#include "c.h"
struct block {
        struct block *next;
        char *limit;
        char *avail;
};
union align {
        long l;
        char *p;
        double d;
        int (*f)(void);
};
union header {
        struct block b;
        union align a;
};
#ifdef PURIFY
union header *arena[3];

void *allocate(unsigned long n, unsigned a) {
        union header *new = malloc(sizeof *new + n);

        assert(a < NELEMS(arena));
        if (new == NULL) {
                error("insufficient memory\n");
                exit(1);
        }
        new->b.next = (void *)arena[a];
        arena[a] = new;
        return new + 1;
}

void deallocate(unsigned a) {
        union header *p, *q;

        assert(a < NELEMS(arena));
        for (p = arena[a]; p; p = q) {
                q = (void *)p->b.next;
                free(p);
        }
        arena[a] = NULL;
}

void *newarray(unsigned long m, unsigned long n, unsigned a) {
        return allocate(m*n, a);
}
#else
static struct block
         first[] = {  { NULL },  { NULL },  { NULL } },
        *arena[] = { &first[0], &first[1], &first[2] };
static struct block *freeblocks;

void *allocate(unsigned long n, unsigned a) {
        struct block *ap;

        assert(a < NELEMS(arena));
        assert(n > 0);
        ap = arena[a];
        n = roundup(n, sizeof (union align));
        while (n > ap->limit - ap->avail) {
                if ((ap->next = freeblocks) != NULL) {
		        freeblocks = freeblocks->next;
		        ap = ap->next;
		} else
		        {
			        unsigned m = sizeof (union header) + n + 10*1024;
			        ap->next = malloc(m);
			        ap = ap->next;
			        if (ap == NULL) {
			                error("insufficient memory\n");
			                exit(1);
			        }
			        ap->limit = (char *)ap + m;
			}
		ap->avail = (char *)((union header *)ap + 1);
		ap->next = NULL;
		arena[a] = ap;

        }
        ap->avail += n;
        return ap->avail - n;
}

void *newarray(unsigned long m, unsigned long n, unsigned a) {
        return allocate(m*n, a);
}
void deallocate(unsigned a) {
        assert(a < NELEMS(arena));
        arena[a]->next = freeblocks;
        freeblocks = first[a].next;
        first[a].next = NULL;
        arena[a] = &first[a];
}
#endif
