#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>

#ifndef TEST_SIZE
    #define TEST_SIZE 16
#endif

char* arenas[20];
size_t numArenas;

size_t newArenaGap = 8192;

size_t nearestArena(char* ptr) 
{
    size_t bestGap = newArenaGap;
    size_t best;
    for (int i = 0; i < numArenas; ++i) {
        size_t gap = labs(ptr-arenas[i]);
        if (gap < bestGap) {
            best = i;
            bestGap = gap;
        }
    }
    if (bestGap < newArenaGap)
        return best;
    arenas[numArenas] = ptr;
    return numArenas++;
}

void doMalloc(size_t size) {
    char* mem = (char*) malloc(size);
    if (newArenaGap < size*2)
        newArenaGap = size*2;
    size_t i = nearestArena(mem);
    if (arenas[i] != mem) {
        ptrdiff_t delta = (char*)mem - (char*)arenas[i];
        printf("malloc(%zu)\t= %p (%c%+zd)\n", size, mem, 'p'+i, delta);
    } else {
        printf("malloc(%zu)\t= %p (%c)\n", size, mem,'p'+i);
    }
}

int main()
{
    for(int i = 0; i < 16; ++i) {
        doMalloc(TEST_SIZE);
        doMalloc(TEST_SIZE*(2<<i));
    }
    return 0;
}