From 7b3427502a6b469120f8eee0cf6dc5f9c3315c23 Mon Sep 17 00:00:00 2001
From: m-holger <m.holger@qpdf.org>
Date: Sat, 19 Jul 2025 18:32:35 +0100
Subject: [PATCH] Refactor `QPDFWriter` to replace `pl::Link` with direct use of `Pipeline` for improved clarity and reduced indirection in pipeline management.

---
 libqpdf/QPDFWriter.cc            | 10 ++++------
 libqpdf/qpdf/Pipeline_private.hh | 39 +++++----------------------------------
 2 files changed, 9 insertions(+), 40 deletions(-)

diff --git a/libqpdf/QPDFWriter.cc b/libqpdf/QPDFWriter.cc
index 26b18ec..ba52fd9 100644
--- a/libqpdf/QPDFWriter.cc
+++ b/libqpdf/QPDFWriter.cc
@@ -141,7 +141,7 @@ namespace
         }
 
         void
-        activate(Popper& pp, std::unique_ptr<pl::Link> link)
+        activate(Popper& pp, std::unique_ptr<Pipeline> link)
         {
             count_buffer.clear();
             activate(pp, false, &count_buffer, std::move(link));
@@ -151,7 +151,7 @@ namespace
         activate(
             bool discard = false,
             std::string* str = nullptr,
-            std::unique_ptr<pl::Link> link = nullptr)
+            std::unique_ptr<Pipeline> link = nullptr)
         {
             Popper pp{*this};
             activate(pp, discard, str, std::move(link));
@@ -163,7 +163,7 @@ namespace
             Popper& pp,
             bool discard = false,
             std::string* str = nullptr,
-            std::unique_ptr<pl::Link> link = nullptr)
+            std::unique_ptr<Pipeline> link = nullptr)
         {
             std::unique_ptr<pl::Count> c;
             if (link) {
@@ -2735,9 +2735,7 @@ QPDFWriter::writeLinearized()
                 lin_pass1_file = QUtil::safe_fopen(m->lin_pass1_filename.c_str(), "wb");
                 m->pipeline_stack.activate(
                     pp_pass1,
-                    std::make_unique<pl::Link>(
-                        nullptr,
-                        std::make_unique<Pl_StdioFile>("linearization pass1", lin_pass1_file)));
+                    std::make_unique<Pl_StdioFile>("linearization pass1", lin_pass1_file));
             } else {
                 m->pipeline_stack.activate(pp_pass1, true);
             }
diff --git a/libqpdf/qpdf/Pipeline_private.hh b/libqpdf/qpdf/Pipeline_private.hh
index 2bc5872..c19dd41 100644
--- a/libqpdf/qpdf/Pipeline_private.hh
+++ b/libqpdf/qpdf/Pipeline_private.hh
@@ -8,35 +8,6 @@
 
 namespace qpdf::pl
 {
-    struct Link
-    {
-        Link(std::unique_ptr<Link> next_link, std::unique_ptr<Pipeline> next_pl) :
-            next_link(std::move(next_link)),
-            next_pl(std::move(next_pl))
-        {
-        }
-
-        std::unique_ptr<Link> next_link{nullptr};
-        std::unique_ptr<Pipeline> next_pl{nullptr};
-    };
-
-    template <typename P, typename... Args>
-    std::unique_ptr<Link>
-    create(Args&&... args)
-    {
-        return std::make_unique<Link>(
-            nullptr, std::make_unique<P>("", nullptr, std::forward<Args>(args)...));
-    }
-
-    template <typename P, typename... Args>
-    std::unique_ptr<Link>
-    create(std::unique_ptr<Link> link, Args&&... args)
-    {
-        auto* next = link->next_pl.get();
-        return std::make_unique<Link>(
-            std::move(link), std::make_unique<P>("", next, std::forward<Args>(args)...));
-    }
-
     class String final: public Pipeline
     {
       public:
@@ -85,8 +56,8 @@ namespace qpdf::pl
 
         // Count the number of characters written. If 'next' is not set, the content written will be
         // discarded.
-        Count(unsigned long id, std::unique_ptr<Link> link) :
-            Pipeline("", link ? link->next_pl.get() : nullptr),
+        Count(unsigned long id, std::unique_ptr<Pipeline> link) :
+            Pipeline("", link ? link.get() : nullptr),
             link(std::move(link)),
             id_(id),
             pass_immediately_to_next(link)
@@ -95,8 +66,8 @@ namespace qpdf::pl
 
         // Write to 'str'. If 'next' is set, 'str' will be written to 'next' when 'finish' is
         // called.
-        Count(unsigned long id, std::string& str, std::unique_ptr<Link> link = nullptr) :
-            Pipeline("", link ? link->next_pl.get() : nullptr),
+        Count(unsigned long id, std::string& str, std::unique_ptr<Pipeline> link = nullptr) :
+            Pipeline("", link ? link.get() : nullptr),
             str(&str),
             link(std::move(link)),
             id_(id)
@@ -169,7 +140,7 @@ namespace qpdf::pl
       private:
         qpdf_offset_t count{0};
         std::string* str{nullptr};
-        std::unique_ptr<Link> link{nullptr};
+        std::unique_ptr<Pipeline> link{nullptr};
         unsigned long id_{0};
         bool pass_immediately_to_next{false};
     };
--
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