Test version of TeX filter designed for moodle.org

diff --git a/filter/tex/mimetex.cgi b/filter/tex/mimetex.cgi
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diff --git a/filter/tex/tex_filter.php b/filter/tex/tex_filter.php
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+<?PHP
+/////////////////////////////////////////////////////////////////////////////
+//                                                                         //
+// NOTICE OF COPYRIGHT                                                     //
+//                                                                         //
+// Moodle - Filter for converting TeX expressions to cached gif images     //
+//                                                                         //
+// Copyright (C) 2004 Zbigniew Fiedorowicz fiedorow@math.ohio-state.edu    //
+// Originally based on code provided by Bruno Vernier bruno@vsbeducation.ca//
+// This program is free software; you can redistribute it and/or modify    //
+// it under the terms of the GNU General Public License as published by    //
+// the Free Software Foundation; either version 2 of the License, or       //
+// (at your option) any later version.                                     //
+//                                                                         //
+// This program 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 General Public License for more details:                            //
+//                                                                         //
+//          http://www.gnu.org/copyleft/gpl.html                           //
+//                                                                         //
+/////////////////////////////////////////////////////////////////////////////
+//-------------------------------------------------------------------------
+// NOTE: This Moodle text filter converts TeX expressions delimited
+// by either $$...$$ or by <tex...>...</tex> tags to gif images using
+// mimetex.cgi obtained from http://www.forkosh.com/mimetex.html authored by
+// John Forkosh john@forkosh.com. The mimetex.cgi ELF binary compiled for Linux i386
+// is included with this distribution. 
+// Note that there may be patent restrictions on the production of gif images
+// in Canada and some parts of Western Europe and Japan until July 2004.
+//-------------------------------------------------------------------------
+// You will then need to edit your moodle/config.php to invoke tex_filter.php
+//-------------------------------------------------------------------------
+
+
+/// Edit these lines to correspond to your installation
+// File path to the directory where mathml_filter.php resides
+    $CFG->filterDirectory = "/var/www/html/moodle1_2d/filter/tex";
+// File paths to the echo binary executable
+    $CFG->echo = "/bin/echo";
+// Frequency with which cache cleanup code is called: 119 means once in 119 times
+// that the filter is invoked
+    $CFG->cacheCleanFreq = 119;
+// Time in seconds after which image gifs which haven't been viewed are considered stale
+// and are scheduled for deletion
+    $CFG->cacheCleanTime = 14*24*3600;
+// Command used to list the oldest cached gif files to be scheduled for deletion, in
+// conjunction with the value of cacheCleanTime
+    $CFG->cleanFiles = "cd ".  $CFG->dataroot . "/1/tex_files;/bin/ls -tr | /usr/bin/head -20";
+
+
+/// These lines are important - the variable must match the name 
+/// of the actual function below
+    $textfilter_function='tex_filter';
+
+    if (function_exists($textfilter_function)) {
+        return;
+    }
+
+
+function string_file_picture($path, $courseid=0, $height="", $width="", $link="") {
+  // Given the path to a picture file in a course, or a URL,
+  // this function includes the picture in the page.
+  global $CFG;
+  $output = "";
+  if ($height) {
+    $height = "height=\"$height\"";
+  }
+  if ($width) {
+    $width = "width=\"$width\"";
+  }
+  if ($link) {
+    $output .= "<a href=\"$link\">";
+  }
+  if (substr(strtolower($path), 0, 7) == "http://") {
+    $output .= "<img border=\"0\" $height $width src=\"$path\" />";
+
+  } else if ($courseid) {
+    $output .= "<img border=\"0\" $height $width src=\"";
+    if ($CFG->slasharguments) {        // Use this method if possible for better caching
+      $output .= "$CFG->wwwroot/file.php/$courseid/$path";
+    } else {
+      $output .= "$CFG->wwwroot/file.php?file=/$courseid/$path";
+    }
+    $output .= "\" />";
+  } else {
+    $output .= "Error: must pass URL or course";
+  }
+  if ($link) {
+    $output .= "</a>";
+  }
+  return $output;
+}
+
+function tex_filter ($courseid, $text) {
+
+    global $CFG;
+    $filterDirectory = $CFG->filterDirectory;
+
+    $scriptname = $_SERVER['SCRIPT_NAME'];
+    if (!strstr($scriptname,'/forum/')) {
+      return $text;
+    }
+    /// Do a quick check using stripos to avoid unnecessary wor
+    if (!preg_match('/<tex/i',$text) && !strstr($text,'$$')) {
+        return $text;
+    }
+    
+    if (strstr($scriptname,'post.php')) {
+      $parent = forum_get_post_full($_GET['reply']);
+      $discussion = get_record("forum_discussions","id",$parent->discussion);
+    } else if (strstr($scriptname,'discuss.php')) {
+      $discussion = get_record("forum_discussions","id",$_GET['d'] );
+    } else {
+      return $text;
+    }
+    if ($discussion->forum != 130) {
+      return $text;
+    }
+    
+    $old_umask = umask();
+
+    if (!file_exists($CFG->dataroot . "/1/")) {
+        mkdir($CFG->dataroot . "/1/",0775);
+    }
+
+    if (!file_exists($CFG->dataroot . "/1/tex_files/")) {
+      mkdir($CFG->dataroot . "/1/tex_files/",0775);
+    }
+    umask($old_umask);
+    echo "\n<!--$CFG->cleanFiles-->\n";
+    if (isadmin()) { error_reporting (E_ALL); }; //for debugging
+    $timenow = time();
+    if (!($timenow % $CFG->cacheCleanFreq)) {
+      $cleanFiles = explode("\n",`$CFG->cleanFiles`);
+      foreach ($cleanFiles as $cleanFile) {
+        $pathname = $CFG->dataroot . "/1/tex_files/" . $cleanFile;
+        if ($timenow - filemtime($pathname)>$CFG->cacheCleanTime) {
+          unlink($pathname);
+        } else {
+          break;
+        }
+      }
+    }
+
+    
+    $text .= ' ';
+    preg_match_all('/\$(\$\$+?)([^\$])/s',$text,$matches);
+    for ($i=0;$i<count($matches[0]);$i++) {
+        $replacement = str_replace('$','&#x00024;',$matches[1][$i]).$matches[2][$i];
+        $text = str_replace($matches[0][$i],$replacement,$text);
+    }
+
+    if (isadmin()) { error_reporting (E_ALL); }; //for debugging
+     
+    // <tex> TeX expression </tex>
+    // or $$ TeX expression $$
+
+    preg_match_all('/<tex>(.+?)<\/tex>|\$\$(.+?)\$\$/is', $text, $matches);  
+    for ($i=0; $i<count($matches[0]); $i++) {
+        $texexp = $matches[1][$i] . $matches[2][$i];
+        $filename = "tex_files/". md5($texexp) . ".gif";
+        $pathname = $CFG->dataroot . "/1/" . $filename;
+        
+        if (file_exists($pathname)) {
+           touch($pathname);
+           $text = str_replace( $matches[0][$i], string_file_picture($filename, 1), $text);
+        } else {
+           $texexp = str_replace('&lt;','<',$texexp);
+           $texexp = str_replace('&gt;','>',$texexp);
+           $texexp = preg_replace('!\r\n?!',' ',$texexp);
+
+           system("QUERY_STRING=;export QUERY_STRING;$filterDirectory/mimetex.cgi -d ". escapeshellarg($texexp) . "  >$pathname");
+          $text = str_replace( $matches[0][$i], string_file_picture($filename, 1), $text);
+        }
+         
+    }
+    return $text; 
+};
+
+
+?>
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