mirror of https://github.com/qpdf/qpdf.git
104 lines
2.7 KiB
C++
104 lines
2.7 KiB
C++
//
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// This example illustrates the use of QPDFObjectHandle::TokenFilter with filterContents. See also
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// pdf-filter-tokens.cc for an example that uses QPDFObjectHandle::TokenFilter with
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// addContentTokenFilter.
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//
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#include <cstdlib>
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#include <iostream>
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#include <qpdf/Pl_StdioFile.hh>
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#include <qpdf/QPDF.hh>
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#include <qpdf/QPDFObjectHandle.hh>
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#include <qpdf/QPDFPageDocumentHelper.hh>
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#include <qpdf/QUtil.hh>
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static char const* whoami = nullptr;
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void
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usage()
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{
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std::cerr << "Usage: " << whoami << " infile" << std::endl
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<< "Applies token filters to infile" << std::endl;
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exit(2);
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}
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class StringCounter: public QPDFObjectHandle::TokenFilter
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{
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public:
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StringCounter() = default;
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~StringCounter() override = default;
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void handleToken(QPDFTokenizer::Token const&) override;
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void handleEOF() override;
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int getCount() const;
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private:
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int count{0};
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};
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void
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StringCounter::handleToken(QPDFTokenizer::Token const& token)
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{
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// Count string tokens
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if (token.getType() == QPDFTokenizer::tt_string) {
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++this->count;
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}
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// Preserve input verbatim by passing each token to any specified downstream filter.
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writeToken(token);
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}
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void
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StringCounter::handleEOF()
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{
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// Write a comment at the end of the stream just to show how we can enhance the output if we
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// want.
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write("\n% strings found: ");
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write(std::to_string(this->count));
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}
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int
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StringCounter::getCount() const
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{
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return this->count;
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}
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int
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main(int argc, char* argv[])
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{
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whoami = QUtil::getWhoami(argv[0]);
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if (argc != 2) {
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usage();
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}
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char const* infilename = argv[1];
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try {
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QPDF pdf;
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pdf.processFile(infilename);
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int pageno = 0;
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for (auto& page: QPDFPageDocumentHelper(pdf).getAllPages()) {
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++pageno;
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// Pass the contents of a page through our string counter. If it's an even page, capture
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// the output. This illustrates that you may capture any output generated by the filter,
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// or you may ignore it.
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StringCounter counter;
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if (pageno % 2) {
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// Ignore output for odd pages.
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page.filterContents(&counter);
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} else {
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// Write output to stdout for even pages.
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Pl_StdioFile out("stdout", stdout);
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std::cout << "% Contents of page " << pageno << std::endl;
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page.filterContents(&counter, &out);
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std::cout << "\n% end " << pageno << std::endl;
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}
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std::cout << "Page " << pageno << ": strings = " << counter.getCount() << std::endl;
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}
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} catch (std::exception& e) {
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std::cerr << whoami << ": " << e.what() << std::endl;
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exit(2);
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}
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return 0;
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}
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