Remove unreferenced: ignore names that are not Fonts or XObjects

Converted ResourceFinder to ParserCallbacks so we can better detect
the name that precedes various operators and use the operators to sort
the names into resource types. This enables us to be smarter about
detecting unreferenced resources in pages and also sets the stage for
reconciling differences in /DR across documents.

1 files changed, 43 insertions, 12 deletions

diff --git a/libqpdf/ResourceFinder.cc b/libqpdf/ResourceFinder.cc
index 74ba671f..6b9929e4 100644
--- a/libqpdf/ResourceFinder.cc
+++ b/libqpdf/ResourceFinder.cc
@@ -1,28 +1,53 @@
 #include <qpdf/ResourceFinder.hh>
 
 ResourceFinder::ResourceFinder() :
+    last_name_offset(0),
     saw_bad(false)
 {
 }
 
 void
-ResourceFinder::handleToken(QPDFTokenizer::Token const& token)
+ResourceFinder::handleObject(QPDFObjectHandle obj, size_t offset, size_t)
 {
-    if ((token.getType() == QPDFTokenizer::tt_word) &&
-        (! this->last_name.empty()))
+    if (obj.isOperator() && (! this->last_name.empty()))
     {
-        this->names.insert(this->last_name);
+        static std::map<std::string, std::string> op_to_rtype = {
+            {"CS", "/ColorSpace"},
+            {"cs", "/ColorSpace"},
+            {"gs", "/ExtGState"},
+            {"Tf", "/Font"},
+            {"SCN", "/Pattern"},
+            {"scn", "/Pattern"},
+            {"BDC", "/Properties"},
+            {"DP", "/Properties"},
+            {"sh", "/Shading"},
+            {"Do", "/XObject"},
+        };
+        std::string op = obj.getOperatorValue();
+        std::string resource_type;
+        auto iter = op_to_rtype.find(op);
+        if (iter != op_to_rtype.end())
+        {
+            resource_type = iter->second;
+        }
+        if (! resource_type.empty())
+        {
+            this->names.insert(this->last_name);
+            this->names_by_resource_type[
+                resource_type][this->last_name].insert(this->last_name_offset);
+        }
     }
-    else if (token.getType() == QPDFTokenizer::tt_name)
+    else if (obj.isName())
     {
-        this->last_name =
-            QPDFObjectHandle::newName(token.getValue()).getName();
+        this->last_name = obj.getName();
+        this->last_name_offset = offset;
     }
-    else if (token.getType() == QPDFTokenizer::tt_bad)
-    {
-        saw_bad = true;
-    }
-    writeToken(token);
+}
+
+void
+ResourceFinder::handleWarning()
+{
+    this->saw_bad = true;
 }
 
 std::set<std::string> const&
@@ -31,6 +56,12 @@ ResourceFinder::getNames() const
     return this->names;
 }
 
+std::map<std::string, std::map<std::string, std::set<size_t>>> const&
+ResourceFinder::getNamesByResourceType() const
+{
+    return this->names_by_resource_type;
+}
+
 bool
 ResourceFinder::sawBad() const
 {