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value.hpp
1 #ifndef PROTON_VALUE_HPP
2 #define PROTON_VALUE_HPP
3 
4 /*
5  *
6  * Licensed to the Apache Software Foundation (ASF) under one
7  * or more contributor license agreements. See the NOTICE file
8  * distributed with this work for additional information
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11  * "License"); you may not use this file except in compliance
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13  *
14  * http://www.apache.org/licenses/LICENSE-2.0
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16  * Unless required by applicable law or agreed to in writing,
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19  * KIND, either express or implied. See the License for the
20  * specific language governing permissions and limitations
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23  */
24 
25 #include "./codec/encoder.hpp"
26 #include "./codec/decoder.hpp"
27 #include "./internal/type_traits.hpp"
28 #include "./scalar.hpp"
29 #include "./types_fwd.hpp"
30 
31 #include <iosfwd>
32 
33 namespace proton {
34 
35 namespace internal {
36 
38 class value_base {
39  public:
41  PN_CPP_EXTERN type_id type() const;
42 
44  PN_CPP_EXTERN bool empty() const;
45 
46  protected:
47  internal::data& data();
48  internal::data data_;
49 
50  friend class value_ref;
51  friend class codec::encoder;
52  friend class codec::decoder;
53 };
54 
55 } // internal
56 
60 class value : public internal::value_base, private internal::comparable<value> {
61  private:
62  // Enabler for encodable types excluding proton::value.
63  template<class T, class U=void> struct assignable :
64  public internal::enable_if<codec::is_encodable<T>::value, U> {};
65  template<class U> struct assignable<value, U> {};
66 
67  public:
69  PN_CPP_EXTERN value();
70 
73  PN_CPP_EXTERN value(const value&);
74  PN_CPP_EXTERN value& operator=(const value&);
75 #if PN_CPP_HAS_RVALUE_REFERENCES
76  PN_CPP_EXTERN value(value&&);
77  PN_CPP_EXTERN value& operator=(value&&);
78 #endif
79 
82  template <class T> value(const T& x, typename assignable<T>::type* = 0) { *this = x; }
83 
85  template <class T> typename assignable<T, value&>::type operator=(const T& x) {
86  codec::encoder e(*this);
87  e << x;
88  return *this;
89  }
90 
92  PN_CPP_EXTERN void clear();
93 
95  template<class T> void get(T &t) const;
96  template<class T> T get() const;
97  PN_CPP_EXTERN int64_t as_int() const;
98  PN_CPP_EXTERN uint64_t as_uint() const;
99  PN_CPP_EXTERN double as_double() const;
100  PN_CPP_EXTERN std::string as_string() const;
102 
104  friend PN_CPP_EXTERN void swap(value&, value&);
105 
108  friend PN_CPP_EXTERN bool operator==(const value& x, const value& y);
109  friend PN_CPP_EXTERN bool operator<(const value& x, const value& y);
111 
112  friend PN_CPP_EXTERN std::ostream& operator<<(std::ostream&, const value&);
113 };
114 
115 namespace internal {
116 
117 // value_ref is a `pn_data_t* p` that can be returned as a value& and used to modify
118 // the underlying value in-place.
119 //
120 // Classes with a value_ref member can return it as a value& in accessor functions.
121 // It can also be used to copy a pn_data_t* p to a proton::value via: value(value_ref(p));
122 // None of the constructors make copies, they just refer to the same value.
123 //
124 class value_ref : public value {
125  public:
126  value_ref(pn_data_t* = 0);
127  value_ref(const internal::data&);
128  value_ref(const value_base&);
129 
130  // Use refer() not operator= to avoid confusion with value op=
131  void refer(pn_data_t*);
132  void refer(const internal::data&);
133  void refer(const value_base&);
134 
135  // Reset to refer to nothing, release existing references. Equivalent to refer(0).
136  void reset();
137 
138  // Assignments to value_ref means assigning to the value.
139  template <class T> value_ref& operator=(const T& x) {
140  static_cast<value&>(*this) = x;
141  return *this;
142  }
143 };
144 
145 }
146 
147 
150 template<class T> T get(const value& v) { T x; get(v, x); return x; }
151 
157 template<class T> void get(const value& v, T& x) { codec::decoder d(v, true); d >> x; }
158 
161 template<class T> T coerce(const value& v) { T x; coerce(v, x); return x; }
162 
168 template<class T> void coerce(const value& v, T& x) {
169  codec::decoder d(v, false);
170  if (type_id_is_scalar(v.type())) {
171  scalar s;
172  d >> s;
173  x = internal::coerce<T>(s);
174  } else {
175  d >> x;
176  }
177 }
178 
180 template<> inline void get<null>(const value& v, null&) {
181  assert_type_equal(NULL_TYPE, v.type());
182 }
183 
185 PN_CPP_EXTERN std::string to_string(const value& x);
186 
188 template<class T> void value::get(T &x) const { x = proton::get<T>(*this); }
189 template<class T> T value::get() const { return proton::get<T>(*this); }
190 inline int64_t value::as_int() const { return proton::coerce<int64_t>(*this); }
191 inline uint64_t value::as_uint() const { return proton::coerce<uint64_t>(*this); }
192 inline double value::as_double() const { return proton::coerce<double>(*this); }
193 inline std::string value::as_string() const { return proton::coerce<std::string>(*this); }
195 
196 } // proton
197 
198 #endif // PROTON_VALUE_HPP
A holder for an instance of any scalar AMQP type.
Definition: scalar.hpp:35
T get(const value &v)
Get a contained value of type T.
Definition: value.hpp:150
The null type, contains no data.
Definition: type_id.hpp:39
void get< null >(const value &v, null &)
Special case for get(), just checks that value contains NULL.
Definition: value.hpp:180
Experimental - Stream-like encoder from AMQP bytes to C++ values.
Definition: encoder.hpp:45
value()
Create a null value.
assignable< T, value & >::type operator=(const T &x)
Assign from any allowed type T.
Definition: value.hpp:85
friend void swap(value &, value &)
swap values
value(const T &x, typename assignable< T >::type *=0)
Construct from any allowed type T.
Definition: value.hpp:82
void coerce(const value &v, T &x)
Like coerce(const value&) but assigns the value to a reference instead of returning it...
Definition: value.hpp:168
std::string to_string(const internal::scalar_base &x)
Return a readable string representation of x for display purposes.
type_id
An identifier for AMQP types.
Definition: type_id.hpp:38
T coerce(const value &v)
Coerce the contained value to type T.
Definition: value.hpp:161
Forward declarations for all the C++ types used by Proton to represent AMQP types.
A holder for any AMQP value, simple or complex.
Definition: value.hpp:60
void assert_type_equal(type_id want, type_id got)
Throw a conversion_error if want != got with a message including the names of the types...
void clear()
Reset the value to null.
Type traits for mapping between AMQP and C++ types.
Definition: annotation_key.hpp:28
Experimental - Stream-like decoder from AMQP bytes to C++ values.
Definition: decoder.hpp:51