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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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// This file specifies a recursive data storage class called Value intended for
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// storing settings and other persistable data.
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// A Value represents something that can be stored in JSON or passed to/from
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// JavaScript. As such, it is NOT a generalized variant type, since only the
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// types supported by JavaScript/JSON are supported.
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// IN PARTICULAR this means that there is no support for int64 or unsigned
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// numbers. Writing JSON with such types would violate the spec. If you need
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// something like this, either use a double or make a string value containing
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// the number you want.
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#ifndef BASE_VALUES_H_
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#define BASE_VALUES_H_
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#include "base/base_export.h"
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#include "base/basictypes.h"
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#include "base/compiler_specific.h"
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#include "base/memory/scoped_ptr.h"
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#include "base/strings/string16.h"
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class DictionaryValue;
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class FundamentalValue;
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typedef std::vector<Value*> ValueVector;
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typedef std::map<std::string, Value*> ValueMap;
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// The Value class is the base class for Values. A Value can be instantiated
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// via the Create*Value() factory methods, or by directly creating instances of
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// See the file-level comment above for more information.
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class BASE_EXPORT Value {
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// Note: Do not add more types. See the file-level comment above for why.
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static Value* CreateNullValue();
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// DEPRECATED: Do not use the following 5 functions. Instead, use
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// new FundamentalValue or new StringValue.
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static FundamentalValue* CreateBooleanValue(bool in_value);
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static FundamentalValue* CreateIntegerValue(int in_value);
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static FundamentalValue* CreateDoubleValue(double in_value);
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static StringValue* CreateStringValue(const std::string& in_value);
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static StringValue* CreateStringValue(const string16& in_value);
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// Returns the type of the value stored by the current Value object.
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// Each type will be implemented by only one subclass of Value, so it's
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// safe to use the Type to determine whether you can cast from
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// Value* to (Implementing Class)*. Also, a Value object never changes
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// its type after construction.
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Type GetType() const { return type_; }
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// Returns true if the current object represents a given type.
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bool IsType(Type type) const { return type == type_; }
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// These methods allow the convenient retrieval of the contents of the Value.
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// If the current object can be converted into the given type, the value is
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// returned through the |out_value| parameter and true is returned;
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// otherwise, false is returned and |out_value| is unchanged.
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virtual bool GetAsBoolean(bool* out_value) const;
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virtual bool GetAsInteger(int* out_value) const;
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virtual bool GetAsDouble(double* out_value) const;
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virtual bool GetAsString(std::string* out_value) const;
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virtual bool GetAsString(string16* out_value) const;
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virtual bool GetAsString(const StringValue** out_value) const;
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virtual bool GetAsList(ListValue** out_value);
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virtual bool GetAsList(const ListValue** out_value) const;
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virtual bool GetAsDictionary(DictionaryValue** out_value);
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virtual bool GetAsDictionary(const DictionaryValue** out_value) const;
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// Note: Do not add more types. See the file-level comment above for why.
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// This creates a deep copy of the entire Value tree, and returns a pointer
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// to the copy. The caller gets ownership of the copy, of course.
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// Subclasses return their own type directly in their overrides;
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// this works because C++ supports covariant return types.
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virtual Value* DeepCopy() const;
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// Compares if two Value objects have equal contents.
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virtual bool Equals(const Value* other) const;
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// Compares if two Value objects have equal contents. Can handle NULLs.
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// NULLs are considered equal but different from Value::CreateNullValue().
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static bool Equals(const Value* a, const Value* b);
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// These aren't safe for end-users, but they are useful for subclasses.
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explicit Value(Type type);
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Value(const Value& that);
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Value& operator=(const Value& that);
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// FundamentalValue represents the simple fundamental types of values.
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class BASE_EXPORT FundamentalValue : public Value {
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explicit FundamentalValue(bool in_value);
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explicit FundamentalValue(int in_value);
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explicit FundamentalValue(double in_value);
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virtual ~FundamentalValue();
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// Overridden from Value:
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virtual bool GetAsBoolean(bool* out_value) const OVERRIDE;
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virtual bool GetAsInteger(int* out_value) const OVERRIDE;
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// Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
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virtual bool GetAsDouble(double* out_value) const OVERRIDE;
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virtual FundamentalValue* DeepCopy() const OVERRIDE;
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virtual bool Equals(const Value* other) const OVERRIDE;
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double double_value_;
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class BASE_EXPORT StringValue : public Value {
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// Initializes a StringValue with a UTF-8 narrow character string.
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explicit StringValue(const std::string& in_value);
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// Initializes a StringValue with a string16.
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explicit StringValue(const string16& in_value);
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virtual ~StringValue();
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// Returns |value_| as a pointer or reference.
