Fix Zlib::Deflate#params after breaking out of #deflate

ext/zlib/zlib.c

@@ -1216,6 +1216,8 @@ zstream_run_try(VALUE value_arg)
 		}
 	    }
 	}
+	z->stream.next_in = Z_NULL;
+	z->stream.avail_in = 0;
 	raise_zlib_error(err, z->stream.msg);
     }
 
@@ -1225,6 +1227,9 @@ zstream_run_try(VALUE value_arg)
     if (!NIL_P(old_input)) {
 	rb_str_resize(old_input, 0);
     }
+    /* the rest is in z->input now; do not leave next_in in old_input */
+    z->stream.next_in = Z_NULL;
+    z->stream.avail_in = 0;
 
     return Qnil;
 }
@@ -2144,7 +2149,8 @@ do_inflate(struct zstream *z, VALUE src)
 	return;
     }
     StringValue(src);
-    if (RSTRING_LEN(src) > 0 || z->stream.avail_in > 0) { /* prevent Z_BUF_ERROR */
+    if (RSTRING_LEN(src) > 0 ||
+	(!NIL_P(z->input) && RSTRING_LEN(z->input) > 0)) { /* prevent Z_BUF_ERROR */
 	zstream_run(z, (Bytef*)RSTRING_PTR(src), RSTRING_LEN(src), Z_SYNC_FLUSH);
     }
 }

test/zlib/test_zlib.rb

@@ -102,6 +102,38 @@ def test_deflate_chunked_break
       assert_equal input, original
     end
 
+    def test_params_after_chunked_break
+      chunks = []
+      r = Random.new 0
+
+      # small enough that params can flush what zlib holds without Z_BUF_ERROR
+      z = Zlib::Deflate.new(Zlib::DEFAULT_COMPRESSION, 9, 1)
+
+      input = r.bytes(20000)
+      z.deflate(input) do |chunk|
+        chunks << chunk
+        break
+      end
+
+      assert_operator 0, :<, z.avail_in
+
+      z.params(Zlib::BEST_SPEED, Zlib::FILTERED)
+      chunks << z.finish
+
+      assert_equal input, Zlib.inflate(chunks.join)
+    end
+
+    def test_params_after_failed_deflate
+      z = Zlib::Deflate.new
+      z << "foo"
+      assert_raise(Zlib::StreamError) { z.deflate("bar", 10000) }
+      assert_equal "bar", z.flush_next_in
+
+      z.params(Zlib::BEST_SPEED, Zlib::FILTERED)
+
+      assert_equal "foo", Zlib::Inflate.inflate(z.finish)
+    end
+
     def test_addstr
       z = Zlib::Deflate.new
       z << "foo"
@@ -620,6 +652,24 @@ def test_inflate_dictionary
       assert_equal "foofoofoo", out
     end
 
+    def test_inflate_empty_after_chunked_break
+      chunks = []
+      input = Random.new(0).bytes(20000)
+
+      z = Zlib::Inflate.new
+
+      z.inflate(Zlib.deflate(input)) do |chunk|
+        chunks << chunk
+        break
+      end
+
+      assert_operator 0, :<, z.avail_in
+
+      chunks << z.inflate("")
+
+      assert_equal input, chunks.join
+    end
+
     def test_sync
       z = Zlib::Deflate.new
       s = z.deflate("foo" * 1000, Zlib::FULL_FLUSH)