Support output_io in Compressable

lib/fluent/plugin/compressable.rb

@@ -19,32 +19,50 @@
 module Fluent
   module Plugin
     module Compressable
-      def compress(data)
-        io = StringIO.new
+      def compress(data, **kwargs)
+        output_io = kwargs[:output_io]
+        io = output_io || StringIO.new
         Zlib::GzipWriter.wrap(io) do |gz|
           gz.write data
         end
-        io.string
+
+        output_io || io.string
       end
 
       # compressed_data is String like `compress(data1) + compress(data2) + ... + compress(dataN)`
       # https://www.ruby-forum.com/topic/971591#979503
-      def decompress(compressed_data, **kargs)
-        io = kargs[:io] || StringIO.new(compressed_data)
-        ret = ''
-
-        loop do
-          gz = Zlib::GzipReader.new(io)
-          ret += gz.read
-          unused = gz.unused
-          gz.finish
-
-          break if unused.nil?
-          adjust = unused.length
-          io.pos -= adjust
-        end
+      def decompress(compressed_data, **kwargs)
+        return compressed_data if compressed_data.empty?
+        io = StringIO.new(compressed_data)
+
+        if kwargs[:output_io]
+          out = kwargs[:output_io]
+          loop do
+            gz = Zlib::GzipReader.new(io)
+            out.write(gz.read)
+            unused = gz.unused
+            gz.finish
 
-        ret
+            break if unused.nil?
+            adjust = unused.length
+            io.pos -= adjust
+          end
+          out
+        else
+          out = ''
+          loop do
+            gz = Zlib::GzipReader.new(io)
+            out += gz.read
+            unused = gz.unused
+            gz.finish
+
+            break if unused.nil?
+            adjust = unused.length
+            io.pos -= adjust
+          end
+
+          out
+        end
       end
     end
   end

test/plugin/test_compressable.rb

@@ -10,6 +10,14 @@ class CompressableTest < Test::Unit::TestCase
       compressed_str = compress(str)
       assert_not_equal compressed_str, str
     end
+
+    test 'write compressed data to IO with output_io option' do
+      str = 'text data'
+      compressed_str = compress(str)
+      io = StringIO.new
+      compress(str, output_io: io)
+      assert_equal compressed_str, io.string
+    end
   end
 
   sub_test_case '#decompress' do
@@ -19,10 +27,12 @@ class CompressableTest < Test::Unit::TestCase
       assert_equal str, decompress(compressed_str)
     end
 
-    test 'decompress compressed data with io option' do
+    test 'write decompressed data to IO with output_io option' do
       str = 'text data'
       compressed_str = compress(str)
-      assert_equal str, decompress('', io: StringIO.new(compressed_str))
+      io = StringIO.new
+      decompress(compressed_str, output_io: io)
+      assert_equal str, io.string
     end
 
     test 'decompress multiple compressed data' do