( $length === null ) {
 486                         $length = $fileLength - $start;
 487                 }
 488                 $end = $start + $length;
 489                 if ( $end > $fileLength ) {
 490                         $this->error( 'zip-bad', "getBlock() requested end position $end, " .
 491                                 "file length is $fileLength" );
 492                 }
 493                 $startSeg = floor( $start / self::SEGSIZE );
 494                 $endSeg = ceil( $end / self::SEGSIZE );
 495
 496                 $block = '';
 497                 for ( $segIndex = $startSeg; $segIndex <= $endSeg; $segIndex++ ) {
 498                         $block .= $this->getSegment( $segIndex );
 499                 }
 500
 501                 $block = substr( $block,
 502                         $start - $startSeg * self::SEGSIZE,
 503                         $length );
 504
 505                 if ( strlen( $block ) < $length ) {
 506                         $this->error( 'zip-bad', 'getBlock() returned an unexpectedly small amount of data' );
 507                 }
 508
 509                 return $block;
 510         }
 511
 512         /**
 513          * Get a section of the file starting at position $segIndex * self::SEGSIZE,
 514          * of length self::SEGSIZE. The result is cached. This is a helper function
 515          * for getBlock().
 516          *
 517          * If there are not enough bytes in the file to satsify the request, the
 518          * return value will be truncated. If a request is made for a segment beyond
 519          * the end of the file, an empty string will be returned.
 520          */
 521         function getSegment( $segIndex ) {
 522                 if ( !isset( $this->buffer[$segIndex] ) ) {
 523                         $bytePos = $segIndex * self::SEGSIZE;
 524                         if ( $bytePos >= $this->getFileLength() ) {
 525                                 $this->buffer[$segIndex] = '';
 526                                 return '';
 527                         }
 528                         if ( fseek( $this->file, $bytePos ) ) {
 529                                 $this->error( 'zip-bad', "seek to $bytePos failed" );
 530                         }
 531                         $seg = fread( $this->file, self::SEGSIZE );
 532                         if ( $seg === false ) {
 533                                 $this->error( 'zip-bad', "read from $bytePos failed" );
 534                         }
 535                         $this->buffer[$segIndex] = $seg;
 536                 }
 537                 return $this->buffer[$segIndex];
 538         }
 539
 540         /**
 541          * Get the size of a structure in bytes. See unpack() for the format of $struct.
 542          */
 543         function getStructSize( $struct ) {
 544                 $size = 0;
 545                 foreach ( $struct as $key => $type ) {
 546                         if ( is_array( $type ) ) {
 547                                 list( $typeName, $fieldSize ) = $type;
 548                                 $size += $fieldSize;
 549                         } else {
 550                                 $size += $type;
 551                         }
 552                 }
 553                 return $size;
 554         }
 555
 556         /**
 557          * Unpack a binary structure. This is like the built-in unpack() function
 558          * except nicer.
 559          *
 560          * @param $string The binary data input
 561          *
 562          * @param $struct An associative array giving structure members and their
 563          *    types. In the key is the field name. The value may be either an
 564          *    integer, in which case the field is a little-endian unsigned integer
 565          *    encoded in the given number of bytes, or an array, in which case the
 566          *    first element of the array is the type name, and the subsequent
 567          *    elements are type-dependent parameters. Only one such type is defined:
 568          *       - "string": The second array element gives the length of string.
 569          *          Not null terminated.
 570          *
 571          * @param $offset The offset into the string at which to start unpacking.
 572          *
 573          * @return Unpacked associative array. Note that large integers in the input
 574          *    may be represented as floating point numbers in the return value, so
 575          *    the use of weak comparison is advised.
 576          */
 577         function unpack( $string, $struct, $offset = 0 ) {
 578                 $size = $this->getStructSize( $struct );
 579                 if ( $offset + $size > strlen( $string ) ) {
 580                         $this->error( 'zip-bad', 'unpack() would run past the end of the supplied string' );
 581                 }
 582
 583                 $data = array();
 584                 $pos = $offset;
 585                 foreach ( $struct as $key => $type ) {
 586                         if ( is_array( $type ) ) {
 587                                 list( $typeName, $fieldSize ) = $type;
 588                                 switch ( $typeName ) {
 589                                 case 'string':
 590                                         $data[$key] = substr( $string, $pos, $fieldSize );
 591                                         $pos += $fieldSize;
 592                                         break;
 593                                 default:
 594                                         throw new MWException( __METHOD__.": invalid type \"$typeName\"" );
 595                                 }
 596                         } else {
 597                                 // Unsigned little-endian integer
 598                                 $length = intval( $type );
 599                                 $bytes = substr( $string, $pos, $length );
 600
 601                                 // Calculate the value. Use an algorithm which automatically
 602                                 // upgrades the value to floating point if necessary.
 603                                 $value = 0;
 604                                 for ( $i = $length - 1; $i >= 0; $i-- ) {
 605                                         $value *= 256;
 606                                         $value += ord( $string[$pos + $i] );
 607                                 }
 608
 609                                 // Throw an exception if there was loss of precision
 610                                 if ( $value > pow( 2, 52 ) ) {
 611                                         $this->error( 'zip-unsupported', 'number too large to be stored in a double. ' .
 612                                                 'This could happen if we tried to unpack a 64-bit structure ' .
 613                                                 'at an invalid location.' );
 614                                 }
 615                                 $data[$key] = $value;
 616                                 $pos += $length;
 617                         }
 618                 }
 619
 620                 return $data;
 621         }
 622
 623         /**
 624          * Returns a bit from a given position in an integer value, converted to
 625          * boolean.
 626          *
 627          * @param $value integer
 628          * @param $bitIndex The index of the bit, where 0 is the LSB.
 629          */
 630         function testBit( $value, $bitIndex ) {
 631                 return (bool)( ( $value >> $bitIndex ) & 1 );
 632         }
 633
 634         /**
 635          * Debugging helper function which dumps a string in hexdump -C format.
 636          */
 637         function hexDump( $s ) {
 638                 $n = strlen( $s );
 639                 for ( $i = 0; $i < $n; $i += 16 ) {
 640                         printf( "%08X ", $i );
 641                         for ( $j = 0; $j < 16; $j++ ) {
 642                                 print " ";
 643                                 if ( $j == 8 ) {
 644                                         print " ";
 645                                 }
 646                                 if ( $i + $j >= $n ) {
 647                                         print "  ";
 648                                 } else {
 649                                         printf( "%02X", ord( $s[$i + $j] ) );
 650                                 }
 651                         }
 652
 653                         print "  |";
 654                         for ( $j = 0; $j < 16; $j++ ) {
 655                                 if ( $i + $j >= $n ) {
 656                                         print " ";
 657                                 } elseif ( ctype_print( $s[$i + $j] ) ) {
 658                                         print $s[$i + $j];
 659                                 } else {
 660                                         print '.';
 661                                 }
 662                         }
 663                         print "|\n";
 664                 }
 665         }
 666 }
 667
 668 /**
 669  * Internal exception class. Will be caught by private code.
 670  */
 671 class ZipDirectoryReaderError extends Exception {
 672         var $code;
 673
 674         function __construct( $code ) {
 675                 $this->code = $code;
 676                 parent::__construct( "ZipDirectoryReader error: $code" );
 677         }
 678
 679         function getErrorCode() {
 680                 return $this->code;
 681         }
 682 }