RingBuffer.h

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/**
 * @file RingBuffer.h
 * @author Roman Bapst <bapstroman@gmail.com>
 * Template RingBuffer.
 */

#include <inttypes.h>
#include <cstdio>
#include <cstring>

template <typename data_type>
class RingBuffer
{
public:
    RingBuffer()
    {
        if (allocate(1)) {
            // initialize with one empty sample
            data_type d = {};
            push(d);
        }
    }
    ~RingBuffer() { delete[] _buffer; }

    // no copy, assignment, move, move assignment
    RingBuffer(const RingBuffer &) = delete;
    RingBuffer &operator=(const RingBuffer &) = delete;
    RingBuffer(RingBuffer &&) = delete;
    RingBuffer &operator=(RingBuffer &&) = delete;

    bool allocate(uint8_t size)
    {
        if (_buffer != nullptr) {
            delete[] _buffer;
        }

        _buffer = new data_type[size];

        if (_buffer == nullptr) {
            return false;
        }

        _size = size;

        _head = 0;
        _tail = 0;

        // set the time elements to zero so that bad data is not retrieved from the buffers
        for (uint8_t index = 0; index < _size; index++) {
            _buffer[index] = {};
        }

        _first_write = true;

        return true;
    }

    void unallocate()
    {
        delete[] _buffer;
        _buffer = nullptr;
    }

    void push(const data_type &sample)
    {
        uint8_t head_new = _head;

        if (!_first_write) {
            head_new = (_head + 1) % _size;
        }

        _buffer[head_new] = sample;
        _head = head_new;

        // move tail if we overwrite it
        if (_head == _tail && !_first_write) {
            _tail = (_tail + 1) % _size;

        } else {
            _first_write = false;
        }
    }

    uint8_t get_length() const { return _size; }

    data_type &operator[](const uint8_t index) { return _buffer[index]; }

    const data_type &get_newest() { return _buffer[_head]; }
    const data_type &get_oldest() { return _buffer[_tail]; }

    uint8_t get_oldest_index() const { return _tail; }

    bool pop_first_older_than(const uint64_t &timestamp, data_type *sample)
    {
        // start looking from newest observation data
        for (uint8_t i = 0; i < _size; i++) {
            int index = (_head - i);
            index = index < 0 ? _size + index : index;

            if (timestamp >= _buffer[index].time_us && timestamp - _buffer[index].time_us < (uint64_t)1e5) {

                *sample = _buffer[index];

                // Now we can set the tail to the item which comes after the one we removed
                // since we don't want to have any older data in the buffer
                if (index == _head) {
                    _tail = _head;
                    _first_write = true;

                } else {
                    _tail = (index + 1) % _size;
                }

                _buffer[index].time_us = 0;

                return true;
            }

            if (index == _tail) {
                // we have reached the tail and haven't got a match
                return false;
            }
        }

        return false;
    }

    int get_total_size() { return sizeof(*this) + sizeof(data_type) * _size; }

private:
    data_type *_buffer{nullptr};

    uint8_t _head{0};
    uint8_t _tail{0};
    uint8_t _size{0};

    bool _first_write{true};
};