#include "Memory.h"
#define NULL 0

struct Malloc {
void *a;
struct Malloc *next;
int size;
int isfree;
};

struct Malloc *malloc_begin = NULL;

/* find first free region large enough */
struct Malloc* findFirstFree(size_t size) {
    struct Malloc * head = malloc_begin;
    struct Malloc * prev = NULL;
    if (!head) {
        head=sbrk(sizeof(struct Malloc));
        if (!head) return NULL;
        head->a=sbrk(size);
        if (!head->a) return NULL;
        head->next=NULL;
        head->size=size;
        head->isfree=0;
        return head;
    }
    while (head) {
        if (head->isfree && head->size >= size) {
            return head;
        }
        prev=head;
        head=head->next;
    }
    /* not found, so allocate */
    prev->next=head=sbrk(sizeof(struct Malloc));
    if (!head) return NULL;
    head->a=sbrk(size);
    if (!head->) return NULL;
    head->size=size;
    head->isfree=0;
    return head;    
}

void* calloc(size_t nmemb, size_t size){
    struct Malloc * mem = findFirstFree(nmemb*size);
    if (!mem) return NULL;

    /* TODO: clear memory */
    return mem->a;    
}

void* malloc(size_t size){
    struct Malloc * mem = findFirstFree(size);
    if (!mem) return NULL;
    
    return mem->a;
}

void free(void *ptr){
    struct Malloc * head = malloc_begin;
    while (head) {
        if (head->a==ptr) {
            head->isfree=1;
            return;
        }
        head=head->next;
    }
    fprintf(stderr,"attempt to free memory unknown to allocator\n"); return;
}