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 <stddef.h>
  21
  22 #include <iosfwd>
  23 #include <map>
  24 #include <string>
  25 #include <utility>
  26 #include <vector>
  27
  28 #include "base/base_export.h"
  29 #include "base/basictypes.h"
  30 #include "base/compiler_specific.h"
  31 #include "base/memory/scoped_ptr.h"
  32 #include "base/strings/string16.h"
  33
  34 namespace base {
  35
  36 class DictionaryValue;
  37 class FundamentalValue;
  38 class ListValue;
  39 class StringValue;
  40 class Value;
  41
  42 typedef std::vector<Value*> ValueVector;
  43 typedef std::map<std::string, Value*> ValueMap;
  44
  45 // The Value class is the base class for Values. A Value can be instantiated
  46 // via the Create*Value() factory methods, or by directly creating instances of
  47 // the subclasses.
  48 //
  49 // See the file-level comment above for more information.
  50 class BASE_EXPORT Value {
  51  public:
  52   enum Type {
  53     TYPE_NULL = 0,
  54     TYPE_BOOLEAN,
  55     TYPE_INTEGER,
  56     TYPE_DOUBLE,
  57     TYPE_STRING,
  58     TYPE_BINARY,
  59     TYPE_DICTIONARY,
  60     TYPE_LIST
  61     // Note: Do not add more types. See the file-level comment above for why.
  62   };
  63
  64   virtual ~Value();
  65
  66   static Value* CreateNullValue();
  67
  68   // Returns the type of the value stored by the current Value object.
  69   // Each type will be implemented by only one subclass of Value, so it's
  70   // safe to use the Type to determine whether you can cast from
  71   // Value* to (Implementing Class)*.  Also, a Value object never changes
  72   // its type after construction.
  73   Type GetType() const { return type_; }
  74
  75   // Returns true if the current object represents a given type.
  76   bool IsType(Type type) const { return type == type_; }
  77
  78   // These methods allow the convenient retrieval of the contents of the Value.
  79   // If the current object can be converted into the given type, the value is
  80   // returned through the |out_value| parameter and true is returned;
  81   // otherwise, false is returned and |out_value| is unchanged.
  82   virtual bool GetAsBoolean(bool* out_value) const;
  83   virtual bool GetAsInteger(int* out_value) const;
  84   virtual bool GetAsDouble(double* out_value) const;
  85   virtual bool GetAsString(std::string* out_value) const;
  86   virtual bool GetAsString(string16* out_value) const;
  87   virtual bool GetAsString(const StringValue** out_value) const;
  88   virtual bool GetAsList(ListValue** out_value);
  89   virtual bool GetAsList(const ListValue** out_value) const;
  90   virtual bool GetAsDictionary(DictionaryValue** out_value);
  91   virtual bool GetAsDictionary(const DictionaryValue** out_value) const;
  92   // Note: Do not add more types. See the file-level comment above for why.
  93
  94   // This creates a deep copy of the entire Value tree, and returns a pointer
  95   // to the copy.  The caller gets ownership of the copy, of course.
  96   //
  97   // Subclasses return their own type directly in their overrides;
  98   // this works because C++ supports covariant return types.
  99   virtual Value* DeepCopy() const;
 100
 101   // Compares if two Value objects have equal contents.
 102   virtual bool Equals(const Value* other) const;
 103
 104   // Compares if two Value objects have equal contents. Can handle NULLs.
 105   // NULLs are considered equal but different from Value::CreateNullValue().
 106   static bool Equals(const Value* a, const Value* b);
 107
 108  protected:
 109   // These aren't safe for end-users, but they are useful for subclasses.
 110   explicit Value(Type type);
 111   Value(const Value& that);
 112   Value& operator=(const Value& that);
 113
 114  private:
 115   Type type_;
 116 };
 117
 118 // FundamentalValue represents the simple fundamental types of values.
 119 class BASE_EXPORT FundamentalValue : public Value {
 120  public:
 121   explicit FundamentalValue(bool in_value);
 122   explicit FundamentalValue(int in_value);
 123   explicit FundamentalValue(double in_value);
 124   ~FundamentalValue() override;
 125
 126   // Overridden from Value:
 127   bool GetAsBoolean(bool* out_value) const override;
 128   bool GetAsInteger(int* out_value) const override;
 129   // Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
 130   // doubles.
