Add initial prototype for the GN meta-buildsystem.

tools/gn/build_settings.h

Index: tools/gn/build_settings.h
diff --git a/tools/gn/build_settings.h b/tools/gn/build_settings.h
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+++ b/tools/gn/build_settings.h
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+// 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_BUILD_SETTINGS_H_
+#define TOOLS_GN_BUILD_SETTINGS_H_
+
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "tools/gn/item_tree.h"
+#include "tools/gn/scope.h"
+#include "tools/gn/source_dir.h"
+#include "tools/gn/source_file.h"
+#include "tools/gn/target_manager.h"
+#include "tools/gn/toolchain_manager.h"
+
+// Settings for one build, which is one toplevel output directory. There
+// may be multiple Settings objects that refer to this, one for each toolchain.
+class BuildSettings {
+ public:
+  typedef base::Callback<void(const Target*)> TargetResolvedCallback;
+
+  BuildSettings();
+  ~BuildSettings();
+
+  // Absolute path of the source root on the local system. Everything is
+  // relative to this.
+  const base::FilePath& root_path() const { return root_path_; }
+  void set_root_path(const base::FilePath& r) { root_path_ = r; }
+
+  // When nonempty, specifies a parallel directory higherarchy in which to
+  // search for buildfiles if they're not found in the root higherarchy. This
+  // allows us to keep buildfiles in a separate tree during development.
+  const base::FilePath& secondary_source_path() const {
+    return secondary_source_path_;
+  }
+  void SetSecondarySourcePath(const SourceDir& d);
+
+  // Path of the python executable to run scripts with.
+  base::FilePath python_path() const { return python_path_; }
+  void set_python_path(const base::FilePath& p) { python_path_ = p; }
+
+  const SourceFile& build_config_file() const { return build_config_file_; }
+  void set_build_config_file(const SourceFile& f) { build_config_file_ = f; }
+
+  // The build directory is the root of all output files. The default toolchain
+  // files go into here, and non-default toolchains will have separate
+  // toolchain-specific root directories inside this.
+  const SourceDir& build_dir() const { return build_dir_; }
+  void SetBuildDir(const SourceDir& dir);
+
+  // The inverse of relative_build_dir, ending with a separator.
+  // Example: relative_build_dir_ = "out/Debug/" this will be "../../"
+  const std::string& build_to_source_dir_string() const {
+    return build_to_source_dir_string_;
+  }
+
+  // These accessors do not return const objects since the resulting objects
+  // are threadsafe. In this setting, we use constness primarily to ensure
+  // that the Settings object is used in a threadsafe manner. Although this
+  // violates the concept of logical constness, that's less important in our
+  // application, and actually implementing this in a way that preserves
+  // logical constness is cumbersome.
+  ItemTree& item_tree() const { return item_tree_; }
+  TargetManager& target_manager() const { return target_manager_; }
+  ToolchainManager& toolchain_manager() const { return toolchain_manager_; }
+
+  // Returns the full absolute OS path cooresponding to the given file in the
+  // root source tree.
+  base::FilePath GetFullPath(const SourceFile& file) const;
+  base::FilePath GetFullPath(const SourceDir& dir) const;
+
+  // Returns the absolute OS path inside the secondary source path. Will return
+  // an empty FilePath if the secondary source path is empty. When loading a
+  // buildfile, the GetFullPath should always be consulted first.
+  base::FilePath GetFullPathSecondary(const SourceFile& file) const;
+  base::FilePath GetFullPathSecondary(const SourceDir& dir) const;
+
+  // This is the callback to execute when a target is marked resolved. If we
+  // don't need to do anything, this will be null. When a target is resolved,
+  // this callback should be posted to the scheduler pool so the work is
+  // distributed properly.
+  const TargetResolvedCallback& target_resolved_callback() const {
+    return target_resolved_callback_;
+  }
+  void set_target_resolved_callback(const TargetResolvedCallback& cb) {
+    target_resolved_callback_ = cb;
+  }
+
+ private:
+  base::FilePath root_path_;
+  base::FilePath secondary_source_path_;
+  base::FilePath python_path_;
+
+  SourceFile build_config_file_;
+  SourceDir build_dir_;
+  std::string build_to_source_dir_string_;
+
+  TargetResolvedCallback target_resolved_callback_;
+
+  // See getters above.
+  mutable ItemTree item_tree_;
+  mutable TargetManager target_manager_;
+  mutable ToolchainManager toolchain_manager_;
+
+  DISALLOW_COPY_AND_ASSIGN(BuildSettings);
+};
+
+#endif  // TOOLS_GN_BUILD_SETTINGS_H_