base/values.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // This file specifies a recursive data storage class called Value intended for
   6 // storing settings and other persistable data.
   7 //
   8 // A Value represents something that can be stored in JSON or passed to/from
   9 // JavaScript. As such, it is NOT a generalized variant type, since only the
  10 // types supported by JavaScript/JSON are supported.
  11 //
  12 // IN PARTICULAR this means that there is no support for int64 or unsigned
  13 // numbers. Writing JSON with such types would violate the spec. If you need
  14 // something like this, either use a double or make a string value containing
  15 // the number you want.
  16
  17 #ifndef BASE_VALUES_H_
  18 #define BASE_VALUES_H_
  19
  20 #include <iterator>
  21 #include <map>
  22 #include <string>
  23 #include <vector>
  24
  25 #include "base/base_export.h"
  26 #include "base/basictypes.h"
  27 #include "base/compiler_specific.h"
  28 #include "base/memory/scoped_ptr.h"
  29 #include "base/strings/string16.h"
  30
  31 // This file declares "using base::Value", etc. at the bottom, so that
  32 // current code can use these classes without the base namespace. In
  33 // new code, please always use base::Value, etc. or add your own
  34 // "using" declaration.
  35 // http://crbug.com/88666
  36 namespace base {
  37
  38 class BinaryValue;
  39 class DictionaryValue;
  40 class FundamentalValue;
  41 class ListValue;
  42 class StringValue;
  43 class Value;
  44
  45 typedef std::vector<Value*> ValueVector;
  46 typedef std::map<std::string, Value*> ValueMap;
  47
  48 // The Value class is the base class for Values. A Value can be instantiated
  49 // via the Create*Value() factory methods, or by directly creating instances of
  50 // the subclasses.
  51 //
  52 // See the file-level comment above for more information.
  53 class BASE_EXPORT Value {
  54  public:
  55   enum Type {
  56     TYPE_NULL = 0,
  57     TYPE_BOOLEAN,
  58     TYPE_INTEGER,
  59     TYPE_DOUBLE,
  60     TYPE_STRING,
  61     TYPE_BINARY,
  62     TYPE_DICTIONARY,
  63     TYPE_LIST
  64     // Note: Do not add more types. See the file-level comment above for why.
  65   };
  66
  67   virtual ~Value();
  68
  69   static Value* CreateNullValue();
  70   // DEPRECATED: Do not use the following 5 functions. Instead, use
  71   // new FundamentalValue or new StringValue.
  72   static FundamentalValue* CreateBooleanValue(bool in_value);
  73   static FundamentalValue* CreateIntegerValue(int in_value);
  74   static FundamentalValue* CreateDoubleValue(double in_value);
  75   static StringValue* CreateStringValue(const std::string& in_value);
  76   static StringValue* CreateStringValue(const string16& in_value);
  77
  78   // Returns the type of the value stored by the current Value object.
  79   // Each type will be implemented by only one subclass of Value, so it's
  80   // safe to use the Type to determine whether you can cast from
  81   // Value* to (Implementing Class)*.  Also, a Value object never changes
  82   // its type after construction.
  83   Type GetType() const { return type_; }
  84
  85   // Returns true if the current object represents a given type.
  86   bool IsType(Type type) const { return type == type_; }
  87
  88   // These methods allow the convenient retrieval of the contents of the Value.
  89   // If the current object can be converted into the given type, the value is
  90   // returned through the |out_value| parameter and true is returned;
  91   // otherwise, false is returned and |out_value| is unchanged.
  92   virtual bool GetAsBoolean(bool* out_value) const;
  93   virtual bool GetAsInteger(int* out_value) const;
  94   virtual bool GetAsDouble(double* out_value) const;
  95   virtual bool GetAsString(std::string* out_value) const;
  96   virtual bool GetAsString(string16* out_value) const;
  97   virtual bool GetAsList(ListValue** out_value);
  98   virtual bool GetAsList(const ListValue** out_value) const;
  99   virtual bool GetAsDictionary(DictionaryValue** out_value);
 100   virtual bool GetAsDictionary(const DictionaryValue** out_value) const;
 101   // Note: Do not add more types. See the file-level comment above for why.
 102
 103   // This creates a deep copy of the entire Value tree, and returns a pointer
 104   // to the copy.  The caller gets ownership of the copy, of course.
 105   //
 106   // Subclasses return their own type directly in their overrides;
 107   // this works because C++ supports covariant return types.
 108   virtual Value* DeepCopy() const;
 109
 110   // Compares if two Value objects have equal contents.
 111   virtual bool Equals(const Value* other) const;
 112
 113   // Compares if two Value objects have equal contents. Can handle NULLs.