 131   bool GetAsDouble(double* out_value) const override;
 132   FundamentalValue* DeepCopy() const override;
 133   bool Equals(const Value* other) const override;
 134
 135  private:
 136   union {
 137     bool boolean_value_;
 138     int integer_value_;
 139     double double_value_;
 140   };
 141 };
 142
 143 class BASE_EXPORT StringValue : public Value {
 144  public:
 145   // Initializes a StringValue with a UTF-8 narrow character string.
 146   explicit StringValue(const std::string& in_value);
 147
 148   // Initializes a StringValue with a string16.
 149   explicit StringValue(const string16& in_value);
 150
 151   ~StringValue() override;
 152
 153   // Returns |value_| as a pointer or reference.
 154   std::string* GetString();
 155   const std::string& GetString() const;
 156
 157   // Overridden from Value:
 158   bool GetAsString(std::string* out_value) const override;
 159   bool GetAsString(string16* out_value) const override;
 160   bool GetAsString(const StringValue** out_value) const override;
 161   StringValue* DeepCopy() const override;
 162   bool Equals(const Value* other) const override;
 163
 164  private:
 165   std::string value_;
 166 };
 167
 168 class BASE_EXPORT BinaryValue: public Value {
 169  public:
 170   // Creates a BinaryValue with a null buffer and size of 0.
 171   BinaryValue();
 172
 173   // Creates a BinaryValue, taking ownership of the bytes pointed to by
 174   // |buffer|.
 175   BinaryValue(scoped_ptr<char[]> buffer, size_t size);
 176
 177   ~BinaryValue() override;
 178
 179   // For situations where you want to keep ownership of your buffer, this
 180   // factory method creates a new BinaryValue by copying the contents of the
 181   // buffer that's passed in.
 182   static BinaryValue* CreateWithCopiedBuffer(const char* buffer, size_t size);
 183
 184   size_t GetSize() const { return size_; }
 185
 186   // May return NULL.
 187   char* GetBuffer() { return buffer_.get(); }
 188   const char* GetBuffer() const { return buffer_.get(); }
 189
 190   // Overridden from Value:
 191   BinaryValue* DeepCopy() const override;
 192   bool Equals(const Value* other) const override;
 193
 194  private:
 195   scoped_ptr<char[]> buffer_;
 196   size_t size_;
 197
 198   DISALLOW_COPY_AND_ASSIGN(BinaryValue);
 199 };
 200
 201 // DictionaryValue provides a key-value dictionary with (optional) "path"
 202 // parsing for recursive access; see the comment at the top of the file. Keys
 203 // are |std::string|s and should be UTF-8 encoded.
 204 class BASE_EXPORT DictionaryValue : public Value {
 205  public:
 206   DictionaryValue();
 207   ~DictionaryValue() override;
 208
 209   // Overridden from Value:
 210   bool GetAsDictionary(DictionaryValue** out_value) override;
 211   bool GetAsDictionary(const DictionaryValue** out_value) const override;
 212
 213   // Returns true if the current dictionary has a value for the given key.
 214   bool HasKey(const std::string& key) const;
 215
 216   // Returns the number of Values in this dictionary.
 217   size_t size() const { return dictionary_.size(); }
 218
 219   // Returns whether the dictionary is empty.
 220   bool empty() const { return dictionary_.empty(); }
 221
 222   // Clears any current contents of this dictionary.
 223   void Clear();
 224
 225   // Sets the Value associated with the given path starting from this object.
 226   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
 227   // into the next DictionaryValue down.  Obviously, "." can't be used
 228   // within a key, but there are no other restrictions on keys.
 229   // If the key at any step of the way doesn't exist, or exists but isn't
 230   // a DictionaryValue, a new DictionaryValue will be created and attached
 231   // to the path in that location.
 232   // Note that the dictionary takes ownership of the value referenced by
 233   // |in_value|, and therefore |in_value| must be non-NULL.
 234   void Set(const std::string& path, Value* in_value);
 235
 236   // Convenience forms of Set().  These methods will replace any existing
 237   // value at that path, even if it has a different type.
 238   void SetBoolean(const std::string& path, bool in_value);
 239   void SetInteger(const std::string& path, int in_value);
 240   void SetDouble(const std::string& path, double in_value);
 241   void SetString(const std::string& path, const std::string& in_value);
 242   void SetString(const std::string& path, const string16& in_value);
 243
 244   // Like Set(), but without special treatment of '.'.  This allows e.g. URLs to
 245   // be used as paths.
