compiler: add abstraction layer for sha1 checksums.

Add new interface for the front end code to use when computing SHA1
    checksums; the intent is to allow the different implementation in
    different back ends.
    
    No change in functionality for gccgo; this is an enabling change to
    permit the front end to be used with other back ends (e.g. LLVM).
    
    Reviewed-on: https://go-review.googlesource.com/28833

	* go-sha1.cc: New file.
	* Make-lang.in (GO_OBJS): Add go/go-sha1.o.
	(CFLAGS-go/go-sha1.o): New variable.

From-SVN: r240053

gcc/go/ChangeLog

@@ -1,3 +1,9 @@
+2016-09-09  Than McIntosh  <thanm@google.com>
+
+	* go-sha1.cc: New file.
+	* Make-lang.in (GO_OBJS): Add go/go-sha1.o.
+	(CFLAGS-go/go-sha1.o): New variable.
+
 2016-09-01  Martin Sebor  <msebor@redhat.com>
 
 	* gofrontend/expressions.cc: Increase buffer size to guarantee

gcc/go/Make-lang.in

@@ -59,6 +59,7 @@ GO_OBJS = \
 	go/go-lang.o \
 	go/go-linemap.o \
 	go/go-optimize.o \
+	go/go-sha1.o \
 	go/go.o \
 	go/gogo.o \
 	go/import.o \
@@ -225,6 +226,7 @@ GOINCLUDES = -I $(srcdir)/go -I $(srcdir)/go/gofrontend
 
 CFLAGS-go/go-gcc.o += $(GOINCLUDES)
 CFLAGS-go/go-linemap.o += $(GOINCLUDES)
+CFLAGS-go/go-sha1.o += $(GOINCLUDES)
 
 go/%.o: go/gofrontend/%.cc
 	$(COMPILE) $(GOINCLUDES) $<

gcc/go/go-sha1.cc

@@ -0,0 +1,71 @@
+/* go-sha1.cc -- Go frontend interface to gcc backend.
+   Copyright (C) 2016 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "go-sha1.h"
+#include "sha1.h"
+
+class Gcc_sha1_helper : public Go_sha1_helper
+{
+ public:
+
+  Gcc_sha1_helper() : ctx_(new sha1_ctx) { sha1_init_ctx(this->ctx_); }
+
+  ~Gcc_sha1_helper();
+
+  // Incorporate 'len' bytes from 'buffer' into checksum.
+  void
+  process_bytes(const void* buffer, size_t len);
+
+  // Finalize checksum and return in the form of a string.
+  std::string
+  finish();
+
+ private:
+  sha1_ctx *ctx_;
+};
+
+Gcc_sha1_helper::~Gcc_sha1_helper()
+{
+  delete ctx_;
+}
+
+void
+Gcc_sha1_helper::process_bytes(const void* buffer, size_t len)
+{
+  sha1_process_bytes(buffer, len, this->ctx_);
+}
+
+std::string
+Gcc_sha1_helper::finish()
+{
+  // Use a union to provide the required alignment.
+  union
+  {
+    char checksum[checksum_len];
+    long align;
+  } u;
+  sha1_finish_ctx(this->ctx_, u.checksum);
+  return std::string(u.checksum, checksum_len);
+}
+
+Go_sha1_helper*
+go_create_sha1_helper()
+{
+  return new Gcc_sha1_helper();
+}

gcc/go/gofrontend/MERGE

@@ -1,4 +1,4 @@
-4de301275dfed034a1dd9dff3d1af8643ee5cb4b
+2022ddc85f812b6990b72c7e95b8207e07ac8984
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.

gcc/go/gofrontend/export.cc

@@ -6,8 +6,7 @@
 
 #include "go-system.h"
 
-#include "sha1.h"
-
+#include "go-sha1.h"
 #include "go-c.h"
 
 #include "gogo.h"
@@ -40,6 +39,7 @@ const int Export::checksum_len;
 Export::Export(Stream* stream)
   : stream_(stream), type_refs_(), type_index_(1), packages_()
 {
+  go_assert(Export::checksum_len == Go_sha1_helper::checksum_len);
 }
 
 // A functor to sort Named_object pointers by name.
@@ -686,9 +686,8 @@ Export::register_builtin_type(Gogo* gogo, const char* name, Builtin_code code)
 
 Export::Stream::Stream()
 {
-  this->checksum_ = new sha1_ctx;
-  memset(this->checksum_, 0, sizeof(sha1_ctx));
-  sha1_init_ctx(this->checksum_);
+  this->sha1_helper_ = go_create_sha1_helper();
+  go_assert(this->sha1_helper_ != NULL);
 }
 
 Export::Stream::~Stream()
@@ -701,7 +700,7 @@ Export::Stream::~Stream()
 void
 Export::Stream::write_and_sum_bytes(const char* bytes, size_t length)
 {
-  sha1_process_bytes(bytes, length, this->checksum_);
+  this->sha1_helper_->process_bytes(bytes, length);
   this->do_write(bytes, length);
 }
 
@@ -710,14 +709,9 @@ Export::Stream::write_and_sum_bytes(const char* bytes, size_t length)
 std::string
 Export::Stream::checksum()
 {
-  // Use a union to provide the required alignment.
-  union
-  {
-    char checksum[Export::checksum_len];
-    long align;
-  } u;
-  sha1_finish_ctx(this->checksum_, u.checksum);
-  return std::string(u.checksum, Export::checksum_len);
+  std::string rval = this->sha1_helper_->finish();
+  delete this->sha1_helper_;
+  return rval;
 }
 
 // Write the checksum string to the export data.

gcc/go/gofrontend/export.h

@@ -9,7 +9,7 @@
 
 #include "string-dump.h"
 
-struct sha1_ctx;
+class Go_sha1_helper;
 class Gogo;
 class Import_init;
 class Bindings;
@@ -109,8 +109,8 @@ class Export : public String_dump
     void
     write_and_sum_bytes(const char*, size_t);
 
-    // The checksum.
-    sha1_ctx* checksum_;
+    // The checksum helper.
+    Go_sha1_helper* sha1_helper_;
   };
 
   Export(Stream*);

gcc/go/gofrontend/go-sha1.h

@@ -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)