Add QPDFPageLabelDocumentHelper

1 files changed, 125 insertions, 0 deletions

diff --git a/libqpdf/QPDFPageLabelDocumentHelper.cc b/libqpdf/QPDFPageLabelDocumentHelper.cc
new file mode 100644
index 00000000..63be5809
--- /dev/null
+++ b/libqpdf/QPDFPageLabelDocumentHelper.cc
@@ -0,0 +1,125 @@
+#include <qpdf/QPDFPageLabelDocumentHelper.hh>
+#include <qpdf/QTC.hh>
+
+QPDFPageLabelDocumentHelper::Members::~Members()
+{
+}
+
+QPDFPageLabelDocumentHelper::Members::Members()
+{
+}
+
+QPDFPageLabelDocumentHelper::QPDFPageLabelDocumentHelper(QPDF& qpdf) :
+    QPDFDocumentHelper(qpdf),
+    m(new Members())
+{
+    QPDFObjectHandle root = qpdf.getRoot();
+    if (root.hasKey("/PageLabels"))
+    {
+        this->m->labels = new QPDFNumberTreeObjectHelper(
+            root.getKey("/PageLabels"));
+    }
+}
+
+bool
+QPDFPageLabelDocumentHelper::hasPageLabels()
+{
+    return 0 != this->m->labels.getPointer();
+}
+
+QPDFObjectHandle
+QPDFPageLabelDocumentHelper::getLabelForPage(long long page_idx)
+{
+    QPDFObjectHandle result(QPDFObjectHandle::newNull());
+    if (! hasPageLabels())
+    {
+        return result;
+    }
+    QPDFNumberTreeObjectHelper::numtree_number offset = 0;
+    QPDFObjectHandle label;
+    if (! this->m->labels->findObjectAtOrBelow(page_idx, label, offset))
+    {
+        return result;
+    }
+    if (! label.isDictionary())
+    {
+        return result;
+    }
+    QPDFObjectHandle S = label.getKey("/S");   // type (D, R, r, A, a)
+    QPDFObjectHandle P = label.getKey("/P");   // prefix
+    QPDFObjectHandle St = label.getKey("/St"); // starting number
+    long long start = 1;
+    if (St.isInteger())
+    {
+        start = St.getIntValue();
+    }
+    start += offset;
+    result = QPDFObjectHandle::newDictionary();
+    result.replaceOrRemoveKey("/S", S);
+    result.replaceOrRemoveKey("/P", P);
+    result.replaceOrRemoveKey("/St", QPDFObjectHandle::newInteger(start));
+    return result;
+}
+
+void
+QPDFPageLabelDocumentHelper::getLabelsForPageRange(
+    long long start_idx, long long end_idx, long long new_start_idx,
+    std::vector<QPDFObjectHandle>& new_labels)
+{
+    // Start off with a suitable label for the first page. For every
+    // remaining page, if that page has an explicit entry, copy it.
+    // Otherwise, let the subsequent page just sequence from the prior
+    // entry. If there is no entry for the first page, fabricate one
+    // that would match how the page would look in a new file in which
+    // it also didn't have an explicit label.
+    QPDFObjectHandle label = getLabelForPage(start_idx);
+    if (label.isNull())
+    {
+        label = QPDFObjectHandle::newDictionary();
+        label.replaceKey(
+            "/St", QPDFObjectHandle::newInteger(1 + new_start_idx));
+    }
+    // See if the new label is redundant based on the previous entry
+    // in the vector. If so, don't add it.
+    size_t size = new_labels.size();
+    bool skip_first = false;
+    if (size >= 2)
+    {
+        QPDFObjectHandle last = new_labels[size - 1];
+        QPDFObjectHandle last_idx = new_labels[size - 2];
+        if (last_idx.isInteger() && last.isDictionary() &&
+            (label.getKey("/S").unparse() == last.getKey("/S").unparse()) &&
+            (label.getKey("/P").unparse() == last.getKey("/P").unparse()) &&
+            label.getKey("/St").isInteger() &&
+            last.getKey("/St").isInteger())
+        {
+            long long int st_delta =
+                label.getKey("/St").getIntValue() -
+                last.getKey("/St").getIntValue();
+            long long int idx_delta =
+                new_start_idx - last_idx.getIntValue();
+            if (st_delta == idx_delta)
+            {
+                QTC::TC("qpdf", "QPDFPageLabelDocumentHelper skip first");
+                skip_first = true;
+            }
+        }
+    }
+    if (! skip_first)
+    {
+        new_labels.push_back(QPDFObjectHandle::newInteger(new_start_idx));
+        new_labels.push_back(label);
+    }
+
+    long long int idx_offset = new_start_idx - start_idx;
+    for (long long i = start_idx + 1; i <= end_idx; ++i)
+    {
+        if (this->m->labels->hasIndex(i) &&
+            (label = getLabelForPage(i)).isDictionary())
+        {
+            new_labels.push_back(QPDFObjectHandle::newInteger(i + idx_offset));
+            new_labels.push_back(label);
+        }
+    }
+}
+