 114   // NULLs are considered equal but different from Value::CreateNullValue().
 115   static bool Equals(const Value* a, const Value* b);
 116
 117  protected:
 118   // These aren't safe for end-users, but they are useful for subclasses.
 119   explicit Value(Type type);
 120   Value(const Value& that);
 121   Value& operator=(const Value& that);
 122
 123  private:
 124   Type type_;
 125 };
 126
 127 // FundamentalValue represents the simple fundamental types of values.
 128 class BASE_EXPORT FundamentalValue : public Value {
 129  public:
 130   explicit FundamentalValue(bool in_value);
 131   explicit FundamentalValue(int in_value);
 132   explicit FundamentalValue(double in_value);
 133   virtual ~FundamentalValue();
 134
 135   // Overridden from Value:
 136   virtual bool GetAsBoolean(bool* out_value) const OVERRIDE;
 137   virtual bool GetAsInteger(int* out_value) const OVERRIDE;
 138   virtual bool GetAsDouble(double* out_value) const OVERRIDE;
 139   virtual FundamentalValue* DeepCopy() const OVERRIDE;
 140   virtual bool Equals(const Value* other) const OVERRIDE;
 141
 142  private:
 143   union {
 144     bool boolean_value_;
 145     int integer_value_;
 146     double double_value_;
 147   };
 148 };
 149
 150 class BASE_EXPORT StringValue : public Value {
 151  public:
 152   // Initializes a StringValue with a UTF-8 narrow character string.
 153   explicit StringValue(const std::string& in_value);
 154
 155   // Initializes a StringValue with a string16.
 156   explicit StringValue(const string16& in_value);
 157
 158   virtual ~StringValue();
 159
 160   // Overridden from Value:
 161   virtual bool GetAsString(std::string* out_value) const OVERRIDE;
 162   virtual bool GetAsString(string16* out_value) const OVERRIDE;
 163   virtual StringValue* DeepCopy() const OVERRIDE;
 164   virtual bool Equals(const Value* other) const OVERRIDE;
 165
 166  private:
 167   std::string value_;
 168 };
 169
 170 class BASE_EXPORT BinaryValue: public Value {
 171  public:
 172   // Creates a BinaryValue with a null buffer and size of 0.
 173   BinaryValue();
 174
 175   // Creates a BinaryValue, taking ownership of the bytes pointed to by
 176   // |buffer|.
 177   BinaryValue(scoped_ptr<char[]> buffer, size_t size);
 178
 179   virtual ~BinaryValue();
 180
 181   // For situations where you want to keep ownership of your buffer, this
 182   // factory method creates a new BinaryValue by copying the contents of the
 183   // buffer that's passed in.
 184   static BinaryValue* CreateWithCopiedBuffer(const char* buffer, size_t size);
 185
 186   size_t GetSize() const { return size_; }
 187
 188   // May return NULL.
 189   char* GetBuffer() { return buffer_.get(); }
 190   const char* GetBuffer() const { return buffer_.get(); }
 191
 192   // Overridden from Value:
 193   virtual BinaryValue* DeepCopy() const OVERRIDE;
 194   virtual bool Equals(const Value* other) const OVERRIDE;
 195
 196  private:
 197   scoped_ptr<char[]> buffer_;
 198   size_t size_;
 199
 200   DISALLOW_COPY_AND_ASSIGN(BinaryValue);
 201 };
 202
 203 // DictionaryValue provides a key-value dictionary with (optional) "path"
 204 // parsing for recursive access; see the comment at the top of the file. Keys
 205 // are |std::string|s and should be UTF-8 encoded.
 206 class BASE_EXPORT DictionaryValue : public Value {
 207  public:
 208   DictionaryValue();
 209   virtual ~DictionaryValue();
 210
 211   // Overridden from Value:
 212   virtual bool GetAsDictionary(DictionaryValue** out_value) OVERRIDE;
 213   virtual bool GetAsDictionary(
 214       const DictionaryValue** out_value) const OVERRIDE;
 215
 216   // Returns true if the current dictionary has a value for the given key.
 217   bool HasKey(const std::string& key) const;
 218
 219   // Returns the number of Values in this dictionary.
 220   size_t size() const { return dictionary_.size(); }
 221
 222   // Returns whether the dictionary is empty.
 223   bool empty() const { return dictionary_.empty(); }
 224
 225   // Clears any current contents of this dictionary.
 226   void Clear();
 227
 228   // Sets the Value associated with the given path starting from this object.
 229   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
 230   // into the next DictionaryValue down.  Obviously, "." can't be used
 231   // within a key, but there are no other restrictions on keys.
