Refactor stream filter handling for improved modularity

Moved stream filter factory logic into `Members::filter_factory` for better encapsulation and maintainability. Removed redundant static filter factory map and improved error handling for invalid stream filter configurations.

Refactor stream filter handling for improved modularity
Moved stream filter factory logic into `Members::filter_factory` for better encapsulation and maintainability. Removed redundant static filter factory map and improved error handling for invalid stream filter configurations.
m-holger
1 parent ab806259
Showing 4 changed files with 60 additions and 36 deletions
libqpdf/QPDF_Stream.cc
libqpdf/qpdf/QPDFObjectHandle_private.hh
libqpdf/qpdf/QPDFObject_private.hh
qpdf/qpdf.testcov
@@ -78,6 +78,9 @@ namespace
         Stream stream;
         qpdf_stream_decode_level_e decode_level;
     };
+
+    /// User defined streamfilter factories
+    std::map<std::string, std::function<std::shared_ptr<QPDFStreamFilter>()>> filter_factories;
 } // namespace
  
 std::string
@@ -110,16 +113,47 @@ QPDF_Stream::Members::expand_filter_name(std::string const&amp; name) const
     return name;
 };
  
-std::map<std::string, std::function<std::shared_ptr<QPDFStreamFilter>()>> Stream::filter_factories =
-    {
-        {"/Crypt", []() { return std::make_shared<SF_Crypt>(); }},
-        {"/FlateDecode", SF_FlateLzwDecode::flate_factory},
-        {"/LZWDecode", SF_FlateLzwDecode::lzw_factory},
-        {"/RunLengthDecode", SF_RunLengthDecode::factory},
-        {"/DCTDecode", SF_DCTDecode::factory},
-        {"/ASCII85Decode", SF_ASCII85Decode::factory},
-        {"/ASCIIHexDecode", SF_ASCIIHexDecode::factory},
-};
+std::function<std::shared_ptr<QPDFStreamFilter>()>
+QPDF_Stream::Members::filter_factory(std::string const& name) const
+{
+    auto e_name = expand_filter_name(name);
+    if (e_name == "/Crypt") {
+        return []() { return std::make_shared<SF_Crypt>(); };
+    }
+    if (e_name == "/FlateDecode") {
+        return SF_FlateLzwDecode::flate_factory;
+    }
+    if (e_name == "/LZWDecode") {
+        return SF_FlateLzwDecode::lzw_factory;
+    }
+    if (e_name == "/RunLengthDecode") {
+        return SF_RunLengthDecode::factory;
+    }
+    if (e_name == "/DCTDecode") {
+        return SF_DCTDecode::factory;
+    }
+    if (e_name == "/ASCII85Decode") {
+        return SF_ASCII85Decode::factory;
+    }
+    if (e_name == "/RunLengthDecode") {
+        return SF_RunLengthDecode::factory;
+    }
+    if (e_name == "/DCTDecode") {
+        return SF_DCTDecode::factory;
+    }
+    if (e_name == "/ASCII85Decode") {
+        return SF_ASCII85Decode::factory;
+    }
+    if (e_name == "/ASCIIHexDecode") {
+        return SF_ASCIIHexDecode::factory;
+    }
+
+    auto ff = filter_factories.find(e_name);
+    if (ff == filter_factories.end()) {
+        return nullptr;
+    }
+    return ff->second;
+}
  
 Stream::Stream(
     QPDF& qpdf, QPDFObjGen og, QPDFObjectHandle stream_dict, qpdf_offset_t offset, size_t length) :
@@ -316,52 +350,43 @@ Stream::filterable(
     auto s = stream();
     // Check filters
  
-    QPDFObjectHandle filter_obj = s->stream_dict.getKey("/Filter");
-    bool filters_okay = true;
+    auto filter_obj = s->stream_dict.getKey("/Filter");
  
     std::vector<std::string> filter_names;
  
     if (filter_obj.isNull()) {
         // No filters
-    } else if (filter_obj.isName()) {
+        return true;
+    }
+    if (filter_obj.isName()) {
         // One filter
-        filter_names.emplace_back(s->expand_filter_name(filter_obj.getName()));
+        filter_names.emplace_back(filter_obj.getName());
     } else if (filter_obj.isArray()) {
         // Potentially multiple filters
         int n = filter_obj.getArrayNItems();
         for (int i = 0; i < n; ++i) {
             QPDFObjectHandle item = filter_obj.getArrayItem(i);
-            if (item.isName()) {
-                filter_names.emplace_back(s->expand_filter_name(filter_obj.getName()));
-            } else {
-                filters_okay = false;
+            if (!item.isName()) {
+                warn("stream filter type is not name or array");
+                return false;
             }
+            filter_names.emplace_back(item.getName());
         }
     } else {
-        filters_okay = false;
-    }
-
-    if (!filters_okay) {
-        QTC::TC("qpdf", "QPDF_Stream invalid filter");
         warn("stream filter type is not name or array");
         return false;
     }
  
-    bool filterable = true;
-
     for (auto& filter_name: filter_names) {
-        auto ff = filter_factories.find(filter_name);
-        if (ff == filter_factories.end()) {
-            filterable = false;
-        } else {
-            filters.push_back((ff->second)());
+        if (auto ff = s->filter_factory(filter_name)) {
+            filters.emplace_back(ff());
+            continue;
         }
-    }
-
-    if (!filterable) {
         return false;
     }
  
+    bool filterable = true;
+
     // filters now contains a list of filters to be applied in order. See which ones we can support.
  
     // See if we can support any decode parameters that are specified.
@@ -321,8 +321,6 @@ namespace qpdf
         void warn(std::string const& message);
  
         static std::map<std::string, std::string> filter_abbreviations;
-        static std::map<std::string, std::function<std::shared_ptr<QPDFStreamFilter>()>>
-            filter_factories;
     };
  
     template <typename T>
@@ -227,6 +227,8 @@ class QPDF_Stream final
         std::shared_ptr<QPDFObjectHandle::StreamDataProvider> stream_provider;
         std::vector<std::shared_ptr<QPDFObjectHandle::TokenFilter>> token_filters;
         std::string expand_filter_name(std::string const& name) const;
+        std::function<std::shared_ptr<QPDFStreamFilter>()>
+        filter_factory(std::string const& name) const;
     };
  
     friend class QPDFObject;
@@ -77,7 +77,6 @@ QPDFTokenizer bad hexstring 2nd character 0
 QPDFTokenizer null in name 0
 QPDFTokenizer bad name 1 0
 QPDFTokenizer bad name 2 0
-QPDF_Stream invalid filter 0
 QPDF UseOutlines but no Outlines 0
 QPDFObjectHandle makeDirect loop 0
 QPDFObjectHandle copy stream 1