Add Pl_Function -- a generic function pipeline

2 files changed, 78 insertions, 5 deletions

diff --git a/include/qpdf/Pl_Function.hh b/include/qpdf/Pl_Function.hh
new file mode 100644
index 00000000..dd700e80
--- /dev/null
+++ b/include/qpdf/Pl_Function.hh
@@ -0,0 +1,73 @@
+// Copyright (c) 2005-2022 Jay Berkenbilt
+//
+// This file is part of qpdf.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Versions of qpdf prior to version 7 were released under the terms
+// of version 2.0 of the Artistic License. At your option, you may
+// continue to consider qpdf to be licensed under those terms. Please
+// see the manual for additional information.
+
+#ifndef PL_FUNCTION_HH
+#define PL_FUNCTION_HH
+
+// This pipeline calls an arbitrary function with whatever data is
+// passed to it. This pipeline can be reused.
+//
+// For this pipeline, "next" may be null. If a next pointer is
+// provided, this pipeline will also pass the data through to it and
+// will forward finish() to it.
+//
+// It is okay to not call finish() on this pipeline if it has no
+// "next".
+
+#include <qpdf/Pipeline.hh>
+
+#include <functional>
+
+class QPDF_DLL_CLASS Pl_Function: public Pipeline
+{
+  public:
+    typedef std::function<void(unsigned char const*, size_t)> writer_t;
+
+    QPDF_DLL
+    Pl_Function(char const* identifier, Pipeline* next, writer_t fn);
+    QPDF_DLL
+    virtual ~Pl_Function();
+
+    QPDF_DLL
+    virtual void write(unsigned char const* buf, size_t len);
+    QPDF_DLL
+    virtual void finish();
+
+  private:
+    class QPDF_DLL_PRIVATE Members
+    {
+        friend class Pl_Function;
+
+      public:
+        QPDF_DLL
+        ~Members() = default;
+
+      private:
+        Members(writer_t);
+        Members(Members const&) = delete;
+
+        writer_t fn;
+    };
+
+    std::shared_ptr<Members> m;
+};
+
+#endif // PL_FUNCTION_HH
diff --git a/include/qpdf/Pl_String.hh b/include/qpdf/Pl_String.hh
index 327598da..906a2660 100644
--- a/include/qpdf/Pl_String.hh
+++ b/include/qpdf/Pl_String.hh
@@ -30,11 +30,11 @@
 // provided, this pipeline will also pass the data through to it and
 // will forward finish() to it.
 //
-// It is okay to not call finish() on this pipeline. This makes it
-// easy to stick this in front of another pipeline to capture data
-// that is written to the other pipeline without interfering with when
-// finish is called on the other pipeline and without having to put a
-// Pl_Concatenate after it.
+// It is okay to not call finish() on this pipeline if it has no
+// "next". This makes it easy to stick this in front of another
+// pipeline to capture data that is written to the other pipeline
+// without interfering with when finish is called on the other
+// pipeline and without having to put a Pl_Concatenate after it.
 
 #include <qpdf/Pipeline.hh>