Refactor filter name expansion logic into a dedicated method

Moved the filter abbreviation expansion logic from a static map to a new `expand_filter_name` method in `QPDF_Stream::Members`. This simplifies the code, improves maintainability, and consolidates the logic for easier testing and updates.

Refactor filter name expansion logic into a dedicated method
Moved the filter abbreviation expansion logic from a static map to a new `expand_filter_name` method in `QPDF_Stream::Members`. This simplifies the code, improves maintainability, and consolidates the logic for easier testing and updates.
m-holger
1 parent e9359c72
Showing 3 changed files with 27 additions and 13 deletions
libqpdf/QPDF_Stream.cc
libqpdf/qpdf/QPDFObject_private.hh
qpdf/qpdf.testcov
@@ -80,17 +80,34 @@ namespace
     };
 } // namespace
-std::map<std::string, std::string> Stream::filter_abbreviations = {
+std::string
+QPDF_Stream::Members::expand_filter_name(std::string const& name) const
+{
     // The PDF specification provides these filter abbreviations for use in inline images, but
     // according to table H.1 in the pre-ISO versions of the PDF specification, Adobe Reader also
     // accepts them for stream filters.
-    {"/AHx", "/ASCIIHexDecode"},
-    {"/A85", "/ASCII85Decode"},
-    {"/LZW", "/LZWDecode"},
-    {"/Fl", "/FlateDecode"},
-    {"/RL", "/RunLengthDecode"},
-    {"/CCF", "/CCITTFaxDecode"},
-    {"/DCT", "/DCTDecode"},
+    if (name == "/AHx") {
+        return "/ASCIIHexDecode";
+    }
+    if (name == "/A85") {
+        return "/ASCII85Decode";
+    }
+    if (name == "/LZW") {
+        return "/LZWDecode";
+    }
+    if (name == "/Fl") {
+        return "/FlateDecode";
+    }
+    if (name == "/RL") {
+        return "/RunLengthDecode";
+    }
+    if (name == "/CCF") {
+        return "/CCITTFaxDecode";
+    }
+    if (name == "/DCT") {
+        return "/DCTDecode";
+    }
+    return name;
 };
 std::map<std::string, std::function<std::shared_ptr<QPDFStreamFilter>()>> Stream::filter_factories =
@@ -333,10 +350,7 @@ Stream::filterable(
     bool filterable = true;
     for (auto& filter_name: filter_names) {
-        if (filter_abbreviations.count(filter_name)) {
-            QTC::TC("qpdf", "QPDF_Stream expand filter abbreviation");
-            filter_name = filter_abbreviations[filter_name];
-        }
+        filter_name = s->expand_filter_name(filter_name);
         auto ff = filter_factories.find(filter_name);
         if (ff == filter_factories.end()) {
@@ -226,6 +226,7 @@ class QPDF_Stream final
         std::shared_ptr<Buffer> stream_data;
         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;
     };
     friend class QPDFObject;
@@ -177,7 +177,6 @@ QPDFObjectHandle prepend page contents 0
 QPDFObjectHandle append page contents 0
 QPDF_Stream getRawStreamData 0
 QPDF_Stream getStreamData 0
-QPDF_Stream expand filter abbreviation 0
 qpdf-c called qpdf_read_memory 0
 QPDF stream without newline 0
 QPDF stream with CR only 0