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//
// This example illustrates the use of QPDFObjectHandle::TokenFilter with filterContents. See also
// pdf-filter-tokens.cc for an example that uses QPDFObjectHandle::TokenFilter with
// addContentTokenFilter.
//
#include <cstdlib>
#include <iostream>
#include <qpdf/Pl_StdioFile.hh>
#include <qpdf/QPDF.hh>
#include <qpdf/QPDFObjectHandle.hh>
#include <qpdf/QPDFPageDocumentHelper.hh>
#include <qpdf/QUtil.hh>
static char const* whoami = nullptr;
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() = default;
~StringCounter() override = default;
void handleToken(QPDFTokenizer::Token const&) override;
void handleEOF() override;
int getCount() const;
private:
int count{0};
};
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(std::to_string(this->count));
}
int
StringCounter::getCount() const
{
return this->count;
}
int
main(int argc, char* argv[])
{
whoami = QUtil::getWhoami(argv[0]);
if (argc != 2) {
usage();
}
char const* infilename = argv[1];
try {
QPDF pdf;
pdf.processFile(infilename);
int pageno = 0;
for (auto& page: QPDFPageDocumentHelper(pdf).getAllPages()) {
++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.filterContents(&counter);
} else {
// Write output to stdout for even pages.
Pl_StdioFile out("stdout", stdout);
std::cout << "% Contents of page " << pageno << std::endl;
page.filterContents(&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;
}
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