mirror of https://github.com/qpdf/qpdf.git
Add concept of reserved objects
QPDFObjectHandle::{new,is,assert}Reserved, QPDF::replaceReserved
provide a mechanism to add objects to a PDF file when there are
circular references. This is a prerequisite to copying objects from
one PDF to another.
This commit is contained in:
Jay Berkenbilt
parent
af64668ad1
commit
8a217eb3a2
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@ -1,3 +1,12 @@
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2012-07-08 Jay Berkenbilt <ejb@ql.org>
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* Add QPDFObjectHandle::newReserved to create a reserved object
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and QPDF::replaceReserved to replace it with a real object.
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QPDFObjectHandle::newReserved reserves an object ID in a QPDF
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object and ensures that any references to it remain unresolved.
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When QPDF::replaceReserved is later called, previous references to
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the reserved object will properly resolve to the replaced object.
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2012-07-07 Jay Berkenbilt <ejb@ql.org>
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* NOTE: BREAKING API CHANGE. Remove previously required length
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@ -161,7 +161,8 @@ class QPDF
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// be associated with the PDF file. Note that replacing an object
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// with QPDFObjectHandle::newNull() effectively removes the object
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// from the file since a non-existent object is treated as a null
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// object.
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// object. To replace a reserved object, call replaceReserved
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// instead.
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QPDF_DLL
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void replaceObject(int objid, int generation, QPDFObjectHandle);
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@ -180,6 +181,15 @@ class QPDF
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void swapObjects(int objid1, int generation1,
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int objid2, int generation2);
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// Replace a reserved object. This is a wrapper around
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// replaceObject but it guarantees that the underlying object is a
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// reserved object. After this call, reserved will be a reference
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// to replacement.
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QPDF_DLL
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void
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replaceReserved(QPDFObjectHandle reserved,
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QPDFObjectHandle replacement);
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// Encryption support
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enum encryption_method_e { e_none, e_unknown, e_rc4, e_aes };
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@ -81,6 +81,8 @@ class QPDFObjectHandle
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bool isDictionary();
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QPDF_DLL
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bool isStream();
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QPDF_DLL
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bool isReserved();
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// This returns true in addition to the query for the specific
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// type for indirect objects.
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@ -148,6 +150,24 @@ class QPDFObjectHandle
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QPDF_DLL
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static QPDFObjectHandle newStream(QPDF* qpdf, std::string const& data);
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// A reserved object is a special sentinel used for qpdf to
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// reserve a spot for an object that is going to be added to the
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// QPDF object. Normally you don't have to use this type since
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// you can just call QPDF::makeIndirectObject. However, in some
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// cases, if you have to create objects with circular references,
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// you may need to create a reserved object so that you can have a
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// reference to it and then replace the object later. Reserved
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// objects have the special property that they can't be resolved
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// to direct objects. This makes it possible to replace a
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// reserved object with a new object while preserving existing
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// references to them. When you are ready to replace a reserved
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// object with its replacement, use QPDF::replaceReserved for this
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// purpose rather than the more general QPDF::replaceObject. It
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// is an error to try to write a QPDF with QPDFWriter if it has
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// any reserved objects in it.
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QPDF_DLL
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static QPDFObjectHandle newReserved(QPDF* qpdf);
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// Accessor methods. If an accessor method that is valid for only
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// a particular object type is called on an object of the wrong
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// type, an exception is thrown.
