Merge pull request #959 from m-holger/reserved

Add new method QPDF::newReserved()

include/qpdf/QPDF.hh

@@ -413,6 +413,24 @@ class QPDF
     QPDF_DLL
     QPDFObjectHandle newStream(std::string const& data);
 
+    // A reserved object is a special sentinel used for qpdf to
+    // reserve a spot for an object that is going to be added to the
+    // QPDF object.  Normally you don't have to use this type since
+    // you can just call QPDF::makeIndirectObject.  However, in some
+    // cases, if you have to create objects with circular references,
+    // you may need to create a reserved object so that you can have a
+    // reference to it and then replace the object later.  Reserved
+    // objects have the special property that they can't be resolved
+    // to direct objects.  This makes it possible to replace a
+    // reserved object with a new object while preserving existing
+    // references to them.  When you are ready to replace a reserved
+    // object with its replacement, use QPDF::replaceReserved for this
+    // purpose rather than the more general QPDF::replaceObject.  It
+    // is an error to try to write a QPDF with QPDFWriter if it has
+    // any reserved objects in it.
+    QPDF_DLL
+    QPDFObjectHandle newReserved();
+
     // Install this object handle as an indirect object and return an
     // indirect reference to it.
     QPDF_DLL

include/qpdf/QPDFObjectHandle.hh

@@ -668,7 +668,8 @@ class QPDFObjectHandle
     // object with its replacement, use QPDF::replaceReserved for this
     // purpose rather than the more general QPDF::replaceObject.  It
     // is an error to try to write a QPDF with QPDFWriter if it has
-    // any reserved objects in it.
+    // any reserved objects in it. From QPDF 11.4, you can
+    // call QPDF::newReserved() instead.
     QPDF_DLL
     static QPDFObjectHandle newReserved(QPDF* qpdf);
 

libqpdf/QPDF.cc

@@ -1984,6 +1984,12 @@ QPDF::makeIndirectObject(QPDFObjectHandle oh)
     return makeIndirectFromQPDFObject(oh.getObj());
 }
 
+QPDFObjectHandle
+QPDF::newReserved()
+{
+    return makeIndirectFromQPDFObject(QPDF_Reserved::create());
+}
+
 QPDFObjectHandle
 QPDF::newStream()
 {
@@ -2207,9 +2213,8 @@ QPDF::reserveObjects(QPDFObjectHandle foreign, ObjCopier& obj_copier, bool top)
         QTC::TC("qpdf", "QPDF copy indirect");
         if (obj_copier.object_map.count(foreign_og) == 0) {
             obj_copier.to_copy.push_back(foreign);
-            obj_copier.object_map[foreign_og] = foreign.isStream()
-                ? newStream()
-                : QPDFObjectHandle::newReserved(this);
+            obj_copier.object_map[foreign_og] =
+                foreign.isStream() ? newStream() : newReserved();
         }
     }
 

libqpdf/QPDFObjectHandle.cc

@@ -2128,7 +2128,11 @@ QPDFObjectHandle::newStream(QPDF* qpdf, std::string const& data)
 QPDFObjectHandle
 QPDFObjectHandle::newReserved(QPDF* qpdf)
 {
-    return qpdf->makeIndirectObject(QPDFObjectHandle(QPDF_Reserved::create()));
+    if (qpdf == nullptr) {
+        throw std::runtime_error(
+            "attempt to create reserved object in null qpdf object");
+    }
+    return qpdf->newReserved();
 }
 
 void