Add initial prototype for the GN meta-buildsystem.

tools/gn/scheduler.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_SCHEDULER_H_
+#define TOOLS_GN_SCHEDULER_H_
+
+#include "base/atomic_ref_count.h"
+#include "base/basictypes.h"
+#include "base/message_loop/message_loop.h"
+#include "base/run_loop.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/sequenced_worker_pool.h"
+#include "tools/gn/input_file_manager.h"
+
+class Target;
+
+// Maintains the thread pool and error state.
+class Scheduler {
+ public:
+  Scheduler();
+  ~Scheduler();
+
+  bool Run();
+
+  base::MessageLoop* main_loop() { return &main_loop_; }
+  base::SequencedWorkerPool* pool() { return pool_; }
+
+  InputFileManager* input_file_manager() { return input_file_manager_; }
+
+  bool verbose_logging() const { return verbose_logging_; }
+  void set_verbose_logging(bool v) { verbose_logging_ = v; }
+
+  // TODO(brettw) data race on this access (benign?).
+  bool is_failed() const { return is_failed_; }
+
+  void Log(const std::string& verb, const std::string& msg);
+  void FailWithError(const Err& err);
+
+  void ScheduleWork(const base::Closure& work);
+
+  void ScheduleTargetFileWrite(const Target* target);
+
+  // Declares that the given file was read and affected the build output.
+  //
+  // TODO(brettw) this is global rather than per-BuildSettings. If we
+  // start using >1 build settings, then we probably want this to take a
+  // BuildSettings object so we know the depdency on a per-build basis.
+  void AddGenDependency(const SourceFile& source_file);
+  std::vector<SourceFile> GetGenDependencies() const;
+
+  // We maintain a count of the things we need to do that works like a
+  // refcount. When this reaches 0, the program exits.
+  void IncrementWorkCount();
+  void DecrementWorkCount();
+
+ private:
+  void LogOnMainThread(const std::string& verb, const std::string& msg);
+  void FailWithErrorOnMainThread(const Err& err);
+
+  void DoTargetFileWrite(const Target* target);
+
+  void DoWork(const base::Closure& closure);
+
+  void OnComplete();
+
+  base::MessageLoop main_loop_;
+  scoped_refptr<base::SequencedWorkerPool> pool_;
+
+  scoped_refptr<InputFileManager> input_file_manager_;
+
+  base::RunLoop runner_;
+
+  bool verbose_logging_;
+
+  base::AtomicRefCount work_count_;
+
+  mutable base::Lock lock_;
+  bool is_failed_;
+
+  // Additional input dependencies. Protected by the lock.
+  std::vector<SourceFile> gen_dependencies_;
+
+  DISALLOW_COPY_AND_ASSIGN(Scheduler);
+};
+
+extern Scheduler* g_scheduler;
+
+#endif  // TOOLS_GN_SCHEDULER_H_
+