 232   // If the key at any step of the way doesn't exist, or exists but isn't
 233   // a DictionaryValue, a new DictionaryValue will be created and attached
 234   // to the path in that location.
 235   // Note that the dictionary takes ownership of the value referenced by
 236   // |in_value|, and therefore |in_value| must be non-NULL.
 237   void Set(const std::string& path, Value* in_value);
 238
 239   // Convenience forms of Set().  These methods will replace any existing
 240   // value at that path, even if it has a different type.
 241   void SetBoolean(const std::string& path, bool in_value);
 242   void SetInteger(const std::string& path, int in_value);
 243   void SetDouble(const std::string& path, double in_value);
 244   void SetString(const std::string& path, const std::string& in_value);
 245   void SetString(const std::string& path, const string16& in_value);
 246
 247   // Like Set(), but without special treatment of '.'.  This allows e.g. URLs to
 248   // be used as paths.
 249   void SetWithoutPathExpansion(const std::string& key, Value* in_value);
 250
 251   // Convenience forms of SetWithoutPathExpansion().
 252   void SetBooleanWithoutPathExpansion(const std::string& path, bool in_value);
 253   void SetIntegerWithoutPathExpansion(const std::string& path, int in_value);
 254   void SetDoubleWithoutPathExpansion(const std::string& path, double in_value);
 255   void SetStringWithoutPathExpansion(const std::string& path,
 256                                      const std::string& in_value);
 257   void SetStringWithoutPathExpansion(const std::string& path,
 258                                      const string16& in_value);
 259
 260   // Gets the Value associated with the given path starting from this object.
 261   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
 262   // into the next DictionaryValue down.  If the path can be resolved
 263   // successfully, the value for the last key in the path will be returned
 264   // through the |out_value| parameter, and the function will return true.
 265   // Otherwise, it will return false and |out_value| will be untouched.
 266   // Note that the dictionary always owns the value that's returned.
 267   bool Get(const std::string& path, const Value** out_value) const;
 268   bool Get(const std::string& path, Value** out_value);
 269
 270   // These are convenience forms of Get().  The value will be retrieved
 271   // and the return value will be true if the path is valid and the value at
 272   // the end of the path can be returned in the form specified.
 273   bool GetBoolean(const std::string& path, bool* out_value) const;
 274   bool GetInteger(const std::string& path, int* out_value) const;
 275   bool GetDouble(const std::string& path, double* out_value) const;
 276   bool GetString(const std::string& path, std::string* out_value) const;
 277   bool GetString(const std::string& path, string16* out_value) const;
 278   bool GetStringASCII(const std::string& path, std::string* out_value) const;
 279   bool GetBinary(const std::string& path, const BinaryValue** out_value) const;
 280   bool GetBinary(const std::string& path, BinaryValue** out_value);
 281   bool GetDictionary(const std::string& path,
 282                      const DictionaryValue** out_value) const;
 283   bool GetDictionary(const std::string& path, DictionaryValue** out_value);
 284   bool GetList(const std::string& path, const ListValue** out_value) const;
 285   bool GetList(const std::string& path, ListValue** out_value);
 286
 287   // Like Get(), but without special treatment of '.'.  This allows e.g. URLs to
 288   // be used as paths.
 289   bool GetWithoutPathExpansion(const std::string& key,
 290                                const Value** out_value) const;
 291   bool GetWithoutPathExpansion(const std::string& key, Value** out_value);
 292   bool GetBooleanWithoutPathExpansion(const std::string& key,
 293                                       bool* out_value) const;
 294   bool GetIntegerWithoutPathExpansion(const std::string& key,
 295                                       int* out_value) const;
 296   bool GetDoubleWithoutPathExpansion(const std::string& key,
 297                                      double* out_value) const;
 298   bool GetStringWithoutPathExpansion(const std::string& key,
 299                                      std::string* out_value) const;
 300   bool GetStringWithoutPathExpansion(const std::string& key,
 301                                      string16* out_value) const;
 302   bool GetDictionaryWithoutPathExpansion(
 303       const std::string& key,
 304       const DictionaryValue** out_value) const;
 305   bool GetDictionaryWithoutPathExpansion(const std::string& key,
 306                                          DictionaryValue** out_value);
 307   bool GetListWithoutPathExpansion(const std::string& key,
 308                                    const ListValue** out_value) const;
 309   bool GetListWithoutPathExpansion(const std::string& key,
 310                                    ListValue** out_value);
 311
 312   // Removes the Value with the specified path from this dictionary (or one
 313   // of its child dictionaries, if the path is more than just a local key).