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std::string* GetString();
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const std::string& GetString() const;
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// Overridden from Value:
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virtual bool GetAsString(std::string* out_value) const OVERRIDE;
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virtual bool GetAsString(string16* out_value) const OVERRIDE;
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virtual bool GetAsString(const StringValue** out_value) const OVERRIDE;
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virtual StringValue* DeepCopy() const OVERRIDE;
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virtual bool Equals(const Value* other) const OVERRIDE;
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class BASE_EXPORT BinaryValue: public Value {
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// Creates a BinaryValue with a null buffer and size of 0.
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// Creates a BinaryValue, taking ownership of the bytes pointed to by
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BinaryValue(scoped_ptr<char[]> buffer, size_t size);
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virtual ~BinaryValue();
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// For situations where you want to keep ownership of your buffer, this
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// factory method creates a new BinaryValue by copying the contents of the
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// buffer that's passed in.
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static BinaryValue* CreateWithCopiedBuffer(const char* buffer, size_t size);
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size_t GetSize() const { return size_; }
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char* GetBuffer() { return buffer_.get(); }
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const char* GetBuffer() const { return buffer_.get(); }
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// Overridden from Value:
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virtual BinaryValue* DeepCopy() const OVERRIDE;
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virtual bool Equals(const Value* other) const OVERRIDE;
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scoped_ptr<char[]> buffer_;
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DISALLOW_COPY_AND_ASSIGN(BinaryValue);
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// DictionaryValue provides a key-value dictionary with (optional) "path"
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// parsing for recursive access; see the comment at the top of the file. Keys
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// are |std::string|s and should be UTF-8 encoded.
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class BASE_EXPORT DictionaryValue : public Value {
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virtual ~DictionaryValue();
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// Overridden from Value:
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virtual bool GetAsDictionary(DictionaryValue** out_value) OVERRIDE;
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virtual bool GetAsDictionary(
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const DictionaryValue** out_value) const OVERRIDE;
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// Returns true if the current dictionary has a value for the given key.
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bool HasKey(const std::string& key) const;
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// Returns the number of Values in this dictionary.
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size_t size() const { return dictionary_.size(); }
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// Returns whether the dictionary is empty.
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bool empty() const { return dictionary_.empty(); }
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// Clears any current contents of this dictionary.
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// Sets the Value associated with the given path starting from this object.
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// A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
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// into the next DictionaryValue down. Obviously, "." can't be used
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// within a key, but there are no other restrictions on keys.
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// If the key at any step of the way doesn't exist, or exists but isn't
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// a DictionaryValue, a new DictionaryValue will be created and attached
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// to the path in that location.
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// Note that the dictionary takes ownership of the value referenced by
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// |in_value|, and therefore |in_value| must be non-NULL.
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void Set(const std::string& path, Value* in_value);
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// Convenience forms of Set(). These methods will replace any existing
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// value at that path, even if it has a different type.
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void SetBoolean(const std::string& path, bool in_value);
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void SetInteger(const std::string& path, int in_value);
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void SetDouble(const std::string& path, double in_value);
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void SetString(const std::string& path, const std::string& in_value);
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void SetString(const std::string& path, const string16& in_value);
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// Like Set(), but without special treatment of '.'. This allows e.g. URLs to
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void SetWithoutPathExpansion(const std::string& key, Value* in_value);
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// Convenience forms of SetWithoutPathExpansion().
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void SetBooleanWithoutPathExpansion(const std::string& path, bool in_value);
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void SetIntegerWithoutPathExpansion(const std::string& path, int in_value);
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void SetDoubleWithoutPathExpansion(const std::string& path, double in_value);
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void SetStringWithoutPathExpansion(const std::string& path,
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const std::string& in_value);
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void SetStringWithoutPathExpansion(const std::string& path,
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const string16& in_value);
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// Gets the Value associated with the given path starting from this object.
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// A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
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// into the next DictionaryValue down. If the path can be resolved
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// successfully, the value for the last key in the path will be returned
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// through the |out_value| parameter, and the function will return true.
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// Otherwise, it will return false and |out_value| will be untouched.
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// Note that the dictionary always owns the value that's returned.
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// |out_value| is optional and will only be set if non-NULL.
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bool Get(const std::string& path, const Value** out_value) const;
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bool Get(const std::string& path, Value** out_value);
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// These are convenience forms of Get(). The value will be retrieved
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// and the return value will be true if the path is valid and the value at
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// the end of the path can be returned in the form specified.
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// |out_value| is optional and will only be set if non-NULL.
