环缓冲托管实现

// 这个缓冲将被用作ring_buffer测试class x_buffer{private:#pragma pack(1)typedef struct {volatile size_t _rd;volatile size_t _wd;volatile size_t _size;volatile bool   _empty;char _data[1];}x_buffer_data, *x_buffer_data_ptr;x_buffer_data_ptr _buffer_data;public:x_buffer():_buffer_data(nullptr){}x_buffer(size_t size){_buffer_data = (x_buffer_data_ptr)( new char(size + sizeof(x_buffer_data)) );_buffer_data->_size = size;_buffer_data._rd = _buffer_data._wd = 0;_buffer_data._empty = true;memset(_buffer_data->_data, 0, _buffer_data->_size);}char* base(){return _buffer_data._data;}const char* base(){return _buffer_data._data;}size_t capacity(){return _buffer_data._size();}size_t rd(){return _buffer_data._rd;}char* rd_ptr(){return base() + _buffer_data._rd;}void set_rd(size_t rd_){_buffer_data._rd = rd_;}size_t wd(){return _buffer_data._wd;}char* wd_ptr(){return base() + _buffer_data._wd;}void set_wd(size_t wd_){_buffer_data._wd = wd_;}bool empty(){return _buffer_data._empty;}void set_empty(bool empty_){_buffer_data._empty = empty_;}};// ring托管类template<class _Buffer>class ring_buffer{private:_Buffer _buffer;public:ring_buffer(){}ring_buffer(const _Buffer& buffer):_buffer(buffer){}~ring_buffer(){}void assign(_Buffer&& buffer){_buffer = std::forward<_Buffer>(buffer);}// 写入内容size_t write(const char* value, size_t len){if (_buffer.wd() == _buffer.rd() && !_buffer.empty())return -1;if (_buffer.wd() > _buffer.rd() && _buffer.capacity() + 1 - _buffer.wd() < len && _buffer.capacity() + 1 - _buffer.wd() + _buffer.rd() <= len)return -1;else if (_buffer.wd() < _buffer.rd() && _buffer.rd() <= _buffer.wd() + len)return -1;if (_buffer.capacity() >= _buffer.wd() + len){memcpy(_buffer.wd_ptr(), value, len);_buffer.set_wd(_buffer.wd() + len);}else{size_t sublen = _buffer.capacity() - _buffer.wd();memcpy(_buffer.wd_ptr(), value, sublen);memcpy(_buffer.base(), value + sublen, len - sublen);_Buffer.set_wd(len - sublen);}if (_buffer.wd() == _buffer.rd())_buffer.set_empty(false);return len;}size_t write(const char* value){return write(value, strlen(value));}// 读取指定长度size_t read(const char* value, size_t len){if (_buffer.wd() == _buffer.rd() && _buffer.empty())return -1;else if (_buffer.wd() > _buffer.rd() && _buffer.wd() < len + _buffer.rd())return -1;else if (_buffer.capacity() - _buffer.rd() < len && _buffer.wd() + (_buffer.capacity() - _buffer.rd()) < len)return -1;if (_buffer.capacity() >= _buffer.rd() + len){memcpy(value, _buffer.rd_ptr(), len);_buffer.set_rd(_buffer.rd() + len);}else{size_t sublen = _buffer.capacity() - _buffer.rd();memcpy(value, _buffer.rd_ptr(), sublen);memcpy(value + sublen, _buffer.base(), len - sublen);_buffer.set_rd(len - sublen);}if (_buffer.wd() == _buffer.rd())_buffer.set_empty(true);return len;}// 读取全部size_t read(const char* value){if (_buffer.wd() == _buffer.rd() && _buffer.empty())return -1;size_t len = 0;if (_buffer.wd() > _buffer.rd()){memcpy(value, _buffer.rd_ptr(), _buffer.wd() - _buffer.rd());len = _buffer.wd() - _buffer.rd();}else{size_t sublen = _buffer.capacity() - _buffer.rd();memcpy(value, _buffer.rd_ptr(), sublen);memcpy(value + sublen, _buffer.base(), _buffer.wd());len = sublen + _buffer.wd();}_buffer.set_rd(_buffer.wd());_buffer.set_empty(true);return len;}};

解释：期望实现一个环形缓冲托管方法，可以托管任何buffer（主要用作共享内存，所以类型用了char）

除了托管上面的测试buff，还可以用在一些static_buffer上面。譬如：template<size_t size>class static_buffer{char _data[size];.....}。

规定了被托管对象一定要有的一些函数成员。