private int CountPDFPages()
{
{
string cached_count_filename = MakeFilename_PageCount();
// Try the cached version
try
{
if (File.Exists(cached_count_filename))
{
int num_pages = Convert.ToInt32(File.ReadAllText(cached_count_filename));
if (0 != num_pages)
{
return(num_pages);
}
}
}
catch (Exception ex)
{
Logging.Warn(ex, "There was a problem loading the cached page count.");
FileTools.Delete(cached_count_filename);
}
}
// If we get here, either the pagecountfile doesnt exist, or there was an exception
{
string cached_count_filename = MakeFilename_PageCount();
Logging.Debug("Using calculated PDF page count");
int num_pages = PDFTools.CountPDFPages(pdf_filename);
if (0 != num_pages)
{
Directory.CreateDirectory(Path.GetDirectoryName(cached_count_filename));
File.WriteAllText(cached_count_filename, "" + num_pages);
}
return(num_pages);
}
}
private int CountPDFPages()
{
string cached_count_filename = MakeFilename_PageCount();
int num;
// Try the cached version
try
{
if (File.Exists(cached_count_filename))
{
num = Convert.ToInt32(File.ReadAllText(cached_count_filename));
if (0 != num)
{
return(num);
}
}
}
catch (Exception ex)
{
Logging.Warn(ex, "There was a problem loading the cached page count.");
FileTools.Delete(cached_count_filename);
}
// If we get here, either the pagecountfile doesn't exist, or there was an exception
Logging.Debug特("Using calculated PDF page count for file {0}", pdf_filename);
num = PDFTools.CountPDFPages(pdf_filename);
Logging.Info("The result is {1} for using calculated PDF page count for file {0}", pdf_filename, num);
do
{
if (0 != num)
{
num_pages_calc_try_count = 0; // reset recalc fail counter
try
{
Directory.CreateDirectory(Path.GetDirectoryName(cached_count_filename));
string outputText = Convert.ToString(num, 10);
File.WriteAllText(cached_count_filename, outputText);
// Open the file and read back what was written: we don't do a file lock for this one, but reckon all threads who
// do this, will produce the same number = file content.
//
// Besides, we don't know if WriteAllText() is atomic; it probably is not.
// Hence we read back to verify written content and if there's anything off about it, we
// blow it out of the water and retry later, possibly.
string readText = File.ReadAllText(cached_count_filename);
if (readText != outputText)
{
throw new IOException("CountPDFPages: cache content as read back from cache file does not match written data. Cache file is untrustworthy.");
}
}
catch (Exception ex)
{
Logging.Error(ex, "There was a problem using calculated PDF page count for file {0} / {1}", pdf_filename, cached_count_filename);
FileTools.Delete(cached_count_filename);
// we know the *calculated* pagecount is A-okay, so we can pass that on.
// It's just the file I/O for caching the value that may have gone awry,
// so we should retry that the next time we (re)calculate the pagecount number
// as it is a heavy operation!
//
//num = 0;
}
}
else
{
// Special case: when the CountPDFPages() API does not deliver a sane, that is non-zero, page count,
// then we've got a PDF file issue on our hands, very probably a damaged PDF.
//
// Damaged PDF files SHOULD NOT burden us forever, hence we introduce the heauristic of Three Strikes:
// when we've (re)calculated the PDF page count three times in a row with errors (num == 0), then we
// don't retry ever again, at least not during this application run.
//
// we DO NOT count I/O errors around the cache file, we only count (re)calc errors:
num_pages_calc_try_count++;
if (num_pages_calc_try_count >= 3)
{
num = -1; // signal final failure
Logging.Warn("Marking this PDF Document as uncompromisingly stubborn in its failure to be inspected for file {0}", pdf_filename);
continue; // and cache this value
}
}
break;
} while (true);
return(num);
}
