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a11549a566
Pushing inherited objects to pages and getting all pages were both prone to stack overflow infinite loops if there were loops in the Pages dictionary. There is a general weakness in the code in that any part of the code that traverses the Pages structure would be prone to this and would have to implement its own loop detection. A more robust fix may provide some general method for handling the Pages structure, but it's probably not worth doing. Note: addition of *Internal2 private functions was done rather than changing signatures of existing methods to avoid breaking compatibility.
496 lines
14 KiB
C++
496 lines
14 KiB
C++
// See the "Optimization" section of the manual.
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#include <qpdf/QPDF.hh>
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#include <qpdf/QTC.hh>
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#include <qpdf/QPDFExc.hh>
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#include <qpdf/QPDF_Dictionary.hh>
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#include <qpdf/QPDF_Array.hh>
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#include <assert.h>
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QPDF::ObjUser::ObjUser() :
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ou_type(ou_bad),
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pageno(0)
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{
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}
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QPDF::ObjUser::ObjUser(user_e type) :
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ou_type(type),
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pageno(0)
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{
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assert(type == ou_root);
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}
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QPDF::ObjUser::ObjUser(user_e type, int pageno) :
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ou_type(type),
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pageno(pageno)
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{
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assert((type == ou_page) || (type == ou_thumb));
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}
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QPDF::ObjUser::ObjUser(user_e type, std::string const& key) :
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ou_type(type),
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pageno(0),
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key(key)
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{
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assert((type == ou_trailer_key) || (type == ou_root_key));
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}
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bool
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QPDF::ObjUser::operator<(ObjUser const& rhs) const
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{
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if (this->ou_type < rhs.ou_type)
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{
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return true;
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}
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else if (this->ou_type == rhs.ou_type)
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{
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if (this->pageno < rhs.pageno)
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{
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return true;
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}
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else if (this->pageno == rhs.pageno)
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{
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return (this->key < rhs.key);
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}
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}
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return false;
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}
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void
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QPDF::optimize(std::map<int, int> const& object_stream_data,
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bool allow_changes)
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{
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if (! this->obj_user_to_objects.empty())
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{
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// already optimized
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return;
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}
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// The PDF specification indicates that /Outlines is supposed to
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// be an indirect reference. Force it to be so if it exists and
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// is direct. (This has been seen in the wild.)
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QPDFObjectHandle root = getRoot();
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if (root.getKey("/Outlines").isDictionary())
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{
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QPDFObjectHandle outlines = root.getKey("/Outlines");
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if (! outlines.isIndirect())
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{
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QTC::TC("qpdf", "QPDF_optimization indirect outlines");
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root.replaceKey("/Outlines", makeIndirectObject(outlines));
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}
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}
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// Traverse pages tree pushing all inherited resources down to the
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// page level. This also initializes this->all_pages.
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pushInheritedAttributesToPage(allow_changes, false);
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// Traverse pages
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int n = this->all_pages.size();
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for (int pageno = 0; pageno < n; ++pageno)
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{
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updateObjectMaps(ObjUser(ObjUser::ou_page, pageno),
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this->all_pages.at(pageno));
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}
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// Traverse document-level items
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std::set<std::string> keys = this->trailer.getKeys();
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for (std::set<std::string>::iterator iter = keys.begin();
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iter != keys.end(); ++iter)
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{
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std::string const& key = *iter;
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if (key == "/Root")
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{
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// handled separately
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}
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else
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{
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updateObjectMaps(ObjUser(ObjUser::ou_trailer_key, key),
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this->trailer.getKey(key));
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}
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}
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keys = root.getKeys();
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for (std::set<std::string>::iterator iter = keys.begin();
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iter != keys.end(); ++iter)
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{
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// Technically, /I keys from /Thread dictionaries are supposed
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// to be handled separately, but we are going to disregard
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// that specification for now. There is loads of evidence
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// that pdlin and Acrobat both disregard things like this from
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// time to time, so this is almost certain not to cause any
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// problems.
