Refactor removal of unreferenced resources

Refactor in preparation for resolving unresolved resources in form xobjects from page.

Refactor removal of unreferenced resources
Refactor in preparation for resolving unresolved resources in form xobjects from page.
Jay Berkenbilt
1 parent 5fdf37b1
Showing 2 changed files with 31 additions and 33 deletions
include/qpdf/QPDFPageObjectHelper.hh
libqpdf/QPDFPageObjectHelper.cc
@@ -319,7 +319,7 @@ class QPDFPageObjectHelper: public QPDFObjectHelper
   private:
     static void
     removeUnreferencedResourcesHelper(
-        QPDFPageObjectHelper ph, std::set<QPDFObjGen>& seen);
+        QPDFPageObjectHelper ph);
     class Members
     {
@@ -703,13 +703,8 @@ NameWatcher::handleToken(QPDFTokenizer::Token const&amp; token)
 void
 QPDFPageObjectHelper::removeUnreferencedResourcesHelper(
-    QPDFPageObjectHelper ph, std::set<QPDFObjGen>& seen)
+    QPDFPageObjectHelper ph)
 {
-    if (seen.count(ph.oh.getObjGen()))
-    {
-        return;
-    }
-    seen.insert(ph.oh.getObjGen());
     NameWatcher nw;
     try
     {
@@ -730,39 +725,35 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper(
             "not attempting to remove unreferenced objects from this page");
         return;
     }
-    // Walk through /Font and /XObject dictionaries, removing any
-    // resources that are not referenced. We must make copies of
+
+    // We will walk through /Font and /XObject dictionaries, removing
+    // any resources that are not referenced. We must make copies of
     // resource dictionaries down into the dictionaries are mutating
     // to prevent mutating one dictionary from having the side effect
     // of mutating the one it was copied from.
-    std::vector<std::string> to_filter;
-    to_filter.push_back("/Font");
-    to_filter.push_back("/XObject");
     QPDFObjectHandle resources = ph.getAttribute("/Resources", true);
-    for (std::vector<std::string>::iterator d_iter = to_filter.begin();
-         d_iter != to_filter.end(); ++d_iter)
+    std::vector<QPDFObjectHandle> rdicts;
+    if (resources.isDictionary())
     {
-        QPDFObjectHandle dict = resources.getKey(*d_iter);
-        if (! dict.isDictionary())
-        {
-            continue;
-        }
-        dict = dict.shallowCopy();
-        resources.replaceKey(*d_iter, dict);
-        std::set<std::string> keys = dict.getKeys();
-        for (std::set<std::string>::iterator k_iter = keys.begin();
-             k_iter != keys.end(); ++k_iter)
+        std::vector<std::string> to_filter = {"/Font", "/XObject"};
+        for (auto const& iter: to_filter)
         {
-            if (! nw.names.count(*k_iter))
+            QPDFObjectHandle dict = resources.getKey(iter);
+            if (dict.isDictionary())
             {
-                dict.removeKey(*k_iter);
+                dict = dict.shallowCopy();
+                resources.replaceKey(iter, dict);
+                rdicts.push_back(dict);
             }
-            QPDFObjectHandle resource = dict.getKey(*k_iter);
-            if (resource.isFormXObject())
+        }
+    }
+    for (auto& dict: rdicts)
+    {
+        for (auto const& key: dict.getKeys())
+        {
+            if (! nw.names.count(key))
             {
-                QTC::TC("qpdf", "QPDFPageObjectHelper filter form xobject");
-                removeUnreferencedResourcesHelper(
-                    QPDFPageObjectHelper(resource), seen);
+                dict.removeKey(key);
             }
         }
     }
@@ -771,8 +762,15 @@ QPDFPageObjectHelper::removeUnreferencedResourcesHelper(
 void
 QPDFPageObjectHelper::removeUnreferencedResources()
 {
-    std::set<QPDFObjGen> seen;
-    removeUnreferencedResourcesHelper(*this, seen);
+    forEachFormXObject(
+        true,
+        [](
+            QPDFObjectHandle& obj, QPDFObjectHandle&, std::string const&)
+        {
+            QTC::TC("qpdf", "QPDFPageObjectHelper filter form xobject");
+            removeUnreferencedResourcesHelper(QPDFPageObjectHelper(obj));
+        });
+    removeUnreferencedResourcesHelper(*this);
 }
 QPDFPageObjectHelper