firmware/src/MemoryPool.h

#pragma once 

#include <Arduino.h>
#include <assert.h>

#include "PointerQueue.h"

/**
 * A pool based allocator
 * 
 * Eventually this routine will even be safe for ISR use...
 */
template <class T> class MemoryPool {
    PointerQueue<T> dead;

    T *buf; // our large raw block of memory

    size_t maxElements;
public:
    MemoryPool(size_t _maxElements): dead(_maxElements), maxElements(_maxElements) {
        buf = new T[maxElements];
        
        // prefill dead
        for(int i = 0; i < maxElements; i++)
            release(&buf[i]);
    }

    ~MemoryPool() {
        delete[] buf;
    }

    /// Return a queable object which has been prefilled with zeros.  Panic if no buffer is available
    T *allocZeroed() {
        T *p = allocZeroed(0);
        
        assert(p); // FIXME panic instead
        return p;
    }


    /// Return a queable object which has been prefilled with zeros - allow timeout to wait for available buffers (you probably don't want this version)
    T *allocZeroed(TickType_t maxWait) {
        T *p = dead.dequeuePtr(maxWait);
        
        if(p)
            memset(p, 0, sizeof(T));
        return p;
    }

    /// Return a queable object which is a copy of some other object
    T *allocCopy(const T &src, TickType_t maxWait = portMAX_DELAY) {
        T *p = dead.dequeuePtr(maxWait);
        
        if(p)
            *p = src;
        return p;
    }


    /// Return a buffer for use by others
    void release(T *p) {
        int res = dead.enqueue(p, 0);
        assert(res == pdTRUE);
        assert(p >= buf && (p - buf) < maxElements); // sanity check to make sure a programmer didn't free something that didn't come from this pool
    }
};