 246   void SetWithoutPathExpansion(const std::string& key, Value* in_value);
 247
 248   // Convenience forms of SetWithoutPathExpansion().
 249   void SetBooleanWithoutPathExpansion(const std::string& path, bool in_value);
 250   void SetIntegerWithoutPathExpansion(const std::string& path, int in_value);
 251   void SetDoubleWithoutPathExpansion(const std::string& path, double in_value);
 252   void SetStringWithoutPathExpansion(const std::string& path,
 253                                      const std::string& in_value);
 254   void SetStringWithoutPathExpansion(const std::string& path,
 255                                      const string16& in_value);
 256
 257   // Gets the Value associated with the given path starting from this object.
 258   // A path has the form "<key>" or "<key>.<key>.[...]", where "." indexes
 259   // into the next DictionaryValue down.  If the path can be resolved
 260   // successfully, the value for the last key in the path will be returned
 261   // through the |out_value| parameter, and the function will return true.
 262   // Otherwise, it will return false and |out_value| will be untouched.
 263   // Note that the dictionary always owns the value that's returned.
 264   // |out_value| is optional and will only be set if non-NULL.
 265   bool Get(const std::string& path, const Value** out_value) const;
 266   bool Get(const std::string& path, Value** out_value);
 267
 268   // These are convenience forms of Get().  The value will be retrieved
 269   // and the return value will be true if the path is valid and the value at
 270   // the end of the path can be returned in the form specified.
 271   // |out_value| is optional and will only be set if non-NULL.
 272   bool GetBoolean(const std::string& path, bool* out_value) const;
 273   bool GetInteger(const std::string& path, int* out_value) const;
 274   // Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
 275   // doubles.
 276   bool GetDouble(const std::string& path, double* out_value) const;
 277   bool GetString(const std::string& path, std::string* out_value) const;
 278   bool GetString(const std::string& path, string16* out_value) const;
 279   bool GetStringASCII(const std::string& path, std::string* out_value) const;
 280   bool GetBinary(const std::string& path, const BinaryValue** out_value) const;
 281   bool GetBinary(const std::string& path, BinaryValue** out_value);
 282   bool GetDictionary(const std::string& path,
 283                      const DictionaryValue** out_value) const;
 284   bool GetDictionary(const std::string& path, DictionaryValue** out_value);
 285   bool GetList(const std::string& path, const ListValue** out_value) const;
 286   bool GetList(const std::string& path, ListValue** out_value);
 287
 288   // Like Get(), but without special treatment of '.'.  This allows e.g. URLs to
 289   // be used as paths.
 290   bool GetWithoutPathExpansion(const std::string& key,
 291                                const Value** out_value) const;
 292   bool GetWithoutPathExpansion(const std::string& key, Value** out_value);
 293   bool GetBooleanWithoutPathExpansion(const std::string& key,
 294                                       bool* out_value) const;
 295   bool GetIntegerWithoutPathExpansion(const std::string& key,
 296                                       int* out_value) const;
 297   bool GetDoubleWithoutPathExpansion(const std::string& key,
 298                                      double* out_value) const;
 299   bool GetStringWithoutPathExpansion(const std::string& key,
 300                                      std::string* out_value) const;
 301   bool GetStringWithoutPathExpansion(const std::string& key,
 302                                      string16* out_value) const;
 303   bool GetDictionaryWithoutPathExpansion(
 304       const std::string& key,
 305       const DictionaryValue** out_value) const;
 306   bool GetDictionaryWithoutPathExpansion(const std::string& key,
 307                                          DictionaryValue** out_value);
 308   bool GetListWithoutPathExpansion(const std::string& key,
 309                                    const ListValue** out_value) const;
 310   bool GetListWithoutPathExpansion(const std::string& key,
 311                                    ListValue** out_value);
 312
 313   // Removes the Value with the specified path from this dictionary (or one
 314   // of its child dictionaries, if the path is more than just a local key).
 315   // If |out_value| is non-NULL, the removed Value will be passed out via
 316   // |out_value|.  If |out_value| is NULL, the removed value will be deleted.
 317   // This method returns true if |path| is a valid path; otherwise it will
 318   // return false and the DictionaryValue object will be unchanged.
 319   virtual bool Remove(const std::string& path, scoped_ptr<Value>* out_value);
 320
 321   // Like Remove(), but without special treatment of '.'.  This allows e.g. URLs
 322   // to be used as paths.