 314   // If |out_value| is non-NULL, the removed Value will be passed out via
 315   // |out_value|.  If |out_value| is NULL, the removed value will be deleted.
 316   // This method returns true if |path| is a valid path; otherwise it will
 317   // return false and the DictionaryValue object will be unchanged.
 318   virtual bool Remove(const std::string& path, scoped_ptr<Value>* out_value);
 319
 320   // Like Remove(), but without special treatment of '.'.  This allows e.g. URLs
 321   // to be used as paths.
 322   virtual bool RemoveWithoutPathExpansion(const std::string& key,
 323                                           scoped_ptr<Value>* out_value);
 324
 325   // Makes a copy of |this| but doesn't include empty dictionaries and lists in
 326   // the copy.  This never returns NULL, even if |this| itself is empty.
 327   DictionaryValue* DeepCopyWithoutEmptyChildren();
 328
 329   // Merge |dictionary| into this dictionary. This is done recursively, i.e. any
 330   // sub-dictionaries will be merged as well. In case of key collisions, the
 331   // passed in dictionary takes precedence and data already present will be
 332   // replaced. Values within |dictionary| are deep-copied, so |dictionary| may
 333   // be freed any time after this call.
 334   void MergeDictionary(const DictionaryValue* dictionary);
 335
 336   // Swaps contents with the |other| dictionary.
 337   virtual void Swap(DictionaryValue* other);
 338
 339   // This class provides an iterator over both keys and values in the
 340   // dictionary.  It can't be used to modify the dictionary.
 341   class BASE_EXPORT Iterator {
 342    public:
 343     explicit Iterator(const DictionaryValue& target);
 344
 345     bool IsAtEnd() const { return it_ == target_.dictionary_.end(); }
 346     void Advance() { ++it_; }
 347
 348     const std::string& key() const { return it_->first; }
 349     const Value& value() const { return *it_->second; }
 350
 351    private:
 352     const DictionaryValue& target_;
 353     ValueMap::const_iterator it_;
 354   };
 355
 356   // Overridden from Value:
 357   virtual DictionaryValue* DeepCopy() const OVERRIDE;
 358   virtual bool Equals(const Value* other) const OVERRIDE;
 359
 360  private:
 361   ValueMap dictionary_;
 362
 363   DISALLOW_COPY_AND_ASSIGN(DictionaryValue);
 364 };
 365
 366 // This type of Value represents a list of other Value values.
 367 class BASE_EXPORT ListValue : public Value {
 368  public:
 369   typedef ValueVector::iterator iterator;
 370   typedef ValueVector::const_iterator const_iterator;
 371
 372   ListValue();
 373   virtual ~ListValue();
 374
 375   // Clears the contents of this ListValue
 376   void Clear();
 377
 378   // Returns the number of Values in this list.
 379   size_t GetSize() const { return list_.size(); }
 380
 381   // Returns whether the list is empty.
 382   bool empty() const { return list_.empty(); }
 383
 384   // Sets the list item at the given index to be the Value specified by
 385   // the value given.  If the index beyond the current end of the list, null
 386   // Values will be used to pad out the list.
 387   // Returns true if successful, or false if the index was negative or
 388   // the value is a null pointer.
 389   bool Set(size_t index, Value* in_value);
 390
 391   // Gets the Value at the given index.  Modifies |out_value| (and returns true)
 392   // only if the index falls within the current list range.
 393   // Note that the list always owns the Value passed out via |out_value|.
 394   bool Get(size_t index, const Value** out_value) const;
 395   bool Get(size_t index, Value** out_value);
 396
 397   // Convenience forms of Get().  Modifies |out_value| (and returns true)
 398   // only if the index is valid and the Value at that index can be returned
 399   // in the specified form.
 400   bool GetBoolean(size_t index, bool* out_value) const;
 401   bool GetInteger(size_t index, int* out_value) const;
 402   bool GetDouble(size_t index, double* out_value) const;
 403   bool GetString(size_t index, std::string* out_value) const;
 404   bool GetString(size_t index, string16* out_value) const;
 405   bool GetBinary(size_t index, const BinaryValue** out_value) const;
 406   bool GetBinary(size_t index, BinaryValue** out_value);
 407   bool GetDictionary(size_t index, const DictionaryValue** out_value) const;
 408   bool GetDictionary(size_t index, DictionaryValue** out_value);
 409   bool GetList(size_t index, const ListValue** out_value) const;
 410   bool GetList(size_t index, ListValue** out_value);
 411
 412   // Removes the Value with the specified index from this list.
