ppapi/cpp/var.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 #ifndef PPAPI_CPP_VAR_H_
   6 #define PPAPI_CPP_VAR_H_
   7
   8 #include <string>
   9 #include <vector>
  10
  11 #include "ppapi/c/pp_var.h"
  12 #include "ppapi/cpp/pass_ref.h"
  13
  14 /// @file
  15 /// This file defines the API for handling the passing of data types between
  16 /// your module and the page.
  17 namespace pp {
  18
  19 /// A generic type used for passing data types between the module and the page.
  20 class Var {
  21  public:
  22   /// Special value passed to constructor to make <code>NULL</code>.
  23   struct Null {};
  24
  25   /// Default constructor. Creates a <code>Var</code> of type
  26   /// <code>Undefined</code>.
  27   Var();
  28
  29   /// A constructor used to create a <code>Var</code> of type <code>Null</code>.
  30   Var(Null);
  31
  32   /// A constructor used to create a <code>Var</code> of type <code>Bool</code>.
  33   ///
  34   /// @param[in] b A boolean value.
  35   Var(bool b);
  36
  37   /// A constructor used to create a 32 bit integer <code>Var</code>.
  38   ///
  39   /// @param[in] i A 32 bit integer value.
  40   Var(int32_t i);
  41
  42   /// A constructor used to create a double value <code>Var</code>.
  43   ///
  44   /// @param[in] d A double value.
  45   Var(double d);
  46
  47   /// A constructor used to create a UTF-8 character <code>Var</code>.
  48   Var(const char* utf8_str);  // Must be encoded in UTF-8.
  49
  50   /// A constructor used to create a UTF-8 character <code>Var</code>.
  51   Var(const std::string& utf8_str);  // Must be encoded in UTF-8.
  52
  53   /// A constructor used when you have received a <code>Var</code> as a return
  54   /// value that has had its reference count incremented for you.
  55   ///
  56   /// You will not normally need to use this constructor because
  57   /// the reference count will not normally be incremented for you.
  58   Var(PassRef, const PP_Var& var) {
  59     var_ = var;
  60     is_managed_ = true;
  61   }
  62
  63   /// A constructor that increments the reference count.
  64   explicit Var(const PP_Var& var);
  65
  66   struct DontManage {};
  67
  68   // TODO(brettw): remove DontManage when this bug is fixed
  69   //               http://code.google.com/p/chromium/issues/detail?id=52105
  70   /// This constructor is used when we've given a <code>PP_Var</code> as an
  71   /// input argument from somewhere and that reference is managing the
  72   /// reference count for us. The object will not have its reference count
  73   /// increased or decreased by this class instance.
  74   ///
  75   /// @param[in] var A <code>Var</code>.
  76   Var(DontManage, const PP_Var& var) {
  77     var_ = var;
  78     is_managed_ = false;
  79   }
  80
  81   /// A constructor for copying a <code>Var</code>.
  82   Var(const Var& other);
  83
  84   /// Destructor.
  85   virtual ~Var();
  86
  87   /// This function assigns one <code>Var</code> to another <code>Var</code>.
  88   ///
  89   /// @param[in] other The <code>Var</code> to be assigned.
  90   ///
  91   /// @return A resulting <code>Var</code>.
  92   virtual Var& operator=(const Var& other);
  93
  94   /// This function compares object identity (rather than value identity) for
  95   /// objects, dictionaries, and arrays
  96   ///
  97   /// @param[in] other The <code>Var</code> to be compared to this Var.
  98   ///
  99   /// @return true if the <code>other</code> <code>Var</code> is the same as
 100   /// this <code>Var</code>, otherwise false.
 101   bool operator==(const Var& other) const;
 102
 103   /// This function determines if this <code>Var</code> is an undefined value.
 104   ///
 105   /// @return true if this <code>Var</code> is undefined, otherwise false.
 106   bool is_undefined() const { return var_.type == PP_VARTYPE_UNDEFINED; }
 107
 108   /// This function determines if this <code>Var</code> is a null value.
 109   ///
 110   /// @return true if this <code>Var</code> is null, otherwise false.
 111   bool is_null() const { return var_.type == PP_VARTYPE_NULL; }
 112
 113   /// This function determines if this <code>Var</code> is a bool value.
