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small_uint.h
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29 
30 #ifndef TINS_SMALL_UINT_H
31 #define TINS_SMALL_UINT_H
32 
33 #include <stdint.h>
34 #include <stdexcept>
35 
36 namespace Tins {
37 class value_too_large : public std::exception {
38 public:
39  const char* what() const throw() {
40  return "Value is too large";
41  }
42 };
43 
51 template<size_t n>
52 class small_uint {
53 private:
54  template<bool cond, typename OnTrue, typename OnFalse>
55  struct if_then_else {
56  typedef OnTrue type;
57  };
58 
59  template<typename OnTrue, typename OnFalse>
60  struct if_then_else<false, OnTrue, OnFalse> {
61  typedef OnFalse type;
62  };
63 
64  template<size_t i>
65  struct best_type {
66  typedef typename if_then_else<
67  (i <= 8),
68  uint8_t,
69  typename if_then_else<
70  (i <= 16),
71  uint16_t,
72  typename if_then_else<
73  (i <= 32),
74  uint32_t,
75  uint64_t
76  >::type
77  >::type
78  >::type type;
79  };
80 
81  template<uint64_t base, uint64_t pow>
82  struct power {
83  static const uint64_t value = base * power<base, pow - 1>::value;
84  };
85 
86  template<uint64_t base>
87  struct power<base, 0> {
88  static const uint64_t value = 1;
89  };
90 public:
94  typedef typename best_type<n>::type repr_type;
95 
99  static const repr_type max_value = power<2, n>::value - 1;
100 
104  small_uint() : value() {}
105 
115  if (val > max_value) {
116  throw value_too_large();
117  }
118  value = val;
119  }
120 
124  operator repr_type() const {
125  return value;
126  }
127 private:
128  repr_type value;
129 };
130 
131 } // Tins
132 
133 #endif // TINS_SMALL_UINT_H
Definition: small_uint.h:37
small_uint()
Definition: small_uint.h:104
Represents a field of n bits.
Definition: small_uint.h:52
small_uint(repr_type val)
Copy constructs the stored value.
Definition: small_uint.h:114
static const repr_type max_value
Definition: small_uint.h:99
best_type< n >::type repr_type
Definition: small_uint.h:94