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@ -430,6 +450,8 @@ class QPDFObjectHandle
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void assertDictionary();
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QPDF_DLL
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void assertStream();
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QPDF_DLL
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void assertReserved();
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QPDF_DLL
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void assertScalar();
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@ -459,6 +481,7 @@ class QPDFObjectHandle
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int objid; // 0 for direct object
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int generation;
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PointerHolder<QPDFObject> obj;
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bool reserved;
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};
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#endif // __QPDFOBJECTHANDLE_HH__
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@ -2056,6 +2056,18 @@ QPDF::replaceObject(int objid, int generation, QPDFObjectHandle oh)
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ObjCache(QPDFObjectHandle::ObjAccessor::getObject(oh), -1, -1);
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}
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void
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QPDF::replaceReserved(QPDFObjectHandle reserved,
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QPDFObjectHandle replacement)
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{
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QTC::TC("qpdf", "QPDF replaceReserved");
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reserved.assertReserved();
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replaceObject(reserved.getObjectID(),
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reserved.getGeneration(),
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replacement);
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}
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void
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QPDF::swapObjects(int objid1, int generation1, int objid2, int generation2)
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{
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@ -10,6 +10,7 @@
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#include <qpdf/QPDF_Array.hh>
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#include <qpdf/QPDF_Dictionary.hh>
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#include <qpdf/QPDF_Stream.hh>
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#include <qpdf/QPDF_Reserved.hh>
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#include <qpdf/QTC.hh>
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#include <qpdf/QUtil.hh>
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@ -20,7 +21,8 @@
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QPDFObjectHandle::QPDFObjectHandle() :
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initialized(false),
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objid(0),
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generation(0)
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generation(0),
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reserved(false)
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{
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}
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@ -28,7 +30,8 @@ QPDFObjectHandle::QPDFObjectHandle(QPDF* qpdf, int objid, int generation) :
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initialized(true),
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qpdf(qpdf),
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objid(objid),
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generation(generation)
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generation(generation),
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reserved(false)
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{
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}
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@ -37,7 +40,8 @@ QPDFObjectHandle::QPDFObjectHandle(QPDFObject* data) :
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qpdf(0),
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objid(0),
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generation(0),
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obj(data)
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obj(data),
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reserved(false)
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{
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}
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@ -165,6 +169,14 @@ QPDFObjectHandle::isStream()
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return QPDFObjectTypeAccessor<QPDF_Stream>::check(obj.getPointer());
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}
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bool
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QPDFObjectHandle::isReserved()
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{
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// dereference will clear reserved if this has been replaced
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dereference();
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return this->reserved;
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}
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bool
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QPDFObjectHandle::isIndirect()
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{
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@ -568,6 +580,11 @@ QPDFObjectHandle::unparse()
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std::string
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QPDFObjectHandle::unparseResolved()
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{
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if (this->reserved)
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{
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throw std::logic_error(
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"QPDFObjectHandle: attempting to unparse a reserved object");
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}
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dereference();
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return this->obj->unparse();
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}
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@ -689,6 +706,19 @@ QPDFObjectHandle::newStream(QPDF* qpdf, std::string const& data)
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return QPDFObjectHandle::newStream(qpdf, b);
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}
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QPDFObjectHandle
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QPDFObjectHandle::newReserved(QPDF* qpdf)
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{
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// Reserve a spot for this object by assigning it an object
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// number, but then return an unresolved handle to the object.