 114   ///
 115   /// @return true if this <code>Var</code> is a bool, otherwise false.
 116   bool is_bool() const { return var_.type == PP_VARTYPE_BOOL; }
 117
 118   /// This function determines if this <code>Var</code> is a string value.
 119   ///
 120   /// @return true if this <code>Var</code> is a string, otherwise false.
 121   bool is_string() const { return var_.type == PP_VARTYPE_STRING; }
 122
 123   /// This function determines if this <code>Var</code> is an object.
 124   ///
 125   /// @return true if this <code>Var</code> is an object, otherwise false.
 126   bool is_object() const { return var_.type == PP_VARTYPE_OBJECT; }
 127
 128   /// This function determines if this <code>Var</code> is an array.
 129   ///
 130   /// @return true if this <code>Var</code> is an array, otherwise false.
 131   bool is_array() const { return var_.type == PP_VARTYPE_ARRAY; }
 132
 133   /// This function determines if this <code>Var</code> is a dictionary.
 134   ///
 135   /// @return true if this <code>Var</code> is a dictionary, otherwise false.
 136   bool is_dictionary() const { return var_.type == PP_VARTYPE_DICTIONARY; }
 137
 138   /// This function determines if this <code>Var</code> is an integer value.
 139   /// The <code>is_int</code> function returns the internal representation.
 140   /// The JavaScript runtime may convert between the two as needed, so the
 141   /// distinction may not be relevant in all cases (int is really an
 142   /// optimization inside the runtime). So most of the time, you will want
 143   /// to check is_number().
 144   ///
 145   /// @return true if this <code>Var</code> is an integer, otherwise false.
 146   bool is_int() const { return var_.type == PP_VARTYPE_INT32; }
 147
 148   /// This function determines if this <code>Var</code> is a double value.
 149   /// The <code>is_double</code> function returns the internal representation.
 150   /// The JavaScript runtime may convert between the two as needed, so the
 151   /// distinction may not be relevant in all cases (int is really an
 152   /// optimization inside the runtime). So most of the time, you will want to
 153   /// check is_number().
 154   ///
 155   /// @return true if this <code>Var</code> is a double, otherwise false.
 156   bool is_double() const { return var_.type == PP_VARTYPE_DOUBLE; }
 157
 158   /// This function determines if this <code>Var</code> is a number.
 159   ///
 160   /// @return true if this <code>Var</code> is an int32 or double number,
 161   /// otherwise false.
 162   bool is_number() const {
 163     return var_.type == PP_VARTYPE_INT32 ||
 164            var_.type == PP_VARTYPE_DOUBLE;
 165   }
 166
 167   /// This function determines if this <code>Var</code> is an ArrayBuffer.
 168   bool is_array_buffer() const { return var_.type == PP_VARTYPE_ARRAY_BUFFER; }
 169
 170   /// AsBool() converts this <code>Var</code> to a bool. Assumes the
 171   /// internal representation is_bool(). If it's not, it will assert in debug
 172   /// mode, and return false.
 173   ///
 174   /// @return A bool version of this <code>Var</code>.
 175   bool AsBool() const;
 176
 177   /// AsInt() converts this <code>Var</code> to an int32_t. This function
 178   /// is required because JavaScript doesn't have a concept of ints and doubles,
 179   /// only numbers. The distinction between the two is an optimization inside
 180   /// the compiler. Since converting from a double to an int may be lossy, if
 181   /// you care about the distinction, either always work in doubles, or check
 182   /// !is_double() before calling AsInt().
 183   ///
 184   /// These functions will assert in debug mode and return 0 if the internal
 185   /// representation is not is_number().
 186   ///
 187   /// @return An int32_t version of this <code>Var</code>.
 188   int32_t AsInt() const;
 189
 190   /// AsDouble() converts this <code>Var</code> to a double. This function is
 191   /// necessary because JavaScript doesn't have a concept of ints and doubles,
 192   /// only numbers. The distinction between the two is an optimization inside
 193   /// the compiler. Since converting from a double to an int may be lossy, if
 194   /// you care about the distinction, either always work in doubles, or check
 195   /// !is_double() before calling AsInt().
