GN threading refactor

tools/gn/item_node.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_NODE_H_
-#define TOOLS_GN_ITEM_NODE_H_
-
-#include <map>
-#include <vector>
-
-#include "base/basictypes.h"
-#include "base/callback.h"
-#include "base/memory/scoped_ptr.h"
-#include "tools/gn/location.h"
-
-class BuildSettings;
-class Err;
-class Item;
-
-// Represents a node in the depdency tree. It references an Item which is
-// the actual thing.
-//
-// The items and nodes are split apart so that the ItemTree can manipulate
-// the dependencies one one thread while the Item itself is been modified on
-// another.
-class ItemNode {
- public:
-  // The state of this node. As more of the load progresses, we'll move
-  // downward in this list toward the resolved state.
-  enum State {
-    // Another item has referenced this one by name, but we have not yet
-    // encountered its definition.
-    REFERENCED = 0,
-
-    // We've seen the definition of this item but have not requested that its
-    // dependencies be loaded. In non-greedy generation mode (see item_tree.h)
-    // some nodes will stay in this state forever as long as they're not needed
-    // for anything that is required.
-    DEFINED,
-
-    // The item has been defined and we've requested that all of the
-    // dependencies be loaded. Not all of the dependencies have been resolved,
-    // however, and we're still waiting on some build files to be run (or
-    // perhaps there are undefined dependencies).
-    PENDING_DEPS,
-
-    // All of this item's transitive dependencies have been found and
-    // resolved.
-    RESOLVED,
-  };
-
-  // Stores a set of ItemNodes and the associated range that the dependency
-  // was added from.
-  typedef std::map<ItemNode*, LocationRange> ItemNodeMap;
-
-  // Takes ownership of the pointer.
-  // Initial state will be REFERENCED.
-  ItemNode(Item* i);
-  ~ItemNode();
-
-  State state() const { return state_; }
-
-  // This closure will be executed when the item is resolved and it has the
-  // should_generate flag set.
-  void set_resolved_closure(const base::Closure& closure) {
-    resolved_closure_ = closure;
-  }
-
-  const Item* item() const { return item_.get(); }
-  Item* item() { return item_.get(); }
-
-  // True if this item should be generated. In greedy mode, this will alwyas
-  // be set. Otherwise, this bit will be "pushed" through the tree to
-  // generate the minimum set of targets required for some special base target.
-  // Initialized to false.
-  //
-  // If this item has been defined, setting this flag will schedule the load
-  // of dependent nodes and also set their should_generate bits.
-  bool should_generate() const { return should_generate_; }
-  bool SetShouldGenerate(const BuildSettings* build_settings, Err* err);
-
-  // Where this was created from, which might be when it was generated or
-  // when it was first referenced from another target.
-  const LocationRange& originally_referenced_from_here() const {
-    return originally_referenced_from_here_;
-  }
-  void set_originally_referenced_from_here(const LocationRange& r) {
-    originally_referenced_from_here_ = r;
-  }
-
-  // Where this was generated from. This will be empty for items that have
-  // been referenced but not generated. Note that this has to be one the
-  // ItemNode because it can be changing from multiple threads and we need
-  // to be sure that access is serialized.
-  const LocationRange& generated_from_here() const {
-    return generated_from_here_;
-  }
-  void set_generated_from_here(const LocationRange& r) {
-    generated_from_here_ = r;
-  }
-
-  const ItemNodeMap& direct_dependencies() const {
-    return direct_dependencies_;
-  }
-  const ItemNodeMap& unresolved_dependencies() const {
-    return unresolved_dependencies_;
-  }
-
-  bool AddDependency(const BuildSettings* build_settings,
-                     const LocationRange& specified_from_here,
-                     ItemNode* node,
-                     Err* err);
-
-  // Removes the given dependency from the unresolved list. Does not do
-  // anything else to update waiters.
-  void MarkDirectDependencyResolved(ItemNode* node);
-
-  // Destructively retrieve the set of waiting nodes.
-  void SwapOutWaitingDependencySet(ItemNodeMap* out_map);
-
-  // Marks this item state as defined (see above). If the should generate
-  // flag is set, this will schedule a load of the dependencies and
-  // automatically transition to the PENDING_DEPS state.
-  bool SetDefined(const BuildSettings* build_settings, Err* err);
-
-  // Marks this item state as resolved (see above).
-  void SetResolved();
-
- private:
-  // Schedules loading the dependencies of this node. The current state must
-  // be DEFINED, and this call will transition the state to PENDING_DEPS.
-  //
-  // Requesting deps can fail. On failure returns false and sets the err.
-  bool ScheduleDepsLoad(const BuildSettings* build_settings, Err* err);
-
-  State state_;
-  scoped_ptr<Item> item_;
-  bool should_generate_;  // See getter above.
-
-  LocationRange originally_referenced_from_here_;
-  LocationRange generated_from_here_;
-
-  // What to run when this item is resolved.
-  base::Closure resolved_closure_;
-
-  // Everything this item directly depends on.
-  ItemNodeMap direct_dependencies_;
-
-  // Unresolved things this item directly depends on.
-  ItemNodeMap unresolved_dependencies_;
-
-  // These items are waiting on us to be resolved before they can be
-  // resolved. This is the backpointer for unresolved_dependencies_.
-  ItemNodeMap waiting_on_resolution_;
-
-  DISALLOW_COPY_AND_ASSIGN(ItemNode);
-};
-
-#endif  // TOOLS_GN_ITEM_NODE_H_