CircularBuffer.h

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/* Copyright (c) 2015-2018 Skyward Experimental Rocketry
 * Authors: Luca Erbetta, Davide Mor
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */
 
#pragma once
 
#include <cstring>
#include <stdexcept>
#include <type_traits>
 
using std::range_error;
 
namespace Boardcore
{
 
template <typename T, unsigned int Size>
class CircularBuffer
{
    static_assert(Size > 0, "Circular buffer size must be greater than 0!");
 
public:
    CircularBuffer() {}
 
    virtual ~CircularBuffer() {}
 
    T& put(const T& elem)
    {
        buffer[writePtr] = elem;
        T& added         = buffer[writePtr];
 
        // Advance the read pointer if the two pointers match
        if (!empty && writePtr == readPtr)
            readPtr = (readPtr + 1) % Size;
 
        // Advance the write pointer
        writePtr = (writePtr + 1) % Size;
 
        empty = false;
 
        return added;
    }
 
    T& get(unsigned int i = 0)
    {
        // Here we need to explicitly specify the name of this class because we
        // DO NOT want to call the version of count() overridden by a derived
        // class: this is done to avoid deadlocks, as a derived class may
        // synchronize get() and count() with a mutex: calling count() from
        // get() would thus require locking the same mutex twice, causing a
        // deadlock.
        if (i < CircularBuffer<T, Size>::count())
        {
            int ptr = (readPtr + i) % Size;
            return buffer[ptr];
        }
        else
        {
            throw range_error("Circular buffer index out of range");
        }
    }
 
    T& last() { return get(count() - 1); }
 
    const T& pop()
    {
        if (!empty)
        {
            size_t ptr = readPtr;
            readPtr    = (readPtr + 1) % Size;
 
            empty = readPtr == writePtr;
 
            return buffer[ptr];
        }
        else
        {
            throw range_error("Circular buffer is empty!");
        }
    }
 
    size_t count() const
    {
        if (empty)
            return 0;
        if (writePtr > readPtr)
            return writePtr - readPtr;
        else
            return Size - readPtr + writePtr;
    }
 
    bool isEmpty() const { return empty; }
 
    bool isFull() const
    {
        // Same as in get(): explicitly specify the name of the class to avoid
        // deadlocks!
        return CircularBuffer<T, Size>::count() == Size;
    }
    size_t getSize() const { return Size; }
 
protected:
    T buffer[Size];
 
    size_t writePtr = 0;
    size_t readPtr  = 0;
    bool empty      = true;
};
 
}  // namespace Boardcore