 323   virtual bool RemoveWithoutPathExpansion(const std::string& key,
 324                                           scoped_ptr<Value>* out_value);
 325
 326   // Removes a path, clearing out all dictionaries on |path| that remain empty
 327   // after removing the value at |path|.
 328   virtual bool RemovePath(const std::string& path,
 329                           scoped_ptr<Value>* out_value);
 330
 331   // Makes a copy of |this| but doesn't include empty dictionaries and lists in
 332   // the copy.  This never returns NULL, even if |this| itself is empty.
 333   DictionaryValue* DeepCopyWithoutEmptyChildren() const;
 334
 335   // Merge |dictionary| into this dictionary. This is done recursively, i.e. any
 336   // sub-dictionaries will be merged as well. In case of key collisions, the
 337   // passed in dictionary takes precedence and data already present will be
 338   // replaced. Values within |dictionary| are deep-copied, so |dictionary| may
 339   // be freed any time after this call.
 340   void MergeDictionary(const DictionaryValue* dictionary);
 341
 342   // Swaps contents with the |other| dictionary.
 343   virtual void Swap(DictionaryValue* other);
 344
 345   // This class provides an iterator over both keys and values in the
 346   // dictionary.  It can't be used to modify the dictionary.
 347   class BASE_EXPORT Iterator {
 348    public:
 349     explicit Iterator(const DictionaryValue& target);
 350     ~Iterator();
 351
 352     bool IsAtEnd() const { return it_ == target_.dictionary_.end(); }
 353     void Advance() { ++it_; }
 354
 355     const std::string& key() const { return it_->first; }
 356     const Value& value() const { return *it_->second; }
 357
 358    private:
 359     const DictionaryValue& target_;
 360     ValueMap::const_iterator it_;
 361   };
 362
 363   // Overridden from Value:
 364   DictionaryValue* DeepCopy() const override;
 365   bool Equals(const Value* other) const override;
 366
 367  private:
 368   ValueMap dictionary_;
 369
 370   DISALLOW_COPY_AND_ASSIGN(DictionaryValue);
 371 };
 372
 373 // This type of Value represents a list of other Value values.
 374 class BASE_EXPORT ListValue : public Value {
 375  public:
 376   typedef ValueVector::iterator iterator;
 377   typedef ValueVector::const_iterator const_iterator;
 378
 379   ListValue();
 380   ~ListValue() override;
 381
 382   // Clears the contents of this ListValue
 383   void Clear();
 384
 385   // Returns the number of Values in this list.
 386   size_t GetSize() const { return list_.size(); }
 387
 388   // Returns whether the list is empty.
 389   bool empty() const { return list_.empty(); }
 390
 391   // Sets the list item at the given index to be the Value specified by
 392   // the value given.  If the index beyond the current end of the list, null
 393   // Values will be used to pad out the list.
 394   // Returns true if successful, or false if the index was negative or
 395   // the value is a null pointer.
 396   bool Set(size_t index, Value* in_value);
 397
 398   // Gets the Value at the given index.  Modifies |out_value| (and returns true)
 399   // only if the index falls within the current list range.
 400   // Note that the list always owns the Value passed out via |out_value|.
 401   // |out_value| is optional and will only be set if non-NULL.
 402   bool Get(size_t index, const Value** out_value) const;
 403   bool Get(size_t index, Value** out_value);
 404
 405   // Convenience forms of Get().  Modifies |out_value| (and returns true)
 406   // only if the index is valid and the Value at that index can be returned
 407   // in the specified form.
 408   // |out_value| is optional and will only be set if non-NULL.
 409   bool GetBoolean(size_t index, bool* out_value) const;
 410   bool GetInteger(size_t index, int* out_value) const;
 411   // Values of both type TYPE_INTEGER and TYPE_DOUBLE can be obtained as
 412   // doubles.
 413   bool GetDouble(size_t index, double* out_value) const;
 414   bool GetString(size_t index, std::string* out_value) const;
 415   bool GetString(size_t index, string16* out_value) const;
 416   bool GetBinary(size_t index, const BinaryValue** out_value) const;
 417   bool GetBinary(size_t index, BinaryValue** out_value);
 418   bool GetDictionary(size_t index, const DictionaryValue** out_value) const;
 419   bool GetDictionary(size_t index, DictionaryValue** out_value);
 420   bool GetList(size_t index, const ListValue** out_value) const;
 421   bool GetList(size_t index, ListValue** out_value);
 422
 423   // Removes the Value with the specified index from this list.
