Add additional interface for filtering page contents

1 files changed, 131 insertions, 0 deletions

diff --git a/examples/pdf-count-strings.cc b/examples/pdf-count-strings.cc
new file mode 100644
index 00000000..81718298
--- /dev/null
+++ b/examples/pdf-count-strings.cc
@@ -0,0 +1,131 @@
+//
+// This example illustrates the use of QPDFObjectHandle::TokenFilter
+// with filterPageContents. See also pdf-filter-tokens.cc for an
+// example that uses QPDFObjectHandle::TokenFilter with
+// addContentTokenFilter.
+//
+
+#include <iostream>
+#include <string.h>
+#include <stdlib.h>
+
+#include <qpdf/QPDF.hh>
+#include <qpdf/QUtil.hh>
+#include <qpdf/QPDFObjectHandle.hh>
+#include <qpdf/Pl_StdioFile.hh>
+
+static char const* whoami = 0;
+
+void usage()
+{
+    std::cerr << "Usage: " << whoami << " infile" << std::endl
+	      << "Applies token filters to infile"
+              << std::endl;
+    exit(2);
+}
+
+class StringCounter: public QPDFObjectHandle::TokenFilter
+{
+  public:
+    StringCounter() :
+        count(0)
+    {
+    }
+    virtual ~StringCounter()
+    {
+    }
+    virtual void handleToken(QPDFTokenizer::Token const&);
+    virtual void handleEOF();
+    int getCount() const;
+
+  private:
+    int count;
+};
+
+void
+StringCounter::handleToken(QPDFTokenizer::Token const& token)
+{
+    // Count string tokens
+    if (token.getType() == QPDFTokenizer::tt_string)
+    {
+        ++this->count;
+    }
+    // Preserve input verbatim by passing each token to any specified
+    // downstream filter.
+    writeToken(token);
+}
+
+void
+StringCounter::handleEOF()
+{
+    // Write a comment at the end of the stream just to show how we
+    // can enhance the output if we want.
+    write("\n% strings found: ");
+    write(QUtil::int_to_string(this->count));
+    // If you override handleEOF, you must always remember to call finish().
+    finish();
+}
+
+int
+StringCounter::getCount() const
+{
+    return this->count;
+}
+
+int main(int argc, char* argv[])
+{
+    whoami = QUtil::getWhoami(argv[0]);
+
+    // For libtool's sake....
+    if (strncmp(whoami, "lt-", 3) == 0)
+    {
+	whoami += 3;
+    }
+
+    if (argc != 2)
+    {
+	usage();
+    }
+    char const* infilename = argv[1];
+
+    try
+    {
+	QPDF pdf;
+	pdf.processFile(infilename);
+        std::vector<QPDFObjectHandle> pages = pdf.getAllPages();
+        int pageno = 0;
+        for (std::vector<QPDFObjectHandle>::iterator iter = pages.begin();
+             iter != pages.end(); ++iter)
+        {
+            QPDFObjectHandle page = *iter;
+            ++pageno;
+            // Pass the contents of a page through our string counter.
+            // If it's an even page, capture the output. This
+            // illustrates that you may capture any output generated
+            // by the filter, or you may ignore it.
+            StringCounter counter;
+            if (pageno % 2)
+            {
+                // Ignore output for odd pages.
+                page.filterPageContents(&counter);
+            }
+            else
+            {
+                // Write output to stdout for even pages.
+                Pl_StdioFile out("stdout", stdout);
+                std::cout << "% Contents of page " << pageno << std::endl;
+                page.filterPageContents(&counter, &out);
+                std::cout << "\n% end " << pageno << std::endl;
+            }
+            std::cout << "Page " << pageno
+                      << ": strings = " << counter.getCount() << std::endl;
+        }
+    }
+    catch (std::exception& e)
+    {
+	std::cerr << whoami << ": " << e.what() << std::endl;
+	exit(2);
+    }
+
+    return 0;
+}