From 0ef2def8ad1f280adc34825b1588d9811d9ac031 Mon Sep 17 00:00:00 2001
From: m-holger <m-holger@kubitscheck.org>
Date: Fri, 16 Dec 2022 18:08:56 +0000
Subject: Delay adding offsets to object descriptions until necessary

---
 libqpdf/QPDFParser.cc      | 19 ++++++-------------
 libqpdf/qpdf/QPDFParser.hh | 10 +++++-----
 libqpdf/qpdf/QPDFValue.hh  |  7 +++++++
 3 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/libqpdf/QPDFParser.cc b/libqpdf/QPDFParser.cc
index 70c328e1..0ce97a8e 100644
--- a/libqpdf/QPDFParser.cc
+++ b/libqpdf/QPDFParser.cc
@@ -288,8 +288,7 @@ QPDFParser::parse(bool& empty, bool content_stream)
             if (!indirect_ref && !is_null) {
                 // No need to set description for direct nulls - they will
                 // become implicit.
-                auto os = input->getLastOffset();
-                setDescription(object, os, os);
+                setDescription(object, input->getLastOffset());
             }
             set_offset = true;
             olist.push_back(is_null ? null_oh : object);
@@ -312,7 +311,7 @@ QPDFParser::parse(bool& empty, bool content_stream)
             state_stack.pop_back();
             if (old_state == st_array) {
                 object = QPDFObjectHandle::newArray(olist);
-                setDescription(object, offset, offset - 1);
+                setDescription(object, offset - 1);
                 // The `offset` points to the next of "[".  Set the rewind
                 // offset to point to the beginning of "[". This has been
                 // explicitly tested with whitespace surrounding the array start
@@ -386,7 +385,7 @@ QPDFParser::parse(bool& empty, bool content_stream)
                     dict["/Contents"].setParsedOffset(frame.contents_offset);
                 }
                 object = QPDFObjectHandle::newDictionary(dict);
-                setDescription(object, offset, offset - 2);
+                setDescription(object, offset - 2);
                 // The `offset` points to the next of "<<". Set the rewind
                 // offset to point to the beginning of "<<". This has been
                 // explicitly tested with whitespace surrounding the dictionary
@@ -407,22 +406,16 @@ QPDFParser::parse(bool& empty, bool content_stream)
         object = QPDFObjectHandle::newNull();
     }
     if (!set_offset) {
-        setDescription(object, offset, offset);
+        setDescription(object, offset);
     }
     return object;
 }
 
 void
-QPDFParser::setDescription(
-    QPDFObjectHandle oh,
-    qpdf_offset_t descr_offset,
-    qpdf_offset_t parsed_offset) const
+QPDFParser::setDescription(QPDFObjectHandle oh, qpdf_offset_t parsed_offset)
 {
     if (auto& obj = oh.obj) {
-        auto descr = std::make_shared<std::string>(
-            input->getName() + ", " + object_description + " at offset " +
-            std::to_string(descr_offset));
-        obj->setDescription(context, descr, parsed_offset);
+        obj->setDescription(context, description, parsed_offset);
     }
 }
 
diff --git a/libqpdf/qpdf/QPDFParser.hh b/libqpdf/qpdf/QPDFParser.hh
index 28768df2..02ae83ed 100644
--- a/libqpdf/qpdf/QPDFParser.hh
+++ b/libqpdf/qpdf/QPDFParser.hh
@@ -20,7 +20,9 @@ class QPDFParser
         object_description(object_description),
         tokenizer(tokenizer),
         decrypter(decrypter),
-        context(context)
+        context(context),
+        description(std::make_shared<std::string>(
+            input->getName() + ", " + object_description + " at offset $PO"))
     {
     }
     virtual ~QPDFParser() = default;
@@ -40,15 +42,13 @@ class QPDFParser
     void warn(qpdf_offset_t offset, std::string const& msg) const;
     void warn(std::string const& msg) const;
     static void warn(QPDF*, QPDFExc const&);
-    void setDescription(
-        QPDFObjectHandle oh,
-        qpdf_offset_t descr_offset,
-        qpdf_offset_t parsed_offset = -1) const;
+    void setDescription(QPDFObjectHandle oh, qpdf_offset_t parsed_offset);
     std::shared_ptr<InputSource> input;
     std::string const& object_description;
     QPDFTokenizer& tokenizer;
     QPDFObjectHandle::StringDecrypter* decrypter;
     QPDF* context;
+    std::shared_ptr<std::string> description;
 };
 
 #endif // QPDFPARSER_HH
diff --git a/libqpdf/qpdf/QPDFValue.hh b/libqpdf/qpdf/QPDFValue.hh
index c7e63d6c..2d3b9de3 100644
--- a/libqpdf/qpdf/QPDFValue.hh
+++ b/libqpdf/qpdf/QPDFValue.hh
@@ -52,6 +52,13 @@ class QPDFValue
         if (auto pos = description.find("$OG"); pos != std::string::npos) {
             description.replace(pos, 3, og.unparse(' '));
         }
+        if (auto pos = description.find("$PO"); pos != std::string::npos) {
+            qpdf_offset_t shift = (type_code == ::ot_dictionary) ? 2
+                : (type_code == ::ot_array)                      ? 1
+                                                                 : 0;
+
+            description.replace(pos, 3, std::to_string(parsed_offset + shift));
+        }
         return qpdf != nullptr;
     }
     bool
-- 
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