Use StringPiece more in base::Value interfaces.

base/values.h

 // 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.
 
 // This file specifies a recursive data storage class called Value intended for
 // storing settings and other persistable data.
 //
 // A Value represents something that can be stored in JSON or passed to/from
 // JavaScript. As such, it is NOT a generalized variant type, since only the
 // types supported by JavaScript/JSON are supported.
@@ skipping 131 matching lines @@
   union {
     bool boolean_value_;
     int integer_value_;
     double double_value_;
   };
 };
 
 class BASE_EXPORT StringValue : public Value {
  public:
   // Initializes a StringValue with a UTF-8 narrow character string.
-  explicit StringValue(const std::string& in_value);
+  explicit StringValue(StringPiece in_value);
 
   // Initializes a StringValue with a string16.
   explicit StringValue(const string16& in_value);

[dcheng, 2016/08/25 07:39:34]

I didn't bother with string16, since calling this with a literal is currently
much more rare. The only place this is likely to happen is on Windows. Perhaps
this will change once we have Unicode literals?

 
   ~StringValue() override;
 
   // Returns |value_| as a pointer or reference.
   std::string* GetString();
   const std::string& GetString() const;
 
   // Overridden from Value:
   bool GetAsString(std::string* out_value) const override;
   bool GetAsString(string16* out_value) const override;
@@ skipping 50 matching lines @@
   static std::unique_ptr<DictionaryValue> From(std::unique_ptr<Value> value);
 
   DictionaryValue();
   ~DictionaryValue() override;
 
   // Overridden from Value:
   bool GetAsDictionary(DictionaryValue** out_value) override;
   bool GetAsDictionary(const DictionaryValue** out_value) const override;
 
   // Returns true if the current dictionary has a value for the given key.
-  bool HasKey(const std::string& key) const;
+  bool HasKey(StringPiece key) const;
 
   // Returns the number of Values in this dictionary.
   size_t size() const { return dictionary_.size(); }
 
   // Returns whether the dictionary is empty.
   bool empty() const { return dictionary_.empty(); }
 
   // Clears any current contents of this dictionary.
   void Clear();
 
   // Sets the Value associated with the given path starting from this object.
   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
   // into the next DictionaryValue down.  Obviously, "." can't be used
   // within a key, but there are no other restrictions on keys.
   // If the key at any step of the way doesn't exist, or exists but isn't
   // a DictionaryValue, a new DictionaryValue will be created and attached
   // to the path in that location. |in_value| must be non-null.
-  void Set(const std::string& path, std::unique_ptr<Value> in_value);
+  void Set(StringPiece path, std::unique_ptr<Value> in_value);
   // Deprecated version of the above. TODO(estade): remove.
-  void Set(const std::string& path, Value* in_value);
+  void Set(StringPiece path, Value* in_value);
 
   // Convenience forms of Set().  These methods will replace any existing
   // value at that path, even if it has a different type.
-  void SetBoolean(const std::string& path, bool in_value);
-  void SetInteger(const std::string& path, int in_value);
-  void SetDouble(const std::string& path, double in_value);
-  void SetString(const std::string& path, const std::string& in_value);
-  void SetString(const std::string& path, const string16& in_value);
+  void SetBoolean(StringPiece path, bool in_value);
+  void SetInteger(StringPiece path, int in_value);
+  void SetDouble(StringPiece path, double in_value);
+  void SetString(StringPiece path, StringPiece in_value);
+  void SetString(StringPiece path, const string16& in_value);
 
   // Like Set(), but without special treatment of '.'.  This allows e.g. URLs to
   // be used as paths.
-  void SetWithoutPathExpansion(const std::string& key,
+  void SetWithoutPathExpansion(StringPiece key,
                                std::unique_ptr<Value> in_value);
   // Deprecated version of the above. TODO(estade): remove.
-  void SetWithoutPathExpansion(const std::string& key, Value* in_value);
+  void SetWithoutPathExpansion(StringPiece key, Value* in_value);
 
