pdf-name-number-tree.cc
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#include <qpdf/QPDF.hh>
#include <qpdf/QPDFNameTreeObjectHelper.hh>
#include <qpdf/QPDFNumberTreeObjectHelper.hh>
#include <qpdf/QPDFWriter.hh>
#include <qpdf/QUtil.hh>
#include <iostream>
static char const* whoami = nullptr;
void
usage()
{
std::cerr << "Usage: " << whoami << " outfile.pdf" << '\n'
<< "Create some name/number trees and write to a file\n";
exit(2);
}
int
main(int argc, char* argv[])
{
whoami = QUtil::getWhoami(argv[0]);
if (argc != 2) {
usage();
}
char const* outfilename = argv[1];
QPDF qpdf;
qpdf.emptyPDF();
// This example doesn't do anything particularly useful other than just illustrate how to use
// the APIs for name and number trees. It also demonstrates use of the iterators for
// dictionaries and arrays introduced at the same time with qpdf 10.2.
// To use this example, compile it and run it. Study the output and compare it to what you
// expect. When done, look at the generated output file in a text editor to inspect the
// structure of the trees as left in the file.
// We're just going to create some name and number trees, hang them off the document catalog
// (root), and write an empty PDF to a file. The PDF will have no pages and won't be viewable,
// but you can look at it in a text editor to see the resulting structure of the PDF.
// Create a dictionary off the root where we will hang our name and number trees.
auto root = qpdf.getRoot();
auto example = QPDFObjectHandle::newDictionary();
root.replaceKey("/Example", example);
// Create a name tree, attach it to the file, and add some items.
auto name_tree = QPDFNameTreeObjectHelper::newEmpty(qpdf);
auto name_tree_oh = name_tree.getObjectHandle();
example.replaceKey("/NameTree", name_tree_oh);
name_tree.insert("K", QPDFObjectHandle::newUnicodeString("king"));
name_tree.insert("Q", QPDFObjectHandle::newUnicodeString("queen"));
name_tree.insert("R", QPDFObjectHandle::newUnicodeString("rook"));
name_tree.insert("B", QPDFObjectHandle::newUnicodeString("bishop"));
name_tree.insert("N", QPDFObjectHandle::newUnicodeString("knight"));
auto iter = name_tree.insert("P", QPDFObjectHandle::newUnicodeString("pawn"));
// Look at the iterator
std::cout << "just inserted " << iter->first << " -> " << iter->second.unparse() << '\n';
--iter;
std::cout << "predecessor: " << iter->first << " -> " << iter->second.unparse() << '\n';
++iter;
++iter;
std::cout << "successor: " << iter->first << " -> " << iter->second.unparse() << '\n';
// Use range-for iteration
std::cout << "Name tree items:\n";
for (auto i: name_tree) {
std::cout << " " << i.first << " -> " << i.second.unparse() << '\n';
}
// This is a small tree, so everything will be at the root. We can look at it using dictionary
// and array iterators.
std::cout << "Keys in name tree object:\n";
QPDFObjectHandle names;
for (auto const& i: name_tree_oh.ditems()) {
std::cout << i.first << '\n';
if (i.first == "/Names") {
names = i.second;
}
}
// Values in names array:
std::cout << "Values in names:\n";
for (auto& i: names.aitems()) {
std::cout << " " << i.unparse() << '\n';
}
// pre 10.2 API
std::cout << "Has Q?: " << name_tree.hasName("Q") << '\n';
std::cout << "Has W?: " << name_tree.hasName("W") << '\n';
QPDFObjectHandle obj;
std::cout << "Found W?: " << name_tree.findObject("W", obj) << '\n';
std::cout << "Found Q?: " << name_tree.findObject("Q", obj) << '\n';
std::cout << "Q: " << obj.unparse() << '\n';
// 10.2 API
iter = name_tree.find("Q");
std::cout << "Q: " << iter->first << " -> " << iter->second.unparse() << '\n';
iter = name_tree.find("W");
std::cout << "W found: " << (iter != name_tree.end()) << '\n';
// Allow find to return predecessor
iter = name_tree.find("W", true);
std::cout << "W's predecessor: " << iter->first << " -> " << iter->second.unparse() << '\n';
// We can also remove items
std::cout << "Remove P: " << name_tree.remove("P", &obj) << '\n';
std::cout << "Value removed: " << obj.unparse() << '\n';
std::cout << "Has P?: " << name_tree.hasName("P") << '\n';
// Or we can remove using an iterator
iter = name_tree.find("K");
std::cout << "Find K: " << iter->second.unparse() << '\n';
iter.remove();
std::cout << "Iter after removing K: " << iter->first << " -> " << iter->second.unparse()
<< '\n';
std::cout << "Has K?: " << name_tree.hasName("K") << '\n';
// Illustrate some more advanced usage using number trees. These calls work for name trees too.
// The safe way to populate a tree is to call insert repeatedly as above, but if you know you
// are definitely inserting items in order, it is more efficient to insert them using
// insertAfter, which avoids doing a binary search through the tree for each insertion. Note
// that if you don't insert items in order using this method, you will create an invalid tree.
auto number_tree = QPDFNumberTreeObjectHelper::newEmpty(qpdf);
auto number_tree_oh = number_tree.getObjectHandle();
example.replaceKey("/NumberTree", number_tree_oh);
auto iter2 = number_tree.begin();
for (int i = 7; i <= 350; i += 7) {
iter2.insertAfter(i, QPDFObjectHandle::newString("-" + std::to_string(i) + "-"));
}
std::cout << "Numbers:\n";
int n = 1;
for (auto& i: number_tree) {
std::cout << i.first << " -> " << i.second.getUTF8Value();
if (n % 5) {
std::cout << ", ";
} else {
std::cout << '\n';
}
++n;
}
// When you remove an item with an iterator, the iterator advances. This makes it possible to
// filter while iterating. Remove all items that are multiples of 5.
iter2 = number_tree.begin();
while (iter2 != number_tree.end()) {
if (iter2->first % 5 == 0) {
iter2.remove(); // also advances
} else {
++iter2;
}
}
std::cout << "Numbers after filtering:\n";
n = 1;
for (auto& i: number_tree) {
std::cout << i.first << " -> " << i.second.getUTF8Value();
if (n % 5) {
std::cout << ", ";
} else {
std::cout << '\n';
}
++n;
}
// Write to an output file
QPDFWriter w(qpdf, outfilename);
w.setQDFMode(true);
w.setStaticID(true); // for testing only
w.write();
return 0;
}