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/////////////////////////////////////////////////////////////////////////////
/// @file buffer_view.h
/// Buffer reference type for the Paho MQTT C++ library.
/// @date April 18, 2017
/// @author Frank Pagliughi
/////////////////////////////////////////////////////////////////////////////
/*******************************************************************************
* Copyright (c) 2017-2020 Frank Pagliughi <fpagliughi@mindspring.com>
*
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v2.0
* and Eclipse Distribution License v1.0 which accompany this distribution.
*
* The Eclipse Public License is available at
* http://www.eclipse.org/legal/epl-v20.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Frank Pagliughi - initial implementation and documentation
*******************************************************************************/
#ifndef __mqtt_buffer_view_h
#define __mqtt_buffer_view_h
#include <iostream>
#include "mqtt/types.h"
namespace mqtt {
/////////////////////////////////////////////////////////////////////////////
/**
* A reference to a contiguous sequence of items, with no ownership.
* This simply contains a pointer to a const array of items, and a size.
* This is a similar, but simplified version of the std::string_view
* class(es) in the C++17 standard.
*/
template <typename T>
class buffer_view
{
public:
/** The type of items to be held in the queue. */
using value_type = T;
/** The type used to specify number of items in the container. */
using size_type = size_t;
private:
/** Const pointer to the data array */
const value_type* data_;
/** The size of the array */
size_type sz_;
public:
/**
* Constructs a buffer view.
* @param data The data pointer
* @param n The number of items
*/
buffer_view(const value_type* data, size_type n) : data_(data), sz_(n) {}
/**
* Constructs a buffer view to a whole string.
* This the starting pointer and length of the whole string.
* @param str The string.
*/
buffer_view(const std::basic_string<value_type>& str)
: data_(str.data()), sz_(str.size()) {}
/**
* Gets a pointer the first item in the view.
* @return A const pointer the first item in the view.
*/
const value_type* data() const { return data_; }
/**
* Gets the number of items in the view.
* @return The number of items in the view.
*/
size_type size() const { return sz_; }
/**
* Gets the number of items in the view.
* @return The number of items in the view.
*/
size_type length() const { return sz_; }
/**
* Access an item in the view.
* @param i The index of the item.
* @return A const reference to the requested item.
*/
const value_type& operator[](size_t i) const { return data_[i]; }
/**
* Gets a copy of the view as a string.
* @return A copy of the view as a string.
*/
std::basic_string<value_type> str() const {
return std::basic_string<value_type>(data_, sz_);
}
/**
* Gets a copy of the view as a string.
* @return A copy of the view as a string.
*/
string to_string() const {
static_assert(
sizeof(char) == sizeof(T), "can only get string for char or byte buffers"
);
return string(reinterpret_cast<const char*>(data_), sz_);
}
};
/**
* Stream inserter for a buffer view.
* This does a binary write of the data in the buffer.
* @param os The output stream.
* @param buf The buffer reference to write.
* @return A reference to the output stream.
*/
template <typename T>
std::ostream& operator<<(std::ostream& os, const buffer_view<T>& buf) {
if (buf.size() > 0)
os.write(buf.data(), sizeof(T) * buf.size());
return os;
}
/** A buffer view for character string data. */
using string_view = buffer_view<char>;
/** A buffer view for binary data */
using binary_view = buffer_view<char>;
/////////////////////////////////////////////////////////////////////////////
// end namespace mqtt
} // namespace mqtt
#endif // __mqtt_buffer_view_h
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