Add a UniqueVector class to GN

tools/gn/label_ptr.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_LABEL_PTR_H_
 #define TOOLS_GN_LABEL_PTR_H_
 
 #include <functional>
 
+#include "tools/gn/label.h"
+
+class Config;
 class ParseNode;
+class Target;
 
 // 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;
 
@@ skipping 52 matching lines @@
 // 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;
   }
 };
 
+// Default comparison operators -----------------------------------------------
+//
+// The default hash and comparison operators operate on the label, which should
+// always be valid, whereas the pointer is sometimes null.
+
+template<typename T> inline bool operator==(const LabelPtrPair<T>& a,
+                                            const LabelPtrPair<T>& b) {
+  return a.label == b.label;
+}
+
+template<typename T> inline bool operator<(const LabelPtrPair<T>& a,
+                                           const LabelPtrPair<T>& b) {
+  return a.label < b.label;
+}
+
+namespace BASE_HASH_NAMESPACE {
+
+#if defined(COMPILER_GCC)
+template<typename T> struct hash< LabelPtrPair<T> > {
+  std::size_t operator()(const LabelPtrPair<T>& v) const {
+    BASE_HASH_NAMESPACE::hash<Label> h;
+    return h(v.label);
+  }
+};
+#elif defined(COMPILER_MSVC)
+template<typename T>
+inline size_t hash_value(const LabelPtrPair<T>& v) {
+  return BASE_HASH_NAMESPACE::hash_value(v.label);
+}
+#endif  // COMPILER...
+
+}  // namespace BASE_HASH_NAMESPACE
+
 #endif  // TOOLS_GN_LABEL_PTR_H_