 424   // If |out_value| is non-NULL, the removed Value AND ITS OWNERSHIP will be
 425   // passed out via |out_value|.  If |out_value| is NULL, the removed value will
 426   // be deleted.  This method returns true if |index| is valid; otherwise
 427   // it will return false and the ListValue object will be unchanged.
 428   virtual bool Remove(size_t index, scoped_ptr<Value>* out_value);
 429
 430   // Removes the first instance of |value| found in the list, if any, and
 431   // deletes it. |index| is the location where |value| was found. Returns false
 432   // if not found.
 433   bool Remove(const Value& value, size_t* index);
 434
 435   // Removes the element at |iter|. If |out_value| is NULL, the value will be
 436   // deleted, otherwise ownership of the value is passed back to the caller.
 437   // Returns an iterator pointing to the location of the element that
 438   // followed the erased element.
 439   iterator Erase(iterator iter, scoped_ptr<Value>* out_value);
 440
 441   // Appends a Value to the end of the list.
 442   void Append(Value* in_value);
 443
 444   // Convenience forms of Append.
 445   void AppendBoolean(bool in_value);
 446   void AppendInteger(int in_value);
 447   void AppendDouble(double in_value);
 448   void AppendString(const std::string& in_value);
 449   void AppendString(const string16& in_value);
 450   void AppendStrings(const std::vector<std::string>& in_values);
 451   void AppendStrings(const std::vector<string16>& in_values);
 452
 453   // Appends a Value if it's not already present. Takes ownership of the
 454   // |in_value|. Returns true if successful, or false if the value was already
 455   // present. If the value was already present the |in_value| is deleted.
 456   bool AppendIfNotPresent(Value* in_value);
 457
 458   // Insert a Value at index.
 459   // Returns true if successful, or false if the index was out of range.
 460   bool Insert(size_t index, Value* in_value);
 461
 462   // Searches for the first instance of |value| in the list using the Equals
 463   // method of the Value type.
 464   // Returns a const_iterator to the found item or to end() if none exists.
 465   const_iterator Find(const Value& value) const;
 466
 467   // Swaps contents with the |other| list.
 468   virtual void Swap(ListValue* other);
 469
 470   // Iteration.
 471   iterator begin() { return list_.begin(); }
 472   iterator end() { return list_.end(); }
 473
 474   const_iterator begin() const { return list_.begin(); }
 475   const_iterator end() const { return list_.end(); }
 476
 477   // Overridden from Value:
 478   bool GetAsList(ListValue** out_value) override;
 479   bool GetAsList(const ListValue** out_value) const override;
 480   ListValue* DeepCopy() const override;
 481   bool Equals(const Value* other) const override;
 482
 483  private:
 484   ValueVector list_;
 485
 486   DISALLOW_COPY_AND_ASSIGN(ListValue);
 487 };
 488
 489 // This interface is implemented by classes that know how to serialize and
 490 // deserialize Value objects.
 491 class BASE_EXPORT ValueSerializer {
 492  public:
 493   virtual ~ValueSerializer();
 494
 495   virtual bool Serialize(const Value& root) = 0;
 496
 497   // This method deserializes the subclass-specific format into a Value object.
 498   // If the return value is non-NULL, the caller takes ownership of returned
 499   // Value. If the return value is NULL, and if error_code is non-NULL,
 500   // error_code will be set with the underlying error.
 501   // If |error_message| is non-null, it will be filled in with a formatted
 502   // error message including the location of the error if appropriate.
 503   virtual Value* Deserialize(int* error_code, std::string* error_str) = 0;
 504 };
 505
 506 // Stream operator so Values can be used in assertion statements.  In order that
 507 // gtest uses this operator to print readable output on test failures, we must
 508 // override each specific type. Otherwise, the default template implementation
 509 // is preferred over an upcast.
 510 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const Value& value);
 511
 512 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 513                                             const FundamentalValue& value) {
 514   return out << static_cast<const Value&>(value);
 515 }
 516
 517 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 518                                             const StringValue& value) {
 519   return out << static_cast<const Value&>(value);
 520 }
 521
 522 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 523                                             const DictionaryValue& value) {
 524   return out << static_cast<const Value&>(value);
 525 }
 526
 527 BASE_EXPORT inline std::ostream& operator<<(std::ostream& out,
 528                                             const ListValue& value) {
 529   return out << static_cast<const Value&>(value);
 530 }
 531
 532 }  // namespace base
 533
 534 #endif  // BASE_VALUES_H_