name/number trees: newEmpty, increment/decrement end()

include/qpdf/QPDFNameTreeObjectHelper.hh

@@ -54,6 +54,12 @@ class QPDFNameTreeObjectHelper: public QPDFObjectHelper
     // structure.
     QPDF_DLL
     QPDFNameTreeObjectHelper(QPDFObjectHandle);
+
+    // Create an empty name tree
+    QPDF_DLL
+    static QPDFNameTreeObjectHelper newEmpty(QPDF&, bool auto_repair = true);
+
+    // ABI: = default
     QPDF_DLL
     virtual ~QPDFNameTreeObjectHelper();
 
@@ -112,7 +118,9 @@ class QPDFNameTreeObjectHelper: public QPDFObjectHelper
     };
 
     // The iterator looks like map iterator, so i.first is a string
-    // and i.second is a QPDFObjectHandle.
+    // and i.second is a QPDFObjectHandle. Incrementing end() brings
+    // you to the first item. Decrementing end() brings you to the
+    // last item.
     QPDF_DLL
     iterator begin() const;
     QPDF_DLL

include/qpdf/QPDFNumberTreeObjectHelper.hh

@@ -51,11 +51,17 @@ class QPDFNumberTreeObjectHelper: public QPDFObjectHelper
     // structure.
     QPDF_DLL
     QPDFNumberTreeObjectHelper(QPDFObjectHandle);
+
+    // ABI: = default
     QPDF_DLL
     virtual ~QPDFNumberTreeObjectHelper()
     {
     }
 
+    // Create an empty number tree
+    QPDF_DLL
+    static QPDFNumberTreeObjectHelper newEmpty(QPDF&, bool auto_repair = true);
+
     typedef long long int numtree_number;
 
     // Return overall minimum and maximum indices
@@ -131,7 +137,9 @@ class QPDFNumberTreeObjectHelper: public QPDFObjectHelper
     };
 
     // The iterator looks like map iterator, so i.first is a string
-    // and i.second is a QPDFObjectHandle.
+    // and i.second is a QPDFObjectHandle. Incrementing end() brings
+    // you to the first item. Decrementing end() brings you to the
+    // last item.
     QPDF_DLL
     iterator begin() const;
     QPDF_DLL

libqpdf/NNTree.cc

@@ -103,9 +103,9 @@ NNTreeIterator::increment(bool backward)
 {
     if (this->item_number < 0)
     {
-        throw std::logic_error(
-            "attempt made to increment or decrement an invalid"
-            " name/number tree iterator");
+        QTC::TC("qpdf", "NNTree increment end()");
+        deepen(impl.oh, ! backward, true);
+        return;
     }
     bool found_valid_key = false;
     while (valid() && (! found_valid_key))

libqpdf/QPDFNameTreeObjectHelper.cc

@@ -56,6 +56,13 @@ QPDFNameTreeObjectHelper::~QPDFNameTreeObjectHelper()
 {
 }
 
+QPDFNameTreeObjectHelper
+QPDFNameTreeObjectHelper::newEmpty(QPDF& qpdf, bool auto_repair)
+{
+    return QPDFNameTreeObjectHelper(
+        QPDFObjectHandle::parse("<< /Names [] >>"), qpdf, auto_repair);
+}
+
 QPDFNameTreeObjectHelper::iterator::iterator(
     std::shared_ptr<NNTreeIterator> const& i) :
     impl(i)

libqpdf/QPDFNumberTreeObjectHelper.cc

@@ -52,6 +52,13 @@ QPDFNumberTreeObjectHelper::QPDFNumberTreeObjectHelper(QPDFObjectHandle oh) :
 {
 }
 
+QPDFNumberTreeObjectHelper
+QPDFNumberTreeObjectHelper::newEmpty(QPDF& qpdf, bool auto_repair)
+{
+    return QPDFNumberTreeObjectHelper(
+        QPDFObjectHandle::parse("<< /Nums [] >>"), qpdf, auto_repair);
+}
+
 QPDFNumberTreeObjectHelper::iterator::iterator(
     std::shared_ptr<NNTreeIterator> const& i) :
     impl(i)

qpdf/qpdf.testcov

@@ -551,3 +551,4 @@ NNTree -1 in binary search 0
 NNTree bad node during find 0
 NNTree node is not a dictionary 0
 NNTree limits didn't change 0
+NNTree increment end() 0

qpdf/test_driver.cc

@@ -1776,6 +1776,32 @@ void runtest(int n, char const* filename1, char const* arg2)
         assert("six" == oh.getStringValue());
         assert(2 == offset);
 
+        auto new1 = QPDFNumberTreeObjectHelper::newEmpty(pdf);
+        auto iter1 = new1.begin();
+        assert(iter1 == new1.end());
+        ++iter1;
+        assert(iter1 == new1.end());
+        --iter1;
+        assert(iter1 == new1.end());
+        new1.insert(1, QPDFObjectHandle::newString("1"));
+        ++iter1;
+        assert((*iter1).first == 1);
+        --iter1;
+        assert(iter1 == new1.end());
+        --iter1;
+        assert((*iter1).first == 1);
+        new1.insert(2, QPDFObjectHandle::newString("2"));
+        ++iter1;
+        assert((*iter1).first == 2);
+        ++iter1;
+        assert(iter1 == new1.end());
+        ++iter1;
+        assert((*iter1).first == 1);
+        --iter1;
+        assert(iter1 == new1.end());
+        --iter1;
+        assert((*iter1).first == 2);
+
         // Exercise deprecated API until qpdf 11
         std::cout << "/Bad1: deprecated API" << std::endl;
         auto bad1 = QPDFNumberTreeObjectHelper(
@@ -1909,6 +1935,32 @@ void runtest(int n, char const* filename1, char const* arg2)
         assert((*last).first == "29 twenty-nine");
         assert((*last).second.getUTF8Value() == "twenty-nine!");
 
+        auto new1 = QPDFNameTreeObjectHelper::newEmpty(pdf);
+        auto iter1 = new1.begin();
+        assert(iter1 == new1.end());
+        ++iter1;
+        assert(iter1 == new1.end());
+        --iter1;
+        assert(iter1 == new1.end());
+        new1.insert("1", QPDFObjectHandle::newString("1"));
+        ++iter1;
+        assert((*iter1).first == "1");
+        --iter1;
+        assert(iter1 == new1.end());
+        --iter1;
+        assert((*iter1).first == "1");
+        new1.insert("2", QPDFObjectHandle::newString("2"));
+        ++iter1;
+        assert((*iter1).first == "2");
+        ++iter1;
+        assert(iter1 == new1.end());
+        ++iter1;
+        assert((*iter1).first == "1");
+        --iter1;
+        assert(iter1 == new1.end());
+        --iter1;
+        assert((*iter1).first == "2");
+
         std::vector<std::string> empties = {"/Empty1", "/Empty2"};
         for (auto const& k: empties)
         {