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bool GetBoolean(const std::string& path, bool* out_value) const;
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bool GetInteger(const std::string& path, int* out_value) const;
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// Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
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bool GetDouble(const std::string& path, double* out_value) const;
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bool GetString(const std::string& path, std::string* out_value) const;
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bool GetString(const std::string& path, string16* out_value) const;
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bool GetStringASCII(const std::string& path, std::string* out_value) const;
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bool GetBinary(const std::string& path, const BinaryValue** out_value) const;
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bool GetBinary(const std::string& path, BinaryValue** out_value);
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bool GetDictionary(const std::string& path,
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const DictionaryValue** out_value) const;
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bool GetDictionary(const std::string& path, DictionaryValue** out_value);
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bool GetList(const std::string& path, const ListValue** out_value) const;
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bool GetList(const std::string& path, ListValue** out_value);
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// Like Get(), but without special treatment of '.'. This allows e.g. URLs to
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bool GetWithoutPathExpansion(const std::string& key,
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const Value** out_value) const;
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bool GetWithoutPathExpansion(const std::string& key, Value** out_value);
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bool GetBooleanWithoutPathExpansion(const std::string& key,
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bool* out_value) const;
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bool GetIntegerWithoutPathExpansion(const std::string& key,
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int* out_value) const;
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bool GetDoubleWithoutPathExpansion(const std::string& key,
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double* out_value) const;
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bool GetStringWithoutPathExpansion(const std::string& key,
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std::string* out_value) const;
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bool GetStringWithoutPathExpansion(const std::string& key,
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string16* out_value) const;
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bool GetDictionaryWithoutPathExpansion(
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const std::string& key,
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const DictionaryValue** out_value) const;
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bool GetDictionaryWithoutPathExpansion(const std::string& key,
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DictionaryValue** out_value);
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bool GetListWithoutPathExpansion(const std::string& key,
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const ListValue** out_value) const;
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bool GetListWithoutPathExpansion(const std::string& key,
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ListValue** out_value);
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// Removes the Value with the specified path from this dictionary (or one
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// of its child dictionaries, if the path is more than just a local key).
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// If |out_value| is non-NULL, the removed Value will be passed out via
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// |out_value|. If |out_value| is NULL, the removed value will be deleted.
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// This method returns true if |path| is a valid path; otherwise it will
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// return false and the DictionaryValue object will be unchanged.
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virtual bool Remove(const std::string& path, scoped_ptr<Value>* out_value);
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// Like Remove(), but without special treatment of '.'. This allows e.g. URLs
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// to be used as paths.
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virtual bool RemoveWithoutPathExpansion(const std::string& key,
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scoped_ptr<Value>* out_value);
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// Removes a path, clearing out all dictionaries on |path| that remain empty
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// after removing the value at |path|.
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virtual bool RemovePath(const std::string& path,
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scoped_ptr<Value>* out_value);
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// Makes a copy of |this| but doesn't include empty dictionaries and lists in
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// the copy. This never returns NULL, even if |this| itself is empty.
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DictionaryValue* DeepCopyWithoutEmptyChildren() const;
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// Merge |dictionary| into this dictionary. This is done recursively, i.e. any
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// sub-dictionaries will be merged as well. In case of key collisions, the
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// passed in dictionary takes precedence and data already present will be
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// replaced. Values within |dictionary| are deep-copied, so |dictionary| may
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// be freed any time after this call.
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void MergeDictionary(const DictionaryValue* dictionary);
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// Swaps contents with the |other| dictionary.
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virtual void Swap(DictionaryValue* other);
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// This class provides an iterator over both keys and values in the
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// dictionary. It can't be used to modify the dictionary.
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class BASE_EXPORT Iterator {
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explicit Iterator(const DictionaryValue& target);
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bool IsAtEnd() const { return it_ == target_.dictionary_.end(); }
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void Advance() { ++it_; }
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const std::string& key() const { return it_->first; }
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const Value& value() const { return *it_->second; }
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const DictionaryValue& target_;
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ValueMap::const_iterator it_;
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// Overridden from Value:
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virtual DictionaryValue* DeepCopy() const OVERRIDE;
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virtual bool Equals(const Value* other) const OVERRIDE;
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ValueMap dictionary_;
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DISALLOW_COPY_AND_ASSIGN(DictionaryValue);
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// This type of Value represents a list of other Value values.
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class BASE_EXPORT ListValue : public Value {
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typedef ValueVector::iterator iterator;
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typedef ValueVector::const_iterator const_iterator;
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virtual ~ListValue();
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// Clears the contents of this ListValue
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// Returns the number of Values in this list.
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size_t GetSize() const { return list_.size(); }
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// Returns whether the list is empty.
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bool empty() const { return list_.empty(); }
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// Sets the list item at the given index to be the Value specified by
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// the value given. If the index beyond the current end of the list, null
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// Values will be used to pad out the list.
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// Returns true if successful, or false if the index was negative or
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// the value is a null pointer.
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bool Set(size_t index, Value* in_value);
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// Gets the Value at the given index. Modifies |out_value| (and returns true)
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// only if the index falls within the current list range.
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// Note that the list always owns the Value passed out via |out_value|.
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// |out_value| is optional and will only be set if non-NULL.
