MemoryFree.h

// Filename: MemoryFree.h
// Version 1.5 08/15/13 JS MiloCreek
// MemoryFree library based on code posted here:
// http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1213583720/15
//
// Extended by Matthew Murdoch to include walking of the free list.

#ifndef MEMORY_FREE_H
#define MEMORY_FREE_H

#ifdef __cplusplus
extern "C" {
#endif

  int freeMemory();

#ifdef  __cplusplus
}
#endif

#endif



#if (ARDUINO >= 100)
#include <Arduino.h>
#else
#include
#endif

extern unsigned int __heap_start;
extern void *__brkval;

/*
 * The free list structure as maintained by the
 * avr-libc memory allocation routines.
 */
struct __freelist {
    size_t sz;
    struct __freelist *nx;
};

/* The head of the free list structure */
extern struct __freelist *__flp;



/* Calculates the size of the free list */
int freeListSize() {
    struct __freelist* current;
    int total = 0;
    
    for (current = __flp; current; current = current->nx) {
        total += 2; /* Add two bytes for the memory block's header  */
        total += (int) current->sz;
    }
    
    return total;
}

int freeMemory() {
    int free_memory;
    
    if ((int)__brkval == 0) {
        free_memory = ((int)&free_memory) - ((int)&__heap_start);
    } else {
        free_memory = ((int)&free_memory) - ((int)__brkval);
        free_memory += freeListSize();
    }
    return free_memory;
}