Fix infinite loop on small files with progress reporting (fixes #230)

Turns out you can keep adding zero to a number over and over again and
it just doesn't get any bigger. Who would have known?

ChangeLog

@@ -1,3 +1,8 @@
+2018-08-05  Jay Berkenbilt  <ejb@ql.org>
+
+	* Bug fix: infinite loop on progress reporting for very small
+	files. Fixes #230.
+
 2018-08-04  Jay Berkenbilt  <ejb@ql.org>
 
 	* Performance fix: optimize page merging operation to avoid

libqpdf/QPDFWriter.cc

@@ -3357,9 +3357,10 @@ QPDFWriter::indicateProgress(bool decrement, bool finished)
                                 this->m->events_expected)));
         this->m->progress_reporter->reportProgress(percentage);
     }
+    int increment = std::max(1, (this->m->events_expected / 100));
     while (this->m->events_seen >= this->m->next_progress_report)
     {
-        this->m->next_progress_report += (this->m->events_expected / 100);
+        this->m->next_progress_report += increment;
     }
 }
 

qpdf/qtest/qpdf.test

@@ -925,6 +925,17 @@ $td->runtest("don't overwrite self",
              {$td->REGEXP => "input file and output file are the same.*",
               $td->EXIT_STATUS => 2});
 
+show_ntests();
+# ----------
+$td->notify("--- Progress reporting ---");
+$n_tests += 1;
+
+$td->runtest("progress report on small file",
+             {$td->COMMAND => "qpdf --progress minimal.pdf a.pdf",
+                  $td->FILTER => "perl filter-progress.pl"},
+             {$td->FILE => "small-progress.out", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+
 show_ntests();
 # ----------
 $td->notify("--- Type checks ---");

qpdf/qtest/qpdf/small-progress.out

@@ -0,0 +1,3 @@
+qpdf: a.pdf: write progress: 0%
+....other write progress....
+qpdf: a.pdf: write progress: 100%