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// Copyright (C) 2008-2018 Lorenzo Caminiti
// Distributed under the Boost Software License, Version 1.0 (see accompanying
// file LICENSE_1_0.txt or a copy at http://www.boost.org/LICENSE_1_0.txt).
// See: http://www.boost.org/doc/libs/release/libs/contract/doc/html/index.html
#include <boost/contract.hpp>
#include <vector>
#include <utility>
#include <cassert>
//[move
class circular_buffer :
private boost::contract::constructor_precondition<circular_buffer> {
public:
void invariant() const {
if(!moved()) { // Do not check (some) invariants for moved-from objects.
BOOST_CONTRACT_ASSERT(index() < size());
}
// More invariants here that hold also for moved-from objects (e.g.,
// all assertions necessary to successfully destroy moved-from objects).
}
// Move constructor.
circular_buffer(circular_buffer&& other) :
boost::contract::constructor_precondition<circular_buffer>([&] {
BOOST_CONTRACT_ASSERT(!other.moved());
})
{
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(!moved());
BOOST_CONTRACT_ASSERT(other.moved());
})
;
move(std::forward<circular_buffer>(other));
}
// Move assignment.
circular_buffer& operator=(circular_buffer&& other) {
// Moved-from can be (move) assigned (so no pre `!moved()` here).
boost::contract::check c = boost::contract::public_function(this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(!other.moved());
})
.postcondition([&] {
BOOST_CONTRACT_ASSERT(!moved());
BOOST_CONTRACT_ASSERT(other.moved());
})
;
return move(std::forward<circular_buffer>(other));
}
~circular_buffer() {
// Moved-from can always be destroyed (in fact no preconditions).
boost::contract::check c = boost::contract::destructor(this);
}
bool moved() const {
boost::contract::check c = boost::contract::public_function(this);
return moved_;
}
private:
bool moved_;
/* ... */
//]
public:
explicit circular_buffer(std::vector<char> const& data,
unsigned start = 0) :
boost::contract::constructor_precondition<circular_buffer>([&] {
BOOST_CONTRACT_ASSERT(start < data.size());
}),
moved_(false),
data_(data),
index_(start)
{
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(!moved());
})
;
}
// Copy constructor.
circular_buffer(circular_buffer const& other) :
boost::contract::constructor_precondition<circular_buffer>([&] {
BOOST_CONTRACT_ASSERT(!other.moved());
})
{
boost::contract::check c = boost::contract::constructor(this)
.postcondition([&] {
BOOST_CONTRACT_ASSERT(!moved());
})
;
copy(other);
}
// Copy assignment.
circular_buffer& operator=(circular_buffer const& other) {
// Moved-from can be (copy) assigned (so no pre `!moved()` here).
boost::contract::check c = boost::contract::public_function(this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(!other.moved());
})
.postcondition([&] {
BOOST_CONTRACT_ASSERT(!moved());
})
;
return copy(other);
}
char read() {
boost::contract::check c = boost::contract::public_function(this)
.precondition([&] {
BOOST_CONTRACT_ASSERT(!moved());
})
;
unsigned i = index_++;
if(index_ == data_.size()) index_ = 0; // Circular.
return data_.at(i);
}
private:
circular_buffer& copy(circular_buffer const& other) {
data_ = other.data_;
index_ = other.index_;
moved_ = false;
return *this;
}
circular_buffer& move(circular_buffer&& other) {
data_ = std::move(other.data_);
index_ = std::move(other.index_);
moved_ = false;
other.moved_ = true; // Mark moved-from object.
return *this;
}
std::vector<char> data_;
unsigned index_;
public:
unsigned index() const {
boost::contract::check c = boost::contract::public_function(this);
return index_;
}
unsigned size() const {
boost::contract::check c = boost::contract::public_function(this);
return data_.size();
}
};
int main() {
struct err {};
boost::contract::set_precondition_failure(
[] (boost::contract::from) { throw err(); });
{
circular_buffer x({'a', 'b', 'c', 'd'}, 2);
assert(x.read() == 'c');
circular_buffer y1 = x; // Copy constructor.
assert(y1.read() == 'd');
assert(x.read() == 'd');
circular_buffer y2({'h'});
y2 = x; // Copy assignment.
assert(y2.read() == 'a');
assert(x.read() == 'a');
circular_buffer z1 = std::move(x); // Move constructor.
assert(z1.read() == 'b');
// Calling `x.read()` would fail `!moved()` precondition.
x = y1; // Moved-from `x` can be copy assigned.
assert(x.read() == 'a');
assert(y1.read() == 'a');
circular_buffer z2({'k'});
z2 = std::move(x); // Move assignment.
assert(z2.read() == 'b');
// Calling `x.read()` would fail `!moved()` precondition.
x = std::move(y2); // Moved-from `x` can be move assigned.
assert(x.read() == 'b');
// Calling `y2.read()` would fail `!moved()` precondition.
} // Moved-from `y2` can be destroyed.
return 0;
}
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