Add getBufferSharedPointer() to Pl_Buffer and QPDFWriter

ChangeLog

@@ -1,5 +1,9 @@
 2022-02-06  Jay Berkenbilt  <ejb@ql.org>
 
+	* Pl_Buffer and QPDFWriter: add getBufferSharedPointer(), which
+	turns a PointerHolder<Buffer> but will return a
+	std::shared_ptr<Buffer> in qpdf 11.
+
 	* From m-holger: add getKeyIfDict(), which calls getKey for
 	dictionaries and returns null if called on null. This is for
 	easier access to optional, lower-level dictionaries.

TODO

@@ -420,6 +420,8 @@ auto x = std::make_unique<T[]>(5)
 
 PointerHolder in public API:
 
+  PointerHolder<Buffer> Pl_Buffer::getBufferSharedPointer();
+  PointerHolder<Buffer> QPDFWriter::getBufferSharedPointer();
   QUtil::read_file_into_memory(
     char const*, PointerHolder<char>&, unsigned long&)
   QPDFObjectHandle::addContentTokenFilter(

include/qpdf/Pl_Buffer.hh

@@ -51,10 +51,14 @@ class Pl_Buffer: public Pipeline
 
     // Each call to getBuffer() resets this object -- see notes above.
     // The caller is responsible for deleting the returned Buffer
-    // object.
+    // object. See also getBufferSharedPointer() and getMallocBuffer().
     QPDF_DLL
     Buffer* getBuffer();
 
+    // Same as getBuffer but wraps the result in a shared pointer.
+    QPDF_DLL
+    PointerHolder<Buffer> getBufferSharedPointer();
+
     // getMallocBuffer behaves in the same was as getBuffer except the
     // buffer is allocated with malloc(), making it suitable for use
     // when calling from other languages. If there is no data, *buf is

include/qpdf/QPDFWriter.hh

@@ -118,13 +118,18 @@ class QPDFWriter
     QPDF_DLL
     void setOutputMemory();
 
-    // Return the buffer object containing the PDF file.  If
+    // Return the buffer object containing the PDF file. If
     // setOutputMemory() has been called, this method may be called
-    // exactly one time after write() has returned.  The caller is
-    // responsible for deleting the buffer when done.
+    // exactly one time after write() has returned. The caller is
+    // responsible for deleting the buffer when done. See also
+    // getBufferSharedPointer().
     QPDF_DLL
     Buffer* getBuffer();
 
+    // Return getBuffer() in a shared pointer.
+    QPDF_DLL
+    PointerHolder<Buffer> getBufferSharedPointer();
+
     // Supply your own pipeline object.  Output will be written to
     // this pipeline, and QPDFWriter will call finish() on the
     // pipeline.  It is the caller's responsibility to manage the

libqpdf/Pl_Buffer.cc

@@ -79,10 +79,16 @@ Pl_Buffer::getBuffer()
         unsigned char* p = b->getBuffer();
         memcpy(p, this->m->data->getBuffer(), this->m->total_size);
     }
-    this->m = new Members();
+    this->m = PointerHolder<Members>(new Members());
     return b;
 }
 
+PointerHolder<Buffer>
+Pl_Buffer::getBufferSharedPointer()
+{
+    return PointerHolder<Buffer>(getBuffer());
+}
+
 void
 Pl_Buffer::getMallocBuffer(unsigned char **buf, size_t* len)
 {

libqpdf/QPDFWriter.cc

@@ -157,6 +157,12 @@ QPDFWriter::getBuffer()
     return result;
 }
 
+PointerHolder<Buffer>
+QPDFWriter::getBufferSharedPointer()
+{
+    return PointerHolder<Buffer>(getBuffer());
+}
+
 void
 QPDFWriter::setOutputPipeline(Pipeline* p)
 {