<?
/*******************************************************************************
** Title.........: download class                                             **
** Summary.......: This class allows to download files with the appropriate   **
**                 headers. Client web browsers recognize the headers, file   **
**                 and mime type and save to disk or offer to open the file   **
**                 using a local application. Files bigger than a given limit **
**                 are automatically compressed defore downloading to the     **
**                 client.                                                    **
** Version.......: 1.0.0                                                      **
** Author........: Klaus P. Pieper <klaus_p.pieper@t-online.de>               **
** Project home..: http://klaus_p.pieper.bei.t-online.de/                     **
** Filename......: class.download.inc                                         **
** Copyright(C)..: 2002 Klaus P. Pieper                                       **
** Last changed..: 28 August 2002                                             **
** License.......: GNU Lesser General Public License (see below)              **
**                                                                            **
**  This library is free software; you can redistribute it and/or             **
**  modify it under the terms of the GNU Lesser General Public                **
**  License as published by the Free Software Foundation; either              **
**  version 2.1 of the License, or (at your option) any later version.        **
**                                                                            **
**  This library is distributed in the hope that it will be useful,           **
**  but WITHOUT ANY WARRANTY; without even the implied warranty of            **
**  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU         **
**  Lesser General Public License for more details.                           **
                                                                              **
**  You should have received a copy of the GNU Lesser General Public          **
**  License along with this library; if not, write to the Free Software       **
**  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA **
*******************************************************************************/

/*******************************************************************************
**  Version history:
**  1.0.0: 28-Aug-2002: first published version
*******************************************************************************/

// define several constants
download::secureDefine("DEF_MIMETYPE", "application/octet-stream");
download::secureDefine("GZ_MIMETYPE", "application/octet-stream");
//download::secureDefine("DEF_READ_BUFFER_SIZE", 32768); // 2^15
download::secureDefine("DEF_READ_BUFFER_SIZE", 33554432); // 2^15
// if file size larger than threshold, then compress file
//download::secureDefine("DEF_COMPRESS_THRESHOLD", 102400); // 100 kB
download::secureDefine("DEF_COMPRESS_THRESHOLD", 33554432); // 32 MB

class download {

  // This defines a constant. If the constant is already defined, it
  // triggers an error.
  // $sDefName: the name of the constant
  // $vDefValue: the value of the constant
  // Returns nothing

  function secureDefine($sDefName, $vDefValue)
  {
      if (defined($sDefName)) {
          trigger_error("$sDefName already defined in __FILE__ line __LINE__",
                  E_USER_WARNING);
      } else {
          define($sDefName, $vDefValue);
      } /* endif */
  } /* end function */

  // This function calls the function trigger_error with a pre-defined format.
  // $sMessage: the error message
  // $iErrorClass: the error class (see php function error_reporting())
  // Returns nothing.

  function error($sMessage, $iErrorClass)
  {
      trigger_error("$sMessage in " . __FILE__ . " line " . __LINE__, $iErrorClass);
  } /* end function */

  // This function compresses an existing file into a temporary file.
  // The function terminates on error using the classes' error function.
  // $sFileName: the name of the existing file
  // $iReadBufferSize: the buffer size which is used by the fread() function
  // Returns the name of the compressed file.

  function compress($sFileName,
                  $iReadBufferSize = DEF_READ_BUFFER_SIZE)
  {
      $hFPi = NULL;   // input file handle
      $hFPo = NULL;   // output file handle
      $sTmpFile = ""; // name of the temporary file
      $sBuf = "";     // read buffer

      // open the input file
      $hFPi = fopen ("$sFileName", "rb");
      if ($hFPi == FALSE) {
          download::error("Can't open file $sFileName", E_USER_ERROR);
      } /* endif */

      // create a temporary file name. Let the function use the system constants.
      $sTmpFile = tempnam(NULL, NULL);
      if ($sTmpFile == FALSE) {
          download::error("Can't create temporary file name", E_USER_ERROR);
      } /* endif */

      // open new file for compression
      $hFPo = gzopen ($sTmpFile, "wb");
      if ($hFPo == FALSE) {
          download::error("Can't open temporary file $sTmpName", E_USER_ERROR);
      } /* endif */

      // read from input and write into output file.
      while (!feof($hFPi)) {
          $sBuf = fread($hFPi, $iReadBufferSize);
          gzwrite ($hFPo, $sBuf);
      } /* endwhile */

      // close both open files.
      gzclose($hFPo);
      fclose($hFPi);

      return $sTmpFile;

  } /* end function */

  // This is the main function of the class. It determines the file size and
  // compresses it if file size is larger than the given limit. Then the
  // headers are sent and finally the download data.
  // Important! No headers must be sent before calling this function!!!
  // $sFileName: the name of the file which will be sent
  // $sDownloadName: the name as it will be shown in the browser
  // $sMimeType: the file (mime) type
  // $iCompressThreshold: the limit for compressing files.
  //       Set to --1 if no compression shall be performed.
  // $iReadBufferSize: the buffer size used by the fread() function
  // Returns nothing.

  function dlFile($sFileName,
                  $sDownloadName = NULL,
                  $sMimeType = NULL,
                  $iCompressThreshold = NULL,
                  $iReadBufferSize = NULL)
  {

      $hFPi = NULL; // input file handle
      $hFPo = NULL; // output file handle
      $sBuf = "";   // read buffer
      $bRemoveFile = FALSE; // boolean flag used for temporary compressed files

      // some defaults
      if ($sMimeType == NULL)          $sMimeType = DEF_MIMETYPE;
      if ($iCompressThreshold == NULL) $iCompressThreshold = DEF_COMPRESS_THRESHOLD;
      if ($iReadBufferSize == NULL)    $iReadBufferSize = DEF_READ_BUFFER_SIZE;

      // buffer output in order to allow modification of http header
      ob_start();

      // if no download name is given, use file name as default
      if ($sDownloadName == NULL) {
         $sDownloadName = $sFileName;
      } /* endif */

      // file size > compression threshold?
      if ($iCompressThreshold > 0 && filesize($sFileName) >= $iCompressThreshold) {

          // compress into temporary file, store resulting file name
          $sFileName = download::compress($sFileName, $iCompressThreshold);
          // mark file for later removal
          $bRemoveFile = TRUE;
          // sent first header line
          header("Content-Type: " . GZ_MIMETYPE);
          // add extension to download file name
          $sDownloadName .= ".gz";

      } else {

          // sent first header line
          header("Content-Type: $sMimeType");
      } /* endif */

      // sent second header line
      header("Content-Disposition: inline; filename=$sDownloadName");

      // open input file (may have been compressed)
      $hFPi = fopen ("$sFileName", "rb");
      if ($hFPi == FALSE) {
          download::error("Can't open file $sFileName", E_USER_ERROR);
          } /* endif */

      // sent third header line with file size
      header("Content-Length: " . filesize($sFileName));

      // now sent data
      while (!feof($hFPi)) {
          $sBuf = fread ($hFPi, $iReadBufferSize);
          echo $sBuf;
      } /* endwhile */

      // close input file
      fclose ($hFPi);

      // flush data to client
      ob_end_flush();

      // now remove any temporary file
      if ($bRemoveFile == TRUE) {
          if (unlink ($sFileName) == FALSE) {
             download::error("Can't unlink file $sFileName", E_USER_ERROR);
          } /* endif */
      } /* endif */

  } /* end function */

}

?>