Merge pull request #1582 from m-holger/null

Add private-API Null class

Merge pull request #1582 from m-holger/null
Add private-API Null class
m-holger · GitHub
2 parents 6a0d6fe1 2d11e4dd
Showing 7 changed files with 45 additions and 19 deletions
libqpdf/QPDFAcroFormDocumentHelper.cc
libqpdf/QPDFAnnotationObjectHelper.cc
libqpdf/QPDFEmbeddedFileDocumentHelper.cc
libqpdf/QPDFFileSpecObjectHelper.cc
libqpdf/QPDFObjectHandle.cc
libqpdf/qpdf/QPDFObjectHandle_private.hh
qpdf/qpdf.testcov
@@ -252,16 +252,15 @@ QPDFFormFieldObjectHelper
 QPDFAcroFormDocumentHelper::getFieldForAnnotation(QPDFAnnotationObjectHelper h)
 {
     QPDFObjectHandle oh = h.getObjectHandle();
-    QPDFFormFieldObjectHelper result(QPDFObjectHandle::newNull());
     if (!oh.isDictionaryOfType("", "/Widget")) {
-        return result;
+        return Null::temp();
     }
     analyze();
     QPDFObjGen og(oh.getObjGen());
     if (m->annotation_to_field.contains(og)) {
-        result = m->annotation_to_field[og];
+        return m->annotation_to_field[og];
     }
-    return result;
+    return Null::temp();
 }
  
 void
@@ -56,20 +56,16 @@ QPDFAnnotationObjectHelper::getAppearanceStream(std::string const&amp; which, std::s
             // appearance stream when /AP is a dictionary, but files have been seen in the wild
             // where Appearance State is `/N` and `/AP` is a stream. Therefore, if `which` points to
             // a stream, disregard state and just use the stream. See qpdf issue #949 for details.
-            QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP stream");
             return ap_sub;
         }
-        if (ap_sub.isDictionary() && (!desired_state.empty())) {
-            QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP dictionary");
+        if (ap_sub.isDictionary() && !desired_state.empty()) {
             QPDFObjectHandle ap_sub_val = ap_sub.getKey(desired_state);
             if (ap_sub_val.isStream()) {
-                QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP sub stream");
                 return ap_sub_val;
             }
         }
     }
-    QTC::TC("qpdf", "QPDFAnnotationObjectHelper AP null");
-    return QPDFObjectHandle::newNull();
+    return Null::temp();
 }
  
 std::string
 #include <qpdf/QPDFEmbeddedFileDocumentHelper.hh>
  
 #include <qpdf/QPDFNameTreeObjectHelper.hh>
+#include <qpdf/QPDFObjectHandle_private.hh>
 #include <qpdf/QPDF_private.hh>
  
 // File attachments are stored in the /EmbeddedFiles (name tree) key of the /Names dictionary from
@@ -143,11 +144,10 @@ QPDFEmbeddedFileDocumentHelper::removeEmbeddedFile(std::string const&amp; name)
     if (iter == m->embedded_files->end()) {
         return false;
     }
-    auto oh = iter->second;
-    iter.remove();
-    if (oh.isIndirect()) {
-        qpdf.replaceObject(oh.getObjGen(), QPDFObjectHandle::newNull());
+    if (iter->second.indirect()) {
+        qpdf.replaceObject(iter->second, Null());
     }
+    iter.remove();
  
     return true;
 }
@@ -76,7 +76,7 @@ QPDFFileSpecObjectHelper::getEmbeddedFileStream(std::string const&amp; key)
             }
         }
     }
-    return QPDFObjectHandle::newNull();
+    return Null::temp();
 }
  
 QPDFObjectHandle
@@ -25,6 +25,8 @@
 using namespace std::literals;
 using namespace qpdf;
  
+const Null Null::temp_;
+
 BaseHandle::
 operator QPDFObjGen() const
 {
@@ -468,6 +468,39 @@ namespace qpdf
         }
     };
  
+    class Null final: public BaseHandle
+    {
+      public:
+        // Unlike other types, the Null default constructor creates a valid null object.
+        Null() :
+            BaseHandle(QPDFObject::create<QPDF_Null>())
+        {
+        }
+
+        Null(Null const&) = default;
+        Null(Null&&) = default;
+        Null& operator=(Null const&) = default;
+        Null& operator=(Null&&) = default;
+        ~Null() = default;
+
+        // For legacy support, return a Null object to be used as a temporary return value.
+        static QPDFObjectHandle
+        temp()
+        {
+            return temp_.oh();
+        }
+
+        // For legacy support, return an explicit temporary Null object if oh is null.
+        static QPDFObjectHandle
+        if_null(QPDFObjectHandle oh)
+        {
+            return oh ? std::move(oh) : Null::temp();
+        }
+
+      private:
+        static const Null temp_;
+    }; // class Null
+
     class Stream final: public BaseHandle
     {
       public:
@@ -181,10 +181,6 @@ QPDFFormFieldObjectHelper TU absent 0
 QPDFFormFieldObjectHelper TM absent 0
 QPDFFormFieldObjectHelper Q present 1
 QPDFFormFieldObjectHelper DA present 1
-QPDFAnnotationObjectHelper AP stream 0
-QPDFAnnotationObjectHelper AP dictionary 0
-QPDFAnnotationObjectHelper AP sub stream 0
-QPDFAnnotationObjectHelper AP null 0
 QPDFAcroFormDocumentHelper field found 1
 QPDFAcroFormDocumentHelper annotation found 1
 QPDFJob automatically set keep files open 1