Support more configurability in GN toolchains

tools/gn/ninja_helper.h

-// Copyright (c) 2013 The Chromium 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 TOOLS_GN_NINJA_HELPER_H_
-#define TOOLS_GN_NINJA_HELPER_H_
-
-#include <iosfwd>
-#include <string>
-
-#include "tools/gn/filesystem_utils.h"
-#include "tools/gn/output_file.h"
-#include "tools/gn/target.h"
-
-class BuildSettings;
-class SourceDir;
-class SourceFile;
-class Target;
-
-// NinjaHelper -----------------------------------------------------------------
-
-class NinjaHelper {
- public:
-  NinjaHelper(const BuildSettings* build_settings);
-  ~NinjaHelper();
-
-  // Ends in a slash.
-  std::string GetTopleveOutputDir() const;
-
-  // Ends in a slash.
-  OutputFile GetTargetOutputDir(const Target* target) const;
-
-  // Example: "base/base.ninja". The string version will not be escaped, and
-  // will always have slashes for path separators.
-  OutputFile GetNinjaFileForTarget(const Target* target) const;
-
-  // Returns the name of the root .ninja file for the given toolchain.
-  OutputFile GetNinjaFileForToolchain(const Settings* settings) const;
-
-  // Given a source file relative to the source root, returns the output
-  // filename.
-  OutputFile GetOutputFileForSource(const Target* target,
-                                    const SourceFile& source,
-                                    SourceFileType type) const;
-
-  // Returns the filename produced by the given output.
-  //
-  // Some targets make multiple files (like a .dll and an import library). This
-  // function returns the name of the file other targets should depend on and
-  // link to (so in this example, the import library).
-  OutputFile GetTargetOutputFile(const Target* target) const;
-
-  // Returns the prefix for rules on the given toolchain. We need this to
-  // disambiguate a given rule for each toolchain.
-  std::string GetRulePrefix(const Settings* settings) const;
-
-  // Returns the name of the rule name for the given toolchain and file/target
-  // type.  Returns the empty string for source files with no command.
-  std::string GetRuleForSourceType(const Settings* settings,
-                                   SourceFileType type) const;
-
-  // Returns the relative directory in either slashes or the system separator
-  // from the ninja directory (e.g. "out/Debug") to the source root (e.g.
-  // "../.."). It has no terminating slash.
-  const std::string& build_to_src_no_last_slash() const {
-    return build_to_src_no_last_slash_;
-  }
-  const std::string& build_to_src_system_no_last_slash() const {
-    return build_to_src_system_no_last_slash_;
-  }
-
- private:
-  const BuildSettings* build_settings_;
-
-  std::string build_to_src_no_last_slash_;
-  std::string build_to_src_system_no_last_slash_;
-
-  DISALLOW_COPY_AND_ASSIGN(NinjaHelper);
-};
-
-#endif  // TOOLS_GN_NINJA_HELPER_H_