GN threading refactor

tools/gn/item_tree.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_ITEM_TREE_H_
-#define TOOLS_GN_ITEM_TREE_H_
-
-#include "base/containers/hash_tables.h"
-#include "base/memory/scoped_ptr.h"
-#include "base/synchronization/lock.h"
-#include "tools/gn/label.h"
-
-class BuildSettings;
-class Err;
-class Item;
-class ItemNode;
-
-// Represents the full dependency tree if labeled items in the system.
-// Generally you will interact with this through the target manager, etc.
-//
-// There are two modes for filling out the dependency tree:
-//
-// - In greedy mode, every target we encounter will be generated. This means
-//   that we'll recursively load all of its subdependencies. So if you have
-//   a build file that's loaded for any reason, all targets in that build file
-//   will be generated.
-//
-// - In non-greedy mode, we'll only generate and load dependncies for targets
-//   that have the should_generate bit set. This allows us to load the minimal
-//   set of buildfiles required for one or more targets.
-//
-// The main build is generally run in greedy mode, since people expect to be
-// be able to write random tests and have them show up in the output. We'll
-// switch into non-greed mode when doing diagnostics (like displaying the
-// dependency tree on the command line) and for dependencies on targets in
-// other toolchains. The toolchain behavior is important, if target A depends
-// on B with an alternate toolchain, it doesn't mean we should recursively
-// generate all targets in the buildfile just to get B: we should generate the
-// and load the minimum number of files in order to resolve B.
-class ItemTree {
- public:
-  ItemTree();
-  ~ItemTree();
-
-  // This lock must be held when calling the "Locked" functions below.
-  base::Lock& lock() const { return lock_; }
-
-  // Returns NULL if the item is not found.
-  //
-  // The lock must be held.
-  ItemNode* GetExistingNodeLocked(const Label& label);
-
-  // There must not be an item with this label in the tree already. Takes
-  // ownership of the pointer.
-  //
-  // The lock must be held.
-  void AddNodeLocked(ItemNode* node);
-
-  // Mark the given item as being defined. If it has no unresolved
-  // dependencies, it will be marked resolved, and the resolved state will be
-  // recursively pushed into the dependency tree. Returns an error if there was
-  // an error.
-  bool MarkItemDefinedLocked(const BuildSettings* build_settings,
-                             const Label& label,
-                             Err* err);
-
-  // Fills the given vector with all known items.
-  void GetAllItemNodesLocked(std::vector<const ItemNode*>* dest) const;
-  void GetAllItemsLocked(std::vector<const Item*>* dest) const;
-
-  // Returns an error if there are unresolved dependencies, or no error if
-  // there aren't.
-  //
-  // The lock should not be held.
-  Err CheckForBadItems() const;
-
- private:
-  void MarkItemResolvedLocked(ItemNode* node);
-
-  // Given a set of unresolved nodes, looks for cycles and returns the error
-  // message describing any cycles it found.
-  std::string CheckForCircularDependenciesLocked(
-      const std::vector<const ItemNode*>& bad_nodes) const;
-
-  mutable base::Lock lock_;
-
-  typedef base::hash_map<Label, ItemNode*> StringToNodeHash;
-  StringToNodeHash items_;  // Owning pointer.
-
-  DISALLOW_COPY_AND_ASSIGN(ItemTree);
-};
-
-#endif  // TOOLS_GN_ITEM_TREE_H_