   // Convenience forms of SetWithoutPathExpansion().
-  void SetBooleanWithoutPathExpansion(const std::string& path, bool in_value);
-  void SetIntegerWithoutPathExpansion(const std::string& path, int in_value);
-  void SetDoubleWithoutPathExpansion(const std::string& path, double in_value);
-  void SetStringWithoutPathExpansion(const std::string& path,
-                                     const std::string& in_value);
-  void SetStringWithoutPathExpansion(const std::string& path,
+  void SetBooleanWithoutPathExpansion(StringPiece path, bool in_value);
+  void SetIntegerWithoutPathExpansion(StringPiece path, int in_value);
+  void SetDoubleWithoutPathExpansion(StringPiece path, double in_value);
+  void SetStringWithoutPathExpansion(StringPiece path, StringPiece in_value);
+  void SetStringWithoutPathExpansion(StringPiece path,
                                      const string16& in_value);
 
   // Gets the Value associated with the given path starting from this object.
   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
   // into the next DictionaryValue down.  If the path can be resolved
   // successfully, the value for the last key in the path will be returned
   // through the |out_value| parameter, and the function will return true.
   // Otherwise, it will return false and |out_value| will be untouched.
   // Note that the dictionary always owns the value that's returned.
   // |out_value| is optional and will only be set if non-NULL.
   bool Get(StringPiece path, const Value** out_value) const;
   bool Get(StringPiece path, Value** out_value);
 
   // These are convenience forms of Get().  The value will be retrieved
   // and the return value will be true if the path is valid and the value at
   // the end of the path can be returned in the form specified.
   // |out_value| is optional and will only be set if non-NULL.
-  bool GetBoolean(const std::string& path, bool* out_value) const;
-  bool GetInteger(const std::string& path, int* out_value) const;
+  bool GetBoolean(StringPiece path, bool* out_value) const;
+  bool GetInteger(StringPiece path, int* out_value) const;
   // Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
   // doubles.
-  bool GetDouble(const std::string& path, double* out_value) const;
-  bool GetString(const std::string& path, std::string* out_value) const;
-  bool GetString(const std::string& path, string16* out_value) const;
-  bool GetStringASCII(const std::string& path, std::string* out_value) const;
-  bool GetBinary(const std::string& path, const BinaryValue** out_value) const;
-  bool GetBinary(const std::string& path, BinaryValue** out_value);
+  bool GetDouble(StringPiece path, double* out_value) const;
+  bool GetString(StringPiece path, std::string* out_value) const;
+  bool GetString(StringPiece path, string16* out_value) const;
+  bool GetStringASCII(StringPiece path, std::string* out_value) const;
+  bool GetBinary(StringPiece path, const BinaryValue** out_value) const;
+  bool GetBinary(StringPiece path, BinaryValue** out_value);
   bool GetDictionary(StringPiece path,
                      const DictionaryValue** out_value) const;
   bool GetDictionary(StringPiece path, DictionaryValue** out_value);
-  bool GetList(const std::string& path, const ListValue** out_value) const;
-  bool GetList(const std::string& path, ListValue** out_value);
+  bool GetList(StringPiece path, const ListValue** out_value) const;
+  bool GetList(StringPiece path, ListValue** out_value);
 
