From 5c1a5d433f1566dc1a75c261c372d87204810932 Mon Sep 17 00:00:00 2001
From: m-holger <m.holger@qpdf.org>
Date: Sat, 10 May 2025 13:25:06 +0100
Subject: [PATCH] I SF_FlateLzwDecode switch from shared_ptr to unique_ptr for pipeline management

---
 libqpdf/SF_FlateLzwDecode.cc      | 31 ++++++++++---------------------
 libqpdf/qpdf/SF_FlateLzwDecode.hh | 14 +++++++++++---
 2 files changed, 21 insertions(+), 24 deletions(-)

diff --git a/libqpdf/SF_FlateLzwDecode.cc b/libqpdf/SF_FlateLzwDecode.cc
index 433d585..bd5454d 100644
--- a/libqpdf/SF_FlateLzwDecode.cc
+++ b/libqpdf/SF_FlateLzwDecode.cc
@@ -69,48 +69,37 @@ SF_FlateLzwDecode::setDecodeParms(QPDFObjectHandle decode_parms)
 Pipeline*
 SF_FlateLzwDecode::getDecodePipeline(Pipeline* next)
 {
-    std::shared_ptr<Pipeline> pipeline;
+    std::unique_ptr<Pipeline> pipeline;
     if (predictor >= 10 && predictor <= 15) {
         QTC::TC("qpdf", "SF_FlateLzwDecode PNG filter");
-        pipeline = std::make_shared<Pl_PNGFilter>(
+        pipeline = std::make_unique<Pl_PNGFilter>(
             "png decode",
             next,
             Pl_PNGFilter::a_decode,
             QIntC::to_uint(columns),
             QIntC::to_uint(colors),
             QIntC::to_uint(bits_per_component));
-        pipelines.push_back(pipeline);
         next = pipeline.get();
+        pipelines.push_back(std::move(pipeline));
     } else if (predictor == 2) {
         QTC::TC("qpdf", "SF_FlateLzwDecode TIFF predictor");
-        pipeline = std::make_shared<Pl_TIFFPredictor>(
+        pipeline = std::make_unique<Pl_TIFFPredictor>(
             "tiff decode",
             next,
             Pl_TIFFPredictor::a_decode,
             QIntC::to_uint(columns),
             QIntC::to_uint(colors),
             QIntC::to_uint(bits_per_component));
-        pipelines.push_back(pipeline);
         next = pipeline.get();
+        pipelines.push_back(std::move(pipeline));
     }
 
     if (lzw) {
-        pipeline = std::make_shared<Pl_LZWDecoder>("lzw decode", next, early_code_change);
+        pipeline = std::make_unique<Pl_LZWDecoder>("lzw decode", next, early_code_change);
     } else {
-        pipeline = std::make_shared<Pl_Flate>("stream inflate", next, Pl_Flate::a_inflate);
+        pipeline = std::make_unique<Pl_Flate>("stream inflate", next, Pl_Flate::a_inflate);
     }
-    pipelines.push_back(pipeline);
-    return pipeline.get();
-}
-
-std::shared_ptr<QPDFStreamFilter>
-SF_FlateLzwDecode::flate_factory()
-{
-    return std::make_shared<SF_FlateLzwDecode>(false);
-}
-
-std::shared_ptr<QPDFStreamFilter>
-SF_FlateLzwDecode::lzw_factory()
-{
-    return std::make_shared<SF_FlateLzwDecode>(true);
+    next = pipeline.get();
+    pipelines.push_back(std::move(pipeline));
+    return next;
 }
diff --git a/libqpdf/qpdf/SF_FlateLzwDecode.hh b/libqpdf/qpdf/SF_FlateLzwDecode.hh
index 4b70b50..9244adc 100644
--- a/libqpdf/qpdf/SF_FlateLzwDecode.hh
+++ b/libqpdf/qpdf/SF_FlateLzwDecode.hh
@@ -17,8 +17,16 @@ class SF_FlateLzwDecode final: public QPDFStreamFilter
     bool setDecodeParms(QPDFObjectHandle decode_parms) final;
     Pipeline* getDecodePipeline(Pipeline* next) final;
 
-    static std::shared_ptr<QPDFStreamFilter> flate_factory();
-    static std::shared_ptr<QPDFStreamFilter> lzw_factory();
+    static std::shared_ptr<QPDFStreamFilter>
+    flate_factory()
+    {
+        return std::make_shared<SF_FlateLzwDecode>(false);
+    }
+    static std::shared_ptr<QPDFStreamFilter>
+    lzw_factory()
+    {
+        return std::make_shared<SF_FlateLzwDecode>(true);
+    }
 
   private:
     bool lzw{};
@@ -28,7 +36,7 @@ class SF_FlateLzwDecode final: public QPDFStreamFilter
     int colors{1};
     int bits_per_component{8};
     bool early_code_change{true};
-    std::vector<std::shared_ptr<Pipeline>> pipelines;
+    std::vector<std::unique_ptr<Pipeline>> pipelines;
 };
 
 #endif // SF_FLATELZWDECODE_HH
--
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