Avoid string copying in json.cc.

The following two methods:

  bool Json::HasStringValueForKey(const std::string& key) const;
  std::string Json::GetStringValueForKey(const std::string& key) const;

have been replaced with a single method:

  bool Json::GetStringValueForKey(const std::string& key,
                                  std::string* value) const;

to avoid copying possibly large strings.

BUG=8
R=roubert@google.com

Review URL: https://codereview.appspot.com/112940044

1 files changed, 25 insertions, 17 deletions

diff --git a/cpp/test/util/json_test.cc b/cpp/test/util/json_test.cc
index f6eb389..a3b9f80 100644
--- a/cpp/test/util/json_test.cc
+++ b/cpp/test/util/json_test.cc
@@ -32,8 +32,9 @@ TEST(JsonTest, EmptyStringIsNotValid) {
 TEST(JsonTest, EmptyDictionaryContainsNoKeys) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{}"));
-  EXPECT_FALSE(json.HasStringValueForKey("key"));
-  EXPECT_FALSE(json.HasStringValueForKey(std::string()));
+  std::string not_checked;
+  EXPECT_FALSE(json.GetStringValueForKey("key", &not_checked));
+  EXPECT_FALSE(json.GetStringValueForKey(std::string(), &not_checked));
 }
 
 TEST(JsonTest, InvalidJsonIsNotValid) {
@@ -44,35 +45,40 @@ TEST(JsonTest, InvalidJsonIsNotValid) {
 TEST(JsonTest, OneKeyIsValid) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{\"key\": \"value\"}"));
-  ASSERT_TRUE(json.HasStringValueForKey("key"));
-  EXPECT_EQ("value", json.GetStringValueForKey("key"));
+  std::string value;
+  EXPECT_TRUE(json.GetStringValueForKey("key", &value));
+  EXPECT_EQ("value", value);
 }
 
 TEST(JsonTest, EmptyStringKeyIsNotInObject) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{\"key\": \"value\"}"));
-  EXPECT_FALSE(json.HasStringValueForKey(std::string()));
+  std::string not_checked;
+  EXPECT_FALSE(json.GetStringValueForKey(std::string(), &not_checked));
 }
 
 TEST(JsonTest, EmptyKeyIsValid) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{\"\": \"value\"}"));
-  ASSERT_TRUE(json.HasStringValueForKey(std::string()));
-  EXPECT_EQ("value", json.GetStringValueForKey(std::string()));
+  std::string value;
+  EXPECT_TRUE(json.GetStringValueForKey(std::string(), &value));
+  EXPECT_EQ("value", value);
 }
 
 TEST(JsonTest, EmptyValueIsValid) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{\"key\": \"\"}"));
-  ASSERT_TRUE(json.HasStringValueForKey("key"));
-  EXPECT_TRUE(json.GetStringValueForKey("key").empty());
+  std::string value;
+  EXPECT_TRUE(json.GetStringValueForKey("key", &value));
+  EXPECT_TRUE(value.empty());
 }
 
 TEST(JsonTest, Utf8EncodingIsValid) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{\"key\": \"Ü\"}"));
-  ASSERT_TRUE(json.HasStringValueForKey("key"));
-  EXPECT_EQ("Ü", json.GetStringValueForKey("key"));
+  std::string value;
+  EXPECT_TRUE(json.GetStringValueForKey("key", &value));
+  EXPECT_EQ("Ü", value);
 }
 
 TEST(JsonTest, InvalidUtf8IsNotValid) {
@@ -89,11 +95,12 @@ TEST(JsonTest, NullInMiddleIsNotValid) {
 TEST(JsonTest, TwoKeysAreValid) {
   Json json;
   ASSERT_TRUE(json.ParseObject("{\"key1\": \"value1\", \"key2\": \"value2\"}"));
-  ASSERT_TRUE(json.HasStringValueForKey("key1"));
-  EXPECT_EQ("value1", json.GetStringValueForKey("key1"));
+  std::string value;
+  EXPECT_TRUE(json.GetStringValueForKey("key1", &value));
+  EXPECT_EQ("value1", value);
 
-  ASSERT_TRUE(json.HasStringValueForKey("key2"));
-  EXPECT_EQ("value2", json.GetStringValueForKey("key2"));
+  EXPECT_TRUE(json.GetStringValueForKey("key2", &value));
+  EXPECT_EQ("value2", value);
 }
 
 TEST(JsonTest, ListIsNotValid) {
@@ -122,8 +129,9 @@ TEST(JsonTest, DictionaryFound) {
   ASSERT_TRUE(json.ParseObject("{\"key\":{\"inner_key\":\"value\"}}"));
   ASSERT_TRUE(json.HasDictionaryValueForKey("key"));
   const Json& sub_json = json.GetDictionaryValueForKey("key");
-  ASSERT_TRUE(sub_json.HasStringValueForKey("inner_key"));
-  EXPECT_EQ("value", sub_json.GetStringValueForKey("inner_key"));
+  std::string value;
+  EXPECT_TRUE(sub_json.GetStringValueForKey("inner_key", &value));
+  EXPECT_EQ("value", value);
 }
 
 TEST(JsonTest, DictionariesHaveKeys) {