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std::string const& key = *iter;
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updateObjectMaps(ObjUser(ObjUser::ou_root_key, key),
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root.getKey(key));
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}
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ObjUser root_ou = ObjUser(ObjUser::ou_root);
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QPDFObjGen root_og = QPDFObjGen(root.getObjGen());
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obj_user_to_objects[root_ou].insert(root_og);
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object_to_obj_users[root_og].insert(root_ou);
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filterCompressedObjects(object_stream_data);
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}
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void
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QPDF::pushInheritedAttributesToPage()
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{
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// Public API should not have access to allow_changes.
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pushInheritedAttributesToPage(true, false);
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}
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void
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QPDF::pushInheritedAttributesToPage(bool allow_changes, bool warn_skipped_keys)
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{
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// Traverse pages tree pushing all inherited resources down to the
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// page level.
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// The record of whether we've done this is cleared by
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// updateAllPagesCache(). If we're warning for skipped keys,
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// re-traverse unconditionally.
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if (this->pushed_inherited_attributes_to_pages && (! warn_skipped_keys))
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{
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return;
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}
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// key_ancestors is a mapping of page attribute keys to a stack of
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// Pages nodes that contain values for them.
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std::map<std::string, std::vector<QPDFObjectHandle> > key_ancestors;
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this->all_pages.clear();
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pushInheritedAttributesToPageInternal(
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this->trailer.getKey("/Root").getKey("/Pages"),
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key_ancestors, this->all_pages, allow_changes, warn_skipped_keys);
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assert(key_ancestors.empty());
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this->pushed_inherited_attributes_to_pages = true;
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}
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void
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QPDF::pushInheritedAttributesToPageInternal(
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QPDFObjectHandle cur_pages,
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std::map<std::string, std::vector<QPDFObjectHandle> >& key_ancestors,
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std::vector<QPDFObjectHandle>& pages,
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bool allow_changes, bool warn_skipped_keys)
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{
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std::set<QPDFObjGen> visited;
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pushInheritedAttributesToPageInternal2(
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cur_pages, key_ancestors, pages, allow_changes,
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warn_skipped_keys, visited);
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}
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void
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QPDF::pushInheritedAttributesToPageInternal2(
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QPDFObjectHandle cur_pages,
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std::map<std::string, std::vector<QPDFObjectHandle> >& key_ancestors,
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std::vector<QPDFObjectHandle>& pages,
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bool allow_changes, bool warn_skipped_keys,
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std::set<QPDFObjGen>& visited)
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{
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QPDFObjGen this_og = cur_pages.getObjGen();
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if (visited.count(this_og) > 0)
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{
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throw QPDFExc(
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qpdf_e_pages, this->file->getName(),
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this->last_object_description, 0,
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"Loop detected in /Pages structure (inherited attributes)");
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}
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visited.insert(this_og);
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// Extract the underlying dictionary object
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std::string type = cur_pages.getKey("/Type").getName();
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if (type == "/Pages")
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{
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// Make a list of inheritable keys. Any key other than /Type,
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// /Parent, Kids, or /Count is an inheritable attribute. Push
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// this object onto the stack of pages nodes that have values
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// for this attribute.
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std::set<std::string> inheritable_keys;
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std::set<std::string> keys = cur_pages.getKeys();
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for (std::set<std::string>::iterator iter = keys.begin();
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iter != keys.end(); ++iter)
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{
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std::string const& key = *iter;
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if ( (key == "/MediaBox") || (key == "/CropBox") ||
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(key == "/Resources") || (key == "/Rotate") )
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{
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if (! allow_changes)
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{
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throw QPDFExc(qpdf_e_internal, this->file->getName(),
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this->last_object_description,
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this->file->getLastOffset(),
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"optimize detected an "
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"inheritable attribute when called "
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"in no-change mode");
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}
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// This is an inheritable resource
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inheritable_keys.insert(key);
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QPDFObjectHandle oh = cur_pages.getKey(key);
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QTC::TC("qpdf", "QPDF opt direct pages resource",
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oh.isIndirect() ? 0 : 1);
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if (! oh.isIndirect())
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{
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if (! oh.isScalar())
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{
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// Replace shared direct object non-scalar
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// resources with indirect objects to avoid
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// copying large structures around.