 413   // If |out_value| is non-NULL, the removed Value AND ITS OWNERSHIP will be
 414   // passed out via |out_value|.  If |out_value| is NULL, the removed value will
 415   // be deleted.  This method returns true if |index| is valid; otherwise
 416   // it will return false and the ListValue object will be unchanged.
 417   virtual bool Remove(size_t index, scoped_ptr<Value>* out_value);
 418
 419   // Removes the first instance of |value| found in the list, if any, and
 420   // deletes it. |index| is the location where |value| was found. Returns false
 421   // if not found.
 422   bool Remove(const Value& value, size_t* index);
 423
 424   // Removes the element at |iter|. If |out_value| is NULL, the value will be
 425   // deleted, otherwise ownership of the value is passed back to the caller.
 426   // Returns an iterator pointing to the location of the element that
 427   // followed the erased element.
 428   iterator Erase(iterator iter, scoped_ptr<Value>* out_value);
 429
 430   // Appends a Value to the end of the list.
 431   void Append(Value* in_value);
 432
 433   // Convenience forms of Append.
 434   void AppendBoolean(bool in_value);
 435   void AppendInteger(int in_value);
 436   void AppendDouble(double in_value);
 437   void AppendString(const std::string& in_value);
 438   void AppendString(const string16& in_value);
 439   void AppendStrings(const std::vector<std::string>& in_values);
 440   void AppendStrings(const std::vector<string16>& in_values);
 441
 442   // Appends a Value if it's not already present. Takes ownership of the
 443   // |in_value|. Returns true if successful, or false if the value was already
 444   // present. If the value was already present the |in_value| is deleted.
 445   bool AppendIfNotPresent(Value* in_value);
 446
 447   // Insert a Value at index.
 448   // Returns true if successful, or false if the index was out of range.
 449   bool Insert(size_t index, Value* in_value);
 450
 451   // Searches for the first instance of |value| in the list using the Equals
 452   // method of the Value type.
 453   // Returns a const_iterator to the found item or to end() if none exists.
 454   const_iterator Find(const Value& value) const;
 455
 456   // Swaps contents with the |other| list.
 457   virtual void Swap(ListValue* other);
 458
 459   // Iteration.
 460   iterator begin() { return list_.begin(); }
 461   iterator end() { return list_.end(); }
 462
 463   const_iterator begin() const { return list_.begin(); }
 464   const_iterator end() const { return list_.end(); }
 465
 466   // Overridden from Value:
 467   virtual bool GetAsList(ListValue** out_value) OVERRIDE;
 468   virtual bool GetAsList(const ListValue** out_value) const OVERRIDE;
 469   virtual ListValue* DeepCopy() const OVERRIDE;
 470   virtual bool Equals(const Value* other) const OVERRIDE;
 471
 472  private:
 473   ValueVector list_;
 474
 475   DISALLOW_COPY_AND_ASSIGN(ListValue);
 476 };
 477
 478 // This interface is implemented by classes that know how to serialize and
 479 // deserialize Value objects.
 480 class BASE_EXPORT ValueSerializer {
 481  public:
 482   virtual ~ValueSerializer();
 483
 484   virtual bool Serialize(const Value& root) = 0;
 485
 486   // This method deserializes the subclass-specific format into a Value object.
 487   // If the return value is non-NULL, the caller takes ownership of returned
 488   // Value. If the return value is NULL, and if error_code is non-NULL,
 489   // error_code will be set with the underlying error.
 490   // If |error_message| is non-null, it will be filled in with a formatted
 491   // error message including the location of the error if appropriate.
 492   virtual Value* Deserialize(int* error_code, std::string* error_str) = 0;
 493 };
 494
 495 // Stream operator so Values can be used in assertion statements.  In order that
 496 // gtest uses this operator to print readable output on test failures, we must
 497 // override each specific type. Otherwise, the default template implementation
 498 // is preferred over an upcast.
 499 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const Value& value);
 500
 501 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 502                                             const FundamentalValue& value) {
 503   return out << static_cast<const Value&>(value);
 504 }
 505
 506 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 507                                             const StringValue& value) {
 508   return out << static_cast<const Value&>(value);
 509 }
 510
 511 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 512                                             const DictionaryValue& value) {
 513   return out << static_cast<const Value&>(value);
 514 }
 515
 516 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 517                                             const ListValue& value) {
 518   return out << static_cast<const Value&>(value);
 519 }
 520
 521 }  // namespace base
 522
 523 // http://crbug.com/88666
 524 using base::DictionaryValue;
 525 using base::ListValue;
 526 using base::StringValue;
 527 using base::Value;
 528
 529 #endif  // BASE_VALUES_H_