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

@@ -4,13 +4,13 @@
 
 #include <algorithm>
 #include <atomic>
+#include <cstdlib>
+#include <cstring>
 #include <limits>
 #include <map>
 #include <memory.h>
 #include <regex>
 #include <sstream>
-#include <cstdlib>
-#include <cstring>
 #include <vector>
 
 #include <qpdf/BufferInputSource.hh>
@@ -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();
         }
     }
 
@@ -2528,9 +2533,7 @@ QPDF::getCompressibleObjGens()
         if (obj.isStream()) {
             QPDFObjectHandle dict = obj.getDict();
             std::set<std::string> keys = dict.getKeys();
-            for (auto iter = keys.rbegin();
-                 iter != keys.rend();
-                 ++iter) {
+            for (auto iter = keys.rbegin(); iter != keys.rend(); ++iter) {
                 std::string const& key = *iter;
                 QPDFObjectHandle value = dict.getKey(key);
                 if (key == "/Length") {
@@ -2544,9 +2547,7 @@ QPDF::getCompressibleObjGens()
             }
         } else if (obj.isDictionary()) {
             std::set<std::string> keys = obj.getKeys();
-            for (auto iter = keys.rbegin();
-                 iter != keys.rend();
-                 ++iter) {
+            for (auto iter = keys.rbegin(); iter != keys.rend(); ++iter) {
                 queue.push_front(obj.getKey(*iter));
             }
         } else if (obj.isArray()) {

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