 196   ///
 197   /// These functions will assert in debug mode and return 0 if the internal
 198   /// representation is not is_number().
 199   ///
 200   /// @return An double version of this <code>Var</code>.
 201   double AsDouble() const;
 202
 203   /// AsString() converts this <code>Var</code> to a string. If this object is
 204   /// not a string, it will assert in debug mode, and return an empty string.
 205   ///
 206   /// @return A string version of this <code>Var</code>.
 207   std::string AsString() const;
 208
 209   /// This function returns the internal <code>PP_Var</code>
 210   /// managed by this <code>Var</code> object.
 211   ///
 212   /// @return A const reference to a <code>PP_Var</code>.
 213   const PP_Var& pp_var() const {
 214     return var_;
 215   }
 216
 217   /// Detach() detaches from the internal <code>PP_Var</code> of this
 218   /// object, keeping the reference count the same. This is used when returning
 219   /// a <code>PP_Var</code> from an API function where the caller expects the
 220   /// return value to have the reference count incremented for it.
 221   ///
 222   /// @return A detached version of this object without affecting the reference
 223   /// count.
 224   PP_Var Detach() {
 225     PP_Var ret = var_;
 226     var_ = PP_MakeUndefined();
 227     is_managed_ = true;
 228     return ret;
 229   }
 230
 231   /// DebugString() returns a short description "Var<X>" that can be used for
 232   /// logging, where "X" is the underlying scalar or "UNDEFINED" or "OBJ" as
 233   /// it does not call into the browser to get the object description.
 234   ///
 235   /// @return A string displaying the value of this <code>Var</code>. This
 236   /// function is used for debugging.
 237   std::string DebugString() const;
 238
 239   /// This class is used when calling the raw C PPAPI when using the C++
 240   /// <code>Var</code> as a possible NULL exception. This class will handle
 241   /// getting the address of the internal value out if it's non-NULL and
 242   /// fixing up the reference count.
 243   ///
 244   /// <strong>Warning:</strong> this will only work for things with exception
 245   /// semantics, i.e. that the value will not be changed if it's a
 246   /// non-undefined exception. Otherwise, this class will mess up the
 247   /// refcounting.
 248   ///
 249   /// This is a bit subtle:
 250   /// - If NULL is passed, we return NULL from get() and do nothing.
 251   ///
 252   /// - If a undefined value is passed, we return the address of a undefined
 253   ///   var from get and have the output value take ownership of that var.
 254   ///
 255   /// - If a non-undefined value is passed, we return the address of that var
 256   ///   from get, and nothing else should change.
 257   ///
 258   /// Example:
 259   ///   void FooBar(a, b, Var* exception = NULL) {
 260   ///     foo_interface->Bar(a, b, Var::OutException(exception).get());
 261   ///   }
 262   class OutException {
 263    public:
 264     /// A constructor.
 265     OutException(Var* v)
 266         : output_(v),
 267           originally_had_exception_(v && !v->is_undefined()) {
 268       if (output_) {
 269         temp_ = output_->var_;
 270       } else {
 271         temp_.padding = 0;
 272         temp_.type = PP_VARTYPE_UNDEFINED;
 273       }
 274     }
 275
 276     /// Destructor.
 277     ~OutException() {
 278       if (output_ && !originally_had_exception_)
 279         *output_ = Var(PASS_REF, temp_);
 280     }
 281
 282     PP_Var* get() {
 283       if (output_)
 284         return &temp_;
 285       return NULL;
 286     }
 287
 288    private:
 289     Var* output_;
 290     bool originally_had_exception_;
 291     PP_Var temp_;
 292   };
 293
 294  protected:
 295   PP_Var var_;
 296
 297   // |is_managed_| indicates if the instance manages |var_|.
 298   // You need to check if |var_| is refcounted to call Release().
 299   bool is_managed_;
 300
 301  private:
 302   // Prevent an arbitrary pointer argument from being implicitly converted to
 303   // a bool at Var construction. If somebody makes such a mistake, (s)he will
 304   // get a compilation error.
 305   Var(void* non_scriptable_object_pointer);
 306 };
 307
 308 }  // namespace pp
 309
 310 #endif  // PPAPI_CPP_VAR_H_