/*
 * Copyright 2014, NICTA
 *
 * This software may be distributed and modified according to the terms of
 * the BSD 2-Clause license. Note that NO WARRANTY is provided.
 * See "LICENSE_BSD2.txt" for details.
 *
 * @TAG(NICTA_BSD)
 */

// #define VERIFIED 1

#ifndef VERIFIED
#include <stdlib.h>
#include <stdio.h>
#endif

#ifndef NULL
#define NULL ((void *)0)
#endif

typedef unsigned long word_t;

struct heap {
    word_t max;
    word_t curr;
};

void
init_heap (struct heap* heap, word_t max){
    heap->curr = (word_t) malloc(max);
    //printf("%lu\n", heap->curr);
    heap->max  = heap->curr + max;
}

void*
alloc(struct heap* heap, word_t bytes){
    if(heap->curr + bytes > heap->max)
        return NULL;
    heap->curr += bytes;
    return (void*) heap->curr - bytes;
}

#ifndef VERIFIED
int
main(void){
    struct heap* h = malloc(sizeof(struct heap));
    init_heap(h, 1024);

    int i, j;
    int* ptr;

    for (i = 0; i < 1024; i++) {
        printf("%p\n", alloc(h, 1));
    }

    return 0;


    int *x = alloc(h, 0x10);
    printf("%p\n", x);
    int *y = alloc(h, 0xffffffff);
    printf("%p\n", y);
    return 0;

    /* allocate and write 128 ints to the heap */
    for (i = 0; i < 1024; i += 4){
        ptr = alloc(h, 4);
        *ptr = i;
    }

    /* check written ints correct */
    for (i = 1020; i > 0; i -= 4){
        j = *ptr;
        if(i != j){
            printf("%d != %d\n",  i, j);
        }
        ptr--;
    }

    /* check heap is full */
    void* null = alloc(h, 1);
    if(null != NULL){
        printf("null != NULL\n");
    }



    return 0;
}
#endif