From 306e809332f328117563e3446fd6d240e2adc112 Mon Sep 17 00:00:00 2001
From: m-holger <m.holger@qpdf.org>
Date: Thu, 16 Oct 2025 02:13:46 +0100
Subject: [PATCH] Refactor linearization data: encapsulate `first_xref_item_offset` and `uncompressed_after_compressed` in `QPDF::Doc::Objects`, update usage in `QPDF_linearization`, and streamline related logic.

---
 libqpdf/QPDF_linearization.cc |  6 +++---
 libqpdf/QPDF_objects.cc       |  6 +++---
 libqpdf/qpdf/QPDF_private.hh  | 23 ++++++++++++++++++-----
 3 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/libqpdf/QPDF_linearization.cc b/libqpdf/QPDF_linearization.cc
index 6bc128a..dfeb2dc 100644
--- a/libqpdf/QPDF_linearization.cc
+++ b/libqpdf/QPDF_linearization.cc
@@ -713,10 +713,10 @@ Lin::checkLinearizationInternal()
             break;
         }
     }
-    if (m->file->tell() != m->first_xref_item_offset) {
+    if (m->file->tell() != objects.first_xref_item_offset()) {
         linearizationWarning(
             "space before first xref item (/T) mismatch (computed = " +
-            std::to_string(m->first_xref_item_offset) +
+            std::to_string(objects.first_xref_item_offset()) +
             "; file = " + std::to_string(m->file->tell()));
     }
 
@@ -727,7 +727,7 @@ Lin::checkLinearizationInternal()
     // compressed objects are supposed to be at the end of the containing xref section if any object
     // streams are in use.
 
-    if (m->uncompressed_after_compressed) {
+    if (objects.uncompressed_after_compressed()) {
         linearizationWarning(
             "linearized file contains an uncompressed object after a compressed "
             "one in a cross-reference stream");
diff --git a/libqpdf/QPDF_objects.cc b/libqpdf/QPDF_objects.cc
index a9e8b27..cd8a849 100644
--- a/libqpdf/QPDF_objects.cc
+++ b/libqpdf/QPDF_objects.cc
@@ -694,7 +694,7 @@ Objects::read_xrefTable(qpdf_offset_t xref_offset)
         for (qpdf_offset_t i = obj; i - num < obj; ++i) {
             if (i == 0) {
                 // This is needed by checkLinearization()
-                m->first_xref_item_offset = m->file->tell();
+                first_xref_item_offset_ = m->file->tell();
             }
             // For xref_table, these will always be small enough to be ints
             qpdf_offset_t f1 = 0;
@@ -956,14 +956,14 @@ Objects::processXRefStream(
             // object record, in which case the generation number appears as the third field.
             if (saw_first_compressed_object) {
                 if (fields[0] != 2) {
-                    m->uncompressed_after_compressed = true;
+                    uncompressed_after_compressed_ = true;
                 }
             } else if (fields[0] == 2) {
                 saw_first_compressed_object = true;
             }
             if (obj == 0) {
                 // This is needed by checkLinearization()
-                m->first_xref_item_offset = xref_offset;
+                first_xref_item_offset_ = xref_offset;
             } else if (fields[0] == 0) {
                 // Ignore fields[2], which we don't care about in this case. This works around the
                 // issue of some PDF files that put invalid values, like -1, here for deleted
diff --git a/libqpdf/qpdf/QPDF_private.hh b/libqpdf/qpdf/QPDF_private.hh
index c184262..79efe70 100644
--- a/libqpdf/qpdf/QPDF_private.hh
+++ b/libqpdf/qpdf/QPDF_private.hh
@@ -323,6 +323,7 @@ class QPDF::Doc
 
         qpdf::Doc::Config& cf;
         QPDF::Doc::Pages& pages;
+        QPDF::Doc::Objects& objects;
     };
 
     Doc() = delete;
@@ -957,6 +958,17 @@ class QPDF::Doc::Objects: Common
         return streams_;
     }
 
+    // actual value from file
+    qpdf_offset_t
+    first_xref_item_offset() const
+    {
+        return first_xref_item_offset_;
+    }
+    bool
+    uncompressed_after_compressed() const
+    {
+        return uncompressed_after_compressed_;
+    }
     void parse(char const* password);
     std::shared_ptr<QPDFObject> const& resolve(QPDFObjGen og);
     void inParse(bool);
@@ -1028,6 +1040,10 @@ class QPDF::Doc::Objects: Common
 
     Foreign foreign_;
     Streams streams_;
+
+    // Linearization data
+    qpdf_offset_t first_xref_item_offset_{0}; // actual value from file
+    bool uncompressed_after_compressed_{false};
 }; // class QPDF::Doc::Objects
 
 // This class is used to represent a PDF Pages tree.
@@ -1172,10 +1188,6 @@ class QPDF::Members: Doc
     bool in_parse{false};
     bool parsed{false};
     std::set<int> resolved_object_streams;
-
-    // Linearization data
-    qpdf_offset_t first_xref_item_offset{0}; // actual value from file
-    bool uncompressed_after_compressed{false};
 };
 
 // The Resolver class is restricted to QPDFObject and BaseHandle so that only it can resolve
@@ -1197,7 +1209,8 @@ inline QPDF::Doc::Common::Common(QPDF& qpdf, QPDF::Members* m) :
     qpdf(qpdf),
     m(m),
     cf(m->cf),
-    pages(m->pages)
+    pages(m->pages),
+    objects(m->objects)
 {
 }
 
--
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