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cur_pages.replaceKey(key, makeIndirectObject(oh));
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oh = cur_pages.getKey(key);
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}
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else
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{
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// It's okay to copy scalars.
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QTC::TC("qpdf", "QPDF opt inherited scalar");
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}
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}
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key_ancestors[key].push_back(oh);
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if (key_ancestors[key].size() > 1)
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{
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QTC::TC("qpdf", "QPDF opt key ancestors depth > 1");
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}
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// Remove this resource from this node. It will be
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// reattached at the page level.
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cur_pages.removeKey(key);
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}
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else if (! ((key == "/Type") || (key == "/Parent") ||
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(key == "/Kids") || (key == "/Count")))
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{
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// Warn when flattening, but not if the key is at the top
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// level (i.e. "/Parent" not set), as we don't change these;
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// but flattening removes intermediate /Pages nodes.
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if ( (warn_skipped_keys) && (cur_pages.hasKey("/Parent")) )
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{
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QTC::TC("qpdf", "QPDF unknown key not inherited");
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setLastObjectDescription("Pages object",
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cur_pages.getObjectID(),
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cur_pages.getGeneration());
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warn(QPDFExc(qpdf_e_pages, this->file->getName(),
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this->last_object_description, 0,
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"Unknown key " + key + " in /Pages object"
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" is being discarded as a result of"
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" flattening the /Pages tree"));
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}
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}
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}
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// Visit descendant nodes.
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QPDFObjectHandle kids = cur_pages.getKey("/Kids");
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int n = kids.getArrayNItems();
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for (int i = 0; i < n; ++i)
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{
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pushInheritedAttributesToPageInternal2(
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kids.getArrayItem(i), key_ancestors, pages,
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allow_changes, warn_skipped_keys, visited);
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}
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// For each inheritable key, pop the stack. If the stack
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// becomes empty, remove it from the map. That way, the
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// invariant that the list of keys in key_ancestors is exactly
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// those keys for which inheritable attributes are available.
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if (! inheritable_keys.empty())
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{
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QTC::TC("qpdf", "QPDF opt inheritable keys");
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for (std::set<std::string>::iterator iter =
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inheritable_keys.begin();
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iter != inheritable_keys.end(); ++iter)
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{
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std::string const& key = (*iter);
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key_ancestors[key].pop_back();
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if (key_ancestors[key].empty())
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{
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QTC::TC("qpdf", "QPDF opt erase empty key ancestor");
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key_ancestors.erase(key);
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}
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}
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}
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else
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{
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QTC::TC("qpdf", "QPDF opt no inheritable keys");
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}
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}
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else if (type == "/Page")
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{
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// Add all available inheritable attributes not present in
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// this object to this object.
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for (std::map<std::string, std::vector<QPDFObjectHandle> >::iterator
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iter = key_ancestors.begin();
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iter != key_ancestors.end(); ++iter)
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{
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std::string const& key = (*iter).first;
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if (! cur_pages.hasKey(key))
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{
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QTC::TC("qpdf", "QPDF opt resource inherited");
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cur_pages.replaceKey(key, (*iter).second.back());
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}
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else
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{
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QTC::TC("qpdf", "QPDF opt page resource hides ancestor");
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}
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}
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pages.push_back(cur_pages);
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}
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else
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{
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throw QPDFExc(qpdf_e_damaged_pdf, this->file->getName(),
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this->last_object_description,
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this->file->getLastOffset(),
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"invalid Type " + type + " in page tree");
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}
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visited.erase(this_og);
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}
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void
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QPDF::updateObjectMaps(ObjUser const& ou, QPDFObjectHandle oh)
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{
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std::set<QPDFObjGen> visited;
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updateObjectMapsInternal(ou, oh, visited, true);
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}
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void
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QPDF::updateObjectMapsInternal(ObjUser const& ou, QPDFObjectHandle oh,
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std::set<QPDFObjGen>& visited, bool top)
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{
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// Traverse the object tree from this point taking care to avoid
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// crossing page boundaries.
