ceph/src/boost/libs/contract/example/mitchell02/dictionary.cpp

   1
   2 // Copyright (C) 2008-2018 Lorenzo Caminiti
   3 // Distributed under the Boost Software License, Version 1.0 (see accompanying
   4 // file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
   5 // See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
   6
   7 //[mitchell02_dictionary
   8 #include <boost/contract.hpp>
   9 #include <utility>
  10 #include <map>
  11 #include <cassert>
  12
  13 template<typename K, typename T>
  14 class dictionary {
  15     friend class boost::contract::access;
  16
  17     void invariant() const {
  18         BOOST_CONTRACT_ASSERT(count() >= 0); // Non-negative count.
  19     }
  20
  21 public:
  22     /* Creation */
  23
  24     // Create empty dictionary.
  25     dictionary() {
  26         boost::contract::check c = boost::contract::constructor(this)
  27             .postcondition([&] {
  28                 BOOST_CONTRACT_ASSERT(count() == 0); // Empty.
  29             })
  30         ;
  31     }
  32
  33     // Destroy dictionary.
  34     virtual ~dictionary() {
  35         // Check invariants.
  36         boost::contract::check c = boost::contract::destructor(this);
  37     }
  38
  39     /* Basic Queries */
  40
  41     // Number of key entries.
  42     int count() const {
  43         // Check invariants.
  44         boost::contract::check c = boost::contract::public_function(this);
  45         return items_.size();
  46     }
  47
  48     // Has entry for key?
  49     bool has(K const& key) const {
  50         bool result;
  51         boost::contract::check c = boost::contract::public_function(this)
  52             .postcondition([&] {
  53                 // Empty has no key.
  54                 if(count() == 0) BOOST_CONTRACT_ASSERT(!result);
  55             })
  56         ;
  57
  58         return result = (items_.find(key) != items_.end());
  59     }
  60
  61     // Value for a given key.
  62     T const& value_for(K const& key) const {
  63         boost::contract::check c = boost::contract::public_function(this)
  64             .precondition([&] {
  65                 BOOST_CONTRACT_ASSERT(has(key)); // Has key.
  66             })
  67         ;
  68
  69         // Find != end because of precondition (no defensive programming).
  70         return items_.find(key)->second;
  71     }
  72
  73     /* Commands */
  74
  75     // Add value of a given key.
  76     void put(K const& key, T const& value) {
  77         boost::contract::old_ptr<int> old_count = BOOST_CONTRACT_OLDOF(count());
  78         boost::contract::check c = boost::contract::public_function(this)
  79             .precondition([&] {
  80                 BOOST_CONTRACT_ASSERT(!has(key)); // Has not key already.
  81             })
  82             .postcondition([&] {
  83                 BOOST_CONTRACT_ASSERT(count() == *old_count + 1); // Count inc.
  84                 BOOST_CONTRACT_ASSERT(has(key)); // Has key.
  85                 // Value set for key.
  86                 BOOST_CONTRACT_ASSERT(value_for(key) == value);
  87             })
  88         ;
  89
  90         items_.insert(std::make_pair(key, value));
  91     }
  92
  93     // Remove value for given key.
  94     void remove(K const& key) {
  95         boost::contract::old_ptr<int> old_count = BOOST_CONTRACT_OLDOF(count());
  96         boost::contract::check c = boost::contract::public_function(this)
  97             .precondition([&] {
  98                 BOOST_CONTRACT_ASSERT(has(key)); // Has key.
  99             })
 100             .postcondition([&] {
 101                 BOOST_CONTRACT_ASSERT(count() == *old_count - 1); // Count dec.
 102                 BOOST_CONTRACT_ASSERT(!has(key)); // Has not key.
 103             })
 104         ;
 105
 106         items_.erase(key);
 107     }
 108
 109 private:
 110     std::map<K, T> items_;
 111 };
 112
 113 int main() {
 114     std::string const js = "John Smith";
 115
 116     dictionary<std::string, int> ages;
 117     assert(!ages.has(js));
 118
 119     ages.put(js, 23);
 120     assert(ages.value_for(js) == 23);
 121
 122     ages.remove(js);
 123     assert(ages.count() == 0);
 124
 125     return 0;
 126 }
 127 //]
 128