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QPDFObjectHandle reserved = qpdf->makeIndirectObject(
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QPDFObjectHandle(new QPDF_Reserved()));
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QPDFObjectHandle result =
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newIndirect(qpdf, reserved.objid, reserved.generation);
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result.reserved = true;
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return result;
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}
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QPDFObjectHandle
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QPDFObjectHandle::shallowCopy()
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{
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@ -746,6 +776,13 @@ QPDFObjectHandle::makeDirectInternal(std::set<int>& visited)
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visited.insert(cur_objid);
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}
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if (isReserved())
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{
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throw std::logic_error(
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"QPDFObjectHandle: attempting to make a"
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" reserved object handle direct");
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}
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dereference();
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this->objid = 0;
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this->generation = 0;
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@ -902,6 +939,12 @@ QPDFObjectHandle::assertStream()
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assertType("Stream", isStream());
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}
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void
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QPDFObjectHandle::assertReserved()
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{
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assertType("Reserved", isReserved());
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}
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void
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QPDFObjectHandle::assertScalar()
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{
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@ -929,12 +972,21 @@ QPDFObjectHandle::dereference()
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{
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if (this->obj.getPointer() == 0)
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{
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this->obj = QPDF::Resolver::resolve(
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PointerHolder<QPDFObject> obj = QPDF::Resolver::resolve(
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this->qpdf, this->objid, this->generation);
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if (this->obj.getPointer() == 0)
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if (obj.getPointer() == 0)
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{
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QTC::TC("qpdf", "QPDFObjectHandle indirect to unknown");
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this->obj = new QPDF_Null();
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}
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else if (dynamic_cast<QPDF_Reserved*>(obj.getPointer()))
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{
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// Do not resolve
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}
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else
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{
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this->reserved = false;
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this->obj = obj;
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}
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}
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}
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@ -0,0 +1,13 @@
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#include <qpdf/QPDF_Reserved.hh>
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#include <stdexcept>
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QPDF_Reserved::~QPDF_Reserved()
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{
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}
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std::string
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QPDF_Reserved::unparse()
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{
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throw std::logic_error("attempt to unparse QPDF_Reserved");
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return "";
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}
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@ -39,6 +39,7 @@ SRCS_libqpdf = \
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libqpdf/QPDF_Name.cc \
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libqpdf/QPDF_Null.cc \
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libqpdf/QPDF_Real.cc \
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libqpdf/QPDF_Reserved.cc \
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libqpdf/QPDF_Stream.cc \
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libqpdf/QPDF_String.cc \
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libqpdf/QPDF_encryption.cc \
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@ -0,0 +1,13 @@
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#ifndef __QPDF_RESERVED_HH__
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#define __QPDF_RESERVED_HH__
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#include <qpdf/QPDFObject.hh>
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class QPDF_Reserved: public QPDFObject
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{
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public:
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virtual ~QPDF_Reserved();
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virtual std::string unparse();
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};
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#endif // __QPDF_RESERVED_HH__
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@ -217,3 +217,4 @@ QPDFObjectHandle newStream with string 0
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QPDF unknown key not inherited 0
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QPDF_Stream provider length not provided 0
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QPDF_Stream unknown stream length 0
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QPDF replaceReserved 0
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@ -149,7 +149,7 @@ $td->runtest("remove page we don't have",
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$td->NORMALIZE_NEWLINES);
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# ----------
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$td->notify("--- Miscellaneous Tests ---");
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$n_tests += 41;
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$n_tests += 43;
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$td->runtest("qpdf version",
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{$td->COMMAND => "qpdf --version"},
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@ -358,6 +358,13 @@ $td->runtest("warn for unknown key in Pages",
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{$td->COMMAND => "test_driver 23 lin-special.pdf"},
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{$td->FILE => "pages-warning.out", $td->EXIT_STATUS => 0},
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$td->NORMALIZE_NEWLINES);
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$td->runtest("reserved objects",
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{$td->COMMAND => "test_driver 24 minimal.pdf"},
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{$td->FILE => "reserved-objects.out", $td->EXIT_STATUS => 0},
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$td->NORMALIZE_NEWLINES);
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$td->runtest("check output",
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{$td->FILE => "a.pdf"},
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{$td->FILE => "reserved-objects.pdf"});
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show_ntests();
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# ----------
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@ -0,0 +1,8 @@
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res1 is still reserved after checking if array
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res1 is no longer reserved
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res1 is an array
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logic error: QPDFObjectHandle: attempting to unparse a reserved object
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logic error: QPDFObjectHandle: attempting to make a reserved object handle direct
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res2 is an array
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circular access and lazy resolution worked
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test 24 done