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bool is_page_node = false;
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if (oh.isDictionary() && oh.hasKey("/Type"))
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{
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std::string type = oh.getKey("/Type").getName();
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if (type == "/Page")
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{
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is_page_node = true;
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if (! top)
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{
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return;
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}
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}
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}
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if (oh.isIndirect())
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{
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QPDFObjGen og(oh.getObjGen());
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if (visited.count(og))
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{
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QTC::TC("qpdf", "QPDF opt loop detected");
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return;
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}
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this->obj_user_to_objects[ou].insert(og);
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this->object_to_obj_users[og].insert(ou);
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visited.insert(og);
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}
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if (oh.isArray())
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{
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int n = oh.getArrayNItems();
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for (int i = 0; i < n; ++i)
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{
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updateObjectMapsInternal(ou, oh.getArrayItem(i), visited, false);
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}
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}
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else if (oh.isDictionary() || oh.isStream())
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{
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QPDFObjectHandle dict = oh;
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if (oh.isStream())
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{
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dict = oh.getDict();
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}
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std::set<std::string> keys = dict.getKeys();
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for (std::set<std::string>::iterator iter = keys.begin();
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iter != keys.end(); ++iter)
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{
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std::string const& key = *iter;
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if (is_page_node && (key == "/Thumb"))
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{
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// Traverse page thumbnail dictionaries as a special
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// case.
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updateObjectMaps(ObjUser(ObjUser::ou_thumb, ou.pageno),
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dict.getKey(key));
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}
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else if (is_page_node && (key == "/Parent"))
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{
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// Don't traverse back up the page tree
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}
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else
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{
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updateObjectMapsInternal(ou, dict.getKey(key),
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visited, false);
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}
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}
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}
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}
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void
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QPDF::filterCompressedObjects(std::map<int, int> const& object_stream_data)
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{
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if (object_stream_data.empty())
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{
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return;
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}
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// Transform object_to_obj_users and obj_user_to_objects so that
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// they refer only to uncompressed objects. If something is a
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// user of a compressed object, then it is really a user of the
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// object stream that contains it.
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std::map<ObjUser, std::set<QPDFObjGen> > t_obj_user_to_objects;
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std::map<QPDFObjGen, std::set<ObjUser> > t_object_to_obj_users;
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for (std::map<ObjUser, std::set<QPDFObjGen> >::iterator i1 =
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this->obj_user_to_objects.begin();
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i1 != this->obj_user_to_objects.end(); ++i1)
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{
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ObjUser const& ou = (*i1).first;
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std::set<QPDFObjGen> const& objects = (*i1).second;
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for (std::set<QPDFObjGen>::const_iterator i2 = objects.begin();
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i2 != objects.end(); ++i2)
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{
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QPDFObjGen const& og = (*i2);
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std::map<int, int>::const_iterator i3 =
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object_stream_data.find(og.getObj());
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if (i3 == object_stream_data.end())
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{
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t_obj_user_to_objects[ou].insert(og);
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}
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else
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{
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t_obj_user_to_objects[ou].insert(QPDFObjGen((*i3).second, 0));
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}
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}
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}
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for (std::map<QPDFObjGen, std::set<ObjUser> >::iterator i1 =
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this->object_to_obj_users.begin();
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i1 != this->object_to_obj_users.end(); ++i1)
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{
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QPDFObjGen const& og = (*i1).first;
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std::set<ObjUser> const& objusers = (*i1).second;
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for (std::set<ObjUser>::const_iterator i2 = objusers.begin();
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i2 != objusers.end(); ++i2)
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{
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ObjUser const& ou = (*i2);
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std::map<int, int>::const_iterator i3 =
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object_stream_data.find(og.getObj());
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if (i3 == object_stream_data.end())
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{
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t_object_to_obj_users[og].insert(ou);
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}
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else
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{
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t_object_to_obj_users[QPDFObjGen((*i3).second, 0)].insert(ou);
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}
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}
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}
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this->obj_user_to_objects = t_obj_user_to_objects;
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this->object_to_obj_users = t_object_to_obj_users;
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}
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