Improve performance of base::ListValue::Append*

base/values.cc

 // Copyright (c) 2012 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.
 
 #include "base/values.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 1058 matching lines @@
 }
 
 bool ListValue::Set(size_t index, Value* in_value) {
   return Set(index, WrapUnique(in_value));
 }
 
 bool ListValue::Set(size_t index, std::unique_ptr<Value> in_value) {
   if (!in_value)
     return false;
 
-  if (index >= list_->size()) {
-    // Pad out any intermediate indexes with null settings
-    while (index > list_->size())
-      Append(MakeUnique<Value>());
-    Append(std::move(in_value));
-  } else {
-    (*list_)[index] = std::move(*in_value);
-  }
+  if (index >= list_->size())
+    list_->resize(index + 1);
+
+  (*list_)[index] = std::move(*in_value);
   return true;
 }
 
 bool ListValue::Get(size_t index, const Value** out_value) const {
   if (index >= list_->size())
     return false;
 
   if (out_value)
     *out_value = &(*list_)[index];
 
@@ skipping 130 matching lines @@
     *out_value = MakeUnique<Value>(std::move(*iter));
 
   return list_->erase(iter);
 }
 
 void ListValue::Append(std::unique_ptr<Value> in_value) {
   list_->push_back(std::move(*in_value));
 }
 
 void ListValue::AppendBoolean(bool in_value) {
-  Append(MakeUnique<Value>(in_value));
+  list_->emplace_back(in_value);
 }
 
 void ListValue::AppendInteger(int in_value) {
-  Append(MakeUnique<Value>(in_value));
+  list_->emplace_back(in_value);
 }
 
 void ListValue::AppendDouble(double in_value) {
-  Append(MakeUnique<Value>(in_value));
+  list_->emplace_back(in_value);
 }
 
 void ListValue::AppendString(StringPiece in_value) {
-  Append(MakeUnique<Value>(in_value));
+  list_->emplace_back(in_value);
 }
 
 void ListValue::AppendString(const string16& in_value) {
-  Append(MakeUnique<Value>(in_value));
+  list_->emplace_back(in_value);
 }
 
 void ListValue::AppendStrings(const std::vector<std::string>& in_values) {
-  for (std::vector<std::string>::const_iterator it = in_values.begin();
-       it != in_values.end(); ++it) {
-    AppendString(*it);
-  }
+  list_->reserve(list_->size() + in_values.size());
+  for (const auto& in_value : in_values)
+    list_->emplace_back(in_value);
 }
 
 void ListValue::AppendStrings(const std::vector<string16>& in_values) {
-  for (std::vector<string16>::const_iterator it = in_values.begin();
-       it != in_values.end(); ++it) {
-    AppendString(*it);
-  }
+  list_->reserve(list_->size() + in_values.size());
+  for (const auto& in_value : in_values)
+    list_->emplace_back(in_value);
 }
 
 bool ListValue::AppendIfNotPresent(std::unique_ptr<Value> in_value) {
   DCHECK(in_value);
   if (std::find(list_->begin(), list_->end(), *in_value) != list_->end())
     return false;
 
   list_->push_back(std::move(*in_value));
   return true;
 }
@@ skipping 37 matching lines @@
 }
 
 std::ostream& operator<<(std::ostream& out, const Value::Type& type) {
   if (static_cast<int>(type) < 0 ||
       static_cast<size_t>(type) >= arraysize(kTypeNames))
     return out << "Invalid Type (index = " << static_cast<int>(type) << ")";
   return out << Value::GetTypeName(type);
 }
 
 }  // namespace base