Improve magic_match_io to also use seek for regexp

lib/marcel/magic.rb

@@ -123,34 +123,33 @@ def self.magic_match(io, method)
 
     def self.magic_match_io(io, matches, buffer)
       matches.any? do |offset, value, children|
-        match =
-          if value
-            if value.is_a?(Regexp)
-              match_regex(io, offset, value, buffer)
-            elsif Range === offset
-              io_seek(io, offset.begin, buffer)
-              x = io.read(offset.end - offset.begin + value.bytesize, buffer)
-              x && x.include?(value)
-            else
-              io_seek(io, offset, buffer)
-              io.read(value.bytesize, buffer) == value
-            end
+        match = if value
+          is_range = Range === offset
+          is_regexp = Regexp === value
+          sample_size = is_regexp ? 256 : value.bytesize
+
+          x = if is_range
+            io_seek(io, offset.begin, buffer)
+            io.read(offset.end - offset.begin + sample_size, buffer)
+          else
+            io_seek(io, offset, buffer)
+            io.read(sample_size, buffer)
           end
 
+          if is_regexp
+            x&.match?(value)
+          elsif is_range
+            x&.include?(value)
+          else
+            x == value
+          end
+        end
+
         io.rewind
         match && (!children || magic_match_io(io, children, buffer))
       end
     end
 
-    def self.match_regex(io, offset, regexp, buffer)
-      start = offset.is_a?(Range) ? offset.begin : offset
-      io.read(start, buffer) if start > 0
-      data = io.read(256, buffer)
-      return false unless data
-
-      data.match?(regexp)
-    end
-
     def self.io_seek(io, offset, buffer)
       return if offset == 0
 
@@ -162,6 +161,6 @@ def self.io_seek(io, offset, buffer)
       end
     end
 
-    private_class_method :magic_match, :magic_match_io, :match_regex, :io_seek
+    private_class_method :magic_match, :magic_match_io, :io_seek
   end
 end

test/magic_test.rb

@@ -50,30 +50,25 @@ class Marcel::MimeType::MagicTest < Marcel::TestCase
 
   test "none of the regex patterns should match random test data" do
     ignore_list = %w( application/x-dbf )
-    
+
     extract_regexes = lambda do |matching_rules, collected = []|
       matching_rules.each do |offset, value, children|
         collected << [offset, value] if value.is_a?(Regexp)
         extract_regexes.call(children, collected) if children
       end
       collected
     end
-    
+
     # Use a test string that's very unlikely to match any file format regex
     # Using only high Unicode characters and very specific patterns
     test_data = "🇨🇭 \xFF\xFE\x03\x05\x06🧀 cheese\x06\x07\x03"
-    
+
     Marcel::MAGIC.each do |type, matching_rules|
       next if ignore_list.include?(type)
       regexes = extract_regexes.call(matching_rules)
-
-      regexes.each do |offset, regex|
-        buffer = (+"").encode(Encoding::BINARY)
-
-        result = Marcel::Magic.send(:match_regex, StringIO.new(test_data), offset, regex, buffer)
-
-        assert_equal false, result, "Test data unexpectedly matched a file format regexp (#{type}, #{regex.inspect})"
-      end
+
+      result = Marcel::Magic.send(:magic_match_io, StringIO.new(test_data), regexes, "".b)
+      assert_equal false, result, "Test data unexpectedly matched a file format regexp (#{type}, #{regexes.inspect})"
     end
   end