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@ -0,0 +1,48 @@
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%PDF-1.3
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%¿÷¢þ
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1 0 obj
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<< /Pages 4 0 R /Type /Catalog >>
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endobj
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2 0 obj
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[ 3 0 R 1 ]
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endobj
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3 0 obj
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[ 2 0 R 2 ]
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endobj
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4 0 obj
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<< /Count 1 /Kids [ 5 0 R ] /Type /Pages >>
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endobj
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5 0 obj
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<< /Contents 6 0 R /MediaBox [ 0 0 612 792 ] /Parent 4 0 R /Resources << /Font << /F1 7 0 R >> /ProcSet 8 0 R >> /Type /Page >>
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endobj
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6 0 obj
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<< /Length 44 >>
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stream
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BT
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/F1 24 Tf
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72 720 Td
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(Potato) Tj
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ET
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endstream
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endobj
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7 0 obj
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<< /BaseFont /Helvetica /Encoding /WinAnsiEncoding /Name /F1 /Subtype /Type1 /Type /Font >>
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endobj
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8 0 obj
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[ /PDF /Text ]
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endobj
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xref
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0 9
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0000000000 65535 f
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0000000015 00000 n
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0000000064 00000 n
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0000000091 00000 n
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0000000118 00000 n
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0000000177 00000 n
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0000000320 00000 n
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0000000413 00000 n
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0000000520 00000 n
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trailer << /Root 1 0 R /Size 9 Array1 2 0 R Array2 3 0 R /ID [<31415926535897932384626433832795><31415926535897932384626433832795>] >>
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startxref
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550
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%%EOF
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@ -840,6 +840,82 @@ void runtest(int n, char const* filename)
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std::vector<QPDFObjectHandle> const& pages = pdf.getAllPages();
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pdf.removePage(pages.back());
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}
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else if (n == 24)
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{
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// Test behavior of reserved objects
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QPDFObjectHandle res1 = QPDFObjectHandle::newReserved(&pdf);
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QPDFObjectHandle res2 = QPDFObjectHandle::newReserved(&pdf);
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QPDFObjectHandle trailer = pdf.getTrailer();
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trailer.replaceKey("Array1", res1);
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trailer.replaceKey("Array2", res2);
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QPDFObjectHandle array1 = QPDFObjectHandle::newArray();
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QPDFObjectHandle array2 = QPDFObjectHandle::newArray();
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array1.appendItem(res2);
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array1.appendItem(QPDFObjectHandle::newInteger(1));
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array2.appendItem(res1);
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array2.appendItem(QPDFObjectHandle::newInteger(2));
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// Make sure trying to ask questions about a reserved object
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// doesn't break it.
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if (res1.isArray())
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{
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std::cout << "oops -- res1 is an array" << std::endl;
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}
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if (res1.isReserved())
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{
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std::cout << "res1 is still reserved after checking if array"
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<< std::endl;
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}
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pdf.replaceReserved(res1, array1);
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if (res1.isReserved())
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{
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std::cout << "oops -- res1 is still reserved" << std::endl;
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}
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else
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{
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std::cout << "res1 is no longer reserved" << std::endl;
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}
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res1.assertArray();
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std::cout << "res1 is an array" << std::endl;
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try
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{
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res2.unparseResolved();
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std::cout << "oops -- didn't throw" << std::endl;
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}
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catch (std::logic_error e)
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{
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std::cout << "logic error: " << e.what() << std::endl;
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}
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try
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{
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res2.makeDirect();
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std::cout << "oops -- didn't throw" << std::endl;
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}
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catch (std::logic_error e)
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{
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std::cout << "logic error: " << e.what() << std::endl;
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}
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pdf.replaceReserved(res2, array2);
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res2.assertArray();
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std::cout << "res2 is an array" << std::endl;
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// Verify that the previously added reserved keys can be
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// dereferenced properly now
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int i1 = res1.getArrayItem(0).getArrayItem(1).getIntValue();
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int i2 = res2.getArrayItem(0).getArrayItem(1).getIntValue();
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if ((i1 == 2) && (i2 == 1))
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{
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std::cout << "circular access and lazy resolution worked" << std::endl;
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}
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QPDFWriter w(pdf, "a.pdf");
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w.setStaticID(true);
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w.setStreamDataMode(qpdf_s_preserve);
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w.write();
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}
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else
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{
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throw std::runtime_error(std::string("invalid test ") +
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