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bool Get(size_t index, const Value** out_value) const;
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bool Get(size_t index, Value** out_value);
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// Convenience forms of Get(). Modifies |out_value| (and returns true)
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// only if the index is valid and the Value at that index can be returned
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// in the specified form.
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// |out_value| is optional and will only be set if non-NULL.
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bool GetBoolean(size_t index, bool* out_value) const;
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bool GetInteger(size_t index, int* out_value) const;
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// Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
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bool GetDouble(size_t index, double* out_value) const;
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bool GetString(size_t index, std::string* out_value) const;
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bool GetString(size_t index, string16* out_value) const;
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bool GetBinary(size_t index, const BinaryValue** out_value) const;
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bool GetBinary(size_t index, BinaryValue** out_value);
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bool GetDictionary(size_t index, const DictionaryValue** out_value) const;
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bool GetDictionary(size_t index, DictionaryValue** out_value);
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bool GetList(size_t index, const ListValue** out_value) const;
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bool GetList(size_t index, ListValue** out_value);
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// Removes the Value with the specified index from this list.
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// If |out_value| is non-NULL, the removed Value AND ITS OWNERSHIP will be
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// passed out via |out_value|. If |out_value| is NULL, the removed value will
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// be deleted. This method returns true if |index| is valid; otherwise
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// it will return false and the ListValue object will be unchanged.
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virtual bool Remove(size_t index, scoped_ptr<Value>* out_value);
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// Removes the first instance of |value| found in the list, if any, and
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// deletes it. |index| is the location where |value| was found. Returns false
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bool Remove(const Value& value, size_t* index);
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// Removes the element at |iter|. If |out_value| is NULL, the value will be
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// deleted, otherwise ownership of the value is passed back to the caller.
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// Returns an iterator pointing to the location of the element that
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// followed the erased element.
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iterator Erase(iterator iter, scoped_ptr<Value>* out_value);
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// Appends a Value to the end of the list.
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void Append(Value* in_value);
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// Convenience forms of Append.
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void AppendBoolean(bool in_value);
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void AppendInteger(int in_value);
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void AppendDouble(double in_value);
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void AppendString(const std::string& in_value);
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void AppendString(const string16& in_value);
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void AppendStrings(const std::vector<std::string>& in_values);
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void AppendStrings(const std::vector<string16>& in_values);
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// Appends a Value if it's not already present. Takes ownership of the
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// |in_value|. Returns true if successful, or false if the value was already
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// present. If the value was already present the |in_value| is deleted.
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bool AppendIfNotPresent(Value* in_value);
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// Insert a Value at index.
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// Returns true if successful, or false if the index was out of range.
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bool Insert(size_t index, Value* in_value);
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// Searches for the first instance of |value| in the list using the Equals
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// method of the Value type.
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// Returns a const_iterator to the found item or to end() if none exists.
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const_iterator Find(const Value& value) const;
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// Swaps contents with the |other| list.
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virtual void Swap(ListValue* other);
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iterator begin() { return list_.begin(); }
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iterator end() { return list_.end(); }
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const_iterator begin() const { return list_.begin(); }
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const_iterator end() const { return list_.end(); }
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// Overridden from Value:
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virtual bool GetAsList(ListValue** out_value) OVERRIDE;
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virtual bool GetAsList(const ListValue** out_value) const OVERRIDE;
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virtual ListValue* DeepCopy() const OVERRIDE;
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virtual bool Equals(const Value* other) const OVERRIDE;
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DISALLOW_COPY_AND_ASSIGN(ListValue);
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// This interface is implemented by classes that know how to serialize and
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// deserialize Value objects.
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class BASE_EXPORT ValueSerializer {
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virtual ~ValueSerializer();
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virtual bool Serialize(const Value& root) = 0;
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// This method deserializes the subclass-specific format into a Value object.
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// If the return value is non-NULL, the caller takes ownership of returned
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// Value. If the return value is NULL, and if error_code is non-NULL,
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// error_code will be set with the underlying error.
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// If |error_message| is non-null, it will be filled in with a formatted
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// error message including the location of the error if appropriate.
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virtual Value* Deserialize(int* error_code, std::string* error_str) = 0;
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// Stream operator so Values can be used in assertion statements. In order that
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// gtest uses this operator to print readable output on test failures, we must
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// override each specific type. Otherwise, the default template implementation
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// is preferred over an upcast.
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BASE_EXPORT std::ostream& operator<<(std::ostream& out, const Value& value);
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BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
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const FundamentalValue& value) {
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return out << static_cast<const Value&>(value);
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BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
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const StringValue& value) {
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return out << static_cast<const Value&>(value);
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BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
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const DictionaryValue& value) {
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return out << static_cast<const Value&>(value);
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BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
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const ListValue& value) {
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return out << static_cast<const Value&>(value);
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#endif // BASE_VALUES_H_