--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/go/gofrontend/go-sha1.h	Fri Oct 27 22:46:09 2017 +0900
@@ -0,0 +1,33 @@
+// go-sha1.h -- GCC specific sha1 checksum utilities.   -*- C++ -*-
+
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#ifndef GO_SHA1_H
+#define GO_SHA1_H
+
+#include "go-system.h"
+
+//
+// Interface class for computation of SHA1 checksums. Front end requests
+// one of these objects from the back end to use for computing
+// checksums (each back end tends to have a different SHA1 implementation).
+// Back ends are expected to create a new class that derives from this
+// one containing an implementation.
+//
+
+class Go_sha1_helper
+{
+ public:
+  virtual ~Go_sha1_helper() { }
+  virtual void process_bytes(const void* buffer, size_t len) = 0;
+  virtual std::string finish() = 0;
+  static const int checksum_len = 20;
+};
+
+// Call to create and return a new sha1 helper (this routine defined
+// by the backend). Caller is responsible for deletion.
+extern Go_sha1_helper* go_create_sha1_helper();
+
+#endif // !defined(GO_SHA1_H)