ardupilot/libraries/AP_Buffer/AP_Buffer.h

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2013-05-29 20:53:15 -03:00
// -*- tab-width: 4; Mode: C++; c-basic-offset: 4; indent-tabs-mode: nil -*-
/// @file AP_Buffer.h
/// @brief fifo (queue) buffer template class
#pragma once
2012-11-19 20:57:50 -04:00
#include <stdint.h>
/// @class AP_Buffer
template <class T, uint8_t SIZE>
class AP_Buffer {
public:
/// Constructor
///
AP_Buffer();
/// clear - removes all elements from the queue
///
void clear();
/// push_back - adds an item to the end of the buffer.
/// If the buffer is full, the oldest element (i.e. the element at the begin) is removed
/// @param item
void push_back( const T &item );
/// pop_front - removes an element from the beginning of the
/// buffer (i.e. the oldest element) and returns it in ret.
/// @param ret : the removed element, if exists
/// @return : true if successful, false if not
bool pop_front(T &ret);
/// peek - returns a reference to an element of the buffer
/// if position isn't valid (i.e. >= size()) 0 is returned
/// @param position : index of the element
/// "0" is the oldest, size()-1 is the newest
/// @return
const T& peek(uint8_t position) const;
T& peek_mutable(uint8_t position);
/// front - return a reference to the element at the begin of the queue (i.e. the oldest element)
/// If the queue is empty, 0 is returned.
/// @return : oldest element
const T& front() const { return this->peek(0); }
/// size - returns the number of elements in the queue
/// @return
uint8_t size() const { return _num_items; }
/// is_full - return true if the queue is full (i.e. size() == SIZE)
/// @return
bool is_full() const { return _num_items >= SIZE; }
/// is_empty - returns true if the queue is empty
/// @return
bool is_empty() const { return _num_items == 0; }
private:
uint8_t _num_items; // number of items in the buffer
uint8_t _head; // first item in the buffer (will be returned with the next pop_front call)
T _buff[SIZE]; // x values of each point on the curve
};
// Typedef for convenience - add more as needed
typedef AP_Buffer<float,5> AP_BufferFloat_Size5;
typedef AP_Buffer<float,15> AP_BufferFloat_Size15;
template <class T, uint8_t SIZE>
AP_Buffer<T,SIZE>::AP_Buffer() :
_num_items(0), _head(0)
{
}
template <class T, uint8_t SIZE>
void AP_Buffer<T,SIZE>::clear() {
// clear the curve
_num_items = 0;
_head = 0;
}
template <class T, uint8_t SIZE>
void AP_Buffer<T,SIZE>::push_back( const T &item )
{
// determine position of new item
uint8_t tail = _head + _num_items;
if( tail >= SIZE ) {
tail -= SIZE;
}
// add item to buffer
_buff[tail] = item;
// increment number of items
if( _num_items < SIZE ) {
_num_items++;
}else{
// no room for new items so drop oldest item
_head++;
if( _head >= SIZE ) {
_head = 0;
}
}
}
template <class T, uint8_t SIZE>
bool AP_Buffer<T,SIZE>::pop_front(T &ret)
{
if(_num_items == 0) {
// buffer is empty
return false;
}
// get next value in buffer
ret = _buff[_head];
// increment to next point
_head++;
if( _head >= SIZE )
_head = 0;
// reduce number of items
_num_items--;
// success
return true;
}
template <class T, uint8_t SIZE>
const T& AP_Buffer<T,SIZE>::peek(uint8_t position) const
{
uint8_t j = _head + position;
// wrap around if necessary
if( j >= SIZE )
j -= SIZE;
// return desired value
return _buff[j];
}
template <class T, uint8_t SIZE>
T& AP_Buffer<T,SIZE>::peek_mutable(uint8_t position)
{
uint8_t j = _head + position;
// wrap around if necessary
if( j >= SIZE )
j -= SIZE;
// return desired value
return _buff[j];
}