GN: Separately track labels and origins for lists of stuff

tools/gn/label_ptr.h

Index: tools/gn/label_ptr.h
diff --git a/tools/gn/label_ptr.h b/tools/gn/label_ptr.h
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+++ b/tools/gn/label_ptr.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_LABEL_PTR_H_
+#define TOOLS_GN_LABEL_PTR_H_
+
+#include <functional>
+
+class ParseNode;
+
+// Structure that holds a labeled "thing". This is used for various places
+// where we need to store lists of targets or configs. We sometimes populate
+// the pointers on another thread from where we compute the labels, so this
+// structure lets us save them separately. This also allows us to store the
+// location of the thing that added this dependency.
+template<typename T>
+struct LabelPtrPair {
+  typedef T DestType;
+
+  LabelPtrPair() : label(), ptr(NULL), origin(NULL) {}
+
+  // This contructor is typically used in unit tests, it extracts the label
+  // automatically from a given pointer.
+  explicit LabelPtrPair(const T* p) : label(p->label()), ptr(p), origin(NULL) {
+  }
+
+  ~LabelPtrPair() {}
+
+  Label label;
+  const T* ptr;  // May be NULL.
+  const ParseNode* origin;  // May be NULL.
+};
+
+typedef LabelPtrPair<Config> LabelConfigPair;
+typedef LabelPtrPair<Target> LabelTargetPair;
+
+typedef std::vector<LabelConfigPair> LabelConfigVector;
+typedef std::vector<LabelTargetPair> LabelTargetVector;
+
+// Comparison and search functions ---------------------------------------------
+
+// To do a brute-force search by label:
+// std::find_if(vect.begin(), vect.end(), LabelPtrLabelEquals<Config>(label));
+template<typename T>
+struct LabelPtrLabelEquals : public std::unary_function<Label, bool> {
+  explicit LabelPtrLabelEquals(const Label& l) : label(l) {}
+
+  bool operator()(const LabelPtrPair<T>& arg) const {
+    return arg.label == label;
+  }
+
+  const Label& label;
+};
+
+// To do a brute-force search by object pointer:
+// std::find_if(vect.begin(), vect.end(), LabelPtrLabelEquals<Config>(config));
+template<typename T>
+struct LabelPtrPtrEquals : public std::unary_function<T, bool> {
+  explicit LabelPtrPtrEquals(const T* p) : ptr(p) {}
+
+  bool operator()(const LabelPtrPair<T>& arg) const {
+    return arg.ptr == ptr;
+  }
+
+  const T* ptr;
+};
+
+// To sort by label:
+// std::sort(vect.begin(), vect.end(), LabelPtrLabelLess<Config>());
+template<typename T>
+struct LabelPtrLabelLess : public std::binary_function<LabelPtrPair<T>,
+                                                       LabelPtrPair<T>,
+                                                       bool> {
+  bool operator()(const LabelPtrPair<T>& a, const LabelPtrPair<T>& b) const {
+    return a.label < b.label;
+  }
+};
+
+#endif  // TOOLS_GN_LABEL_PTR_H_