   // Like Get(), but without special treatment of '.'.  This allows e.g. URLs to
   // be used as paths.
-  bool GetWithoutPathExpansion(const std::string& key,
-                               const Value** out_value) const;
-  bool GetWithoutPathExpansion(const std::string& key, Value** out_value);
-  bool GetBooleanWithoutPathExpansion(const std::string& key,
-                                      bool* out_value) const;
-  bool GetIntegerWithoutPathExpansion(const std::string& key,
-                                      int* out_value) const;
-  bool GetDoubleWithoutPathExpansion(const std::string& key,
-                                     double* out_value) const;
-  bool GetStringWithoutPathExpansion(const std::string& key,
+  bool GetWithoutPathExpansion(StringPiece key, const Value** out_value) const;
+  bool GetWithoutPathExpansion(StringPiece key, Value** out_value);
+  bool GetBooleanWithoutPathExpansion(StringPiece key, bool* out_value) const;
+  bool GetIntegerWithoutPathExpansion(StringPiece key, int* out_value) const;
+  bool GetDoubleWithoutPathExpansion(StringPiece key, double* out_value) const;
+  bool GetStringWithoutPathExpansion(StringPiece key,
                                      std::string* out_value) const;
-  bool GetStringWithoutPathExpansion(const std::string& key,
+  bool GetStringWithoutPathExpansion(StringPiece key,
                                      string16* out_value) const;
   bool GetDictionaryWithoutPathExpansion(
-      const std::string& key,
+      StringPiece key,
       const DictionaryValue** out_value) const;
-  bool GetDictionaryWithoutPathExpansion(const std::string& key,
+  bool GetDictionaryWithoutPathExpansion(StringPiece key,
                                          DictionaryValue** out_value);
-  bool GetListWithoutPathExpansion(const std::string& key,
+  bool GetListWithoutPathExpansion(StringPiece key,
                                    const ListValue** out_value) const;
-  bool GetListWithoutPathExpansion(const std::string& key,
-                                   ListValue** out_value);
+  bool GetListWithoutPathExpansion(StringPiece key, ListValue** out_value);
 
   // Removes the Value with the specified path from this dictionary (or one
   // of its child dictionaries, if the path is more than just a local key).
   // If |out_value| is non-NULL, the removed Value will be passed out via
   // |out_value|.  If |out_value| is NULL, the removed value will be deleted.
   // This method returns true if |path| is a valid path; otherwise it will
   // return false and the DictionaryValue object will be unchanged.
-  virtual bool Remove(const std::string& path,
-                      std::unique_ptr<Value>* out_value);
+  virtual bool Remove(StringPiece path, std::unique_ptr<Value>* out_value);
 
   // Like Remove(), but without special treatment of '.'.  This allows e.g. URLs
   // to be used as paths.
-  virtual bool RemoveWithoutPathExpansion(const std::string& key,
+  virtual bool RemoveWithoutPathExpansion(StringPiece key,
                                           std::unique_ptr<Value>* out_value);
 
   // Removes a path, clearing out all dictionaries on |path| that remain empty
   // after removing the value at |path|.
-  virtual bool RemovePath(const std::string& path,
-                          std::unique_ptr<Value>* out_value);
+  virtual bool RemovePath(StringPiece path, std::unique_ptr<Value>* out_value);
 
   // Makes a copy of |this| but doesn't include empty dictionaries and lists in
   // the copy.  This never returns NULL, even if |this| itself is empty.
   std::unique_ptr<DictionaryValue> DeepCopyWithoutEmptyChildren() const;
 
   // Merge |dictionary| into this dictionary. This is done recursively, i.e. any
   // sub-dictionaries will be merged as well. In case of key collisions, the
   // passed in dictionary takes precedence and data already present will be
   // replaced. Values within |dictionary| are deep-copied, so |dictionary| may
   // be freed any time after this call.
@@ skipping 109 matching lines @@
 
   // Appends a Value to the end of the list.
   void Append(std::unique_ptr<Value> in_value);
   // Deprecated version of the above. TODO(estade): remove.
   void Append(Value* in_value);
 
   // Convenience forms of Append.
   void AppendBoolean(bool in_value);
   void AppendInteger(int in_value);
   void AppendDouble(double in_value);
-  void AppendString(const std::string& in_value);
+  void AppendString(StringPiece in_value);
   void AppendString(const string16& in_value);
   void AppendStrings(const std::vector<std::string>& in_values);
   void AppendStrings(const std::vector<string16>& in_values);
 
   // Appends a Value if it's not already present. Takes ownership of the
   // |in_value|. Returns true if successful, or false if the value was already
   // present. If the value was already present the |in_value| is deleted.
   bool AppendIfNotPresent(Value* in_value);
 
   // Insert a Value at index.
@@ skipping 77 matching lines @@
 }
 
 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
                                             const ListValue& value) {
   return out << static_cast<const Value&>(value);
 }
 
 }  // namespace base
 
 #endif  // BASE_VALUES_H_