#include <string.h>
typedef struct {
    unsigned int size;
    unsigned int current;
    unsigned char data[1];
} heapPart;
typedef struct {
    heapPart *primary;
    heapPart *secondary;
    unsigned int size;
    unsigned int current;
} heap;

void scan(heap *h) {
    heapPart *part = h->primary;
    unsigned int i;
    for (i = 0; i < h->current; i++) {
        unsigned int j;
        for (j = 0; j < part->current; j++) {
            void *p = *(void **) (part->data + j);
            if (p >= part->data && p < part->data + part->size) {
                *(void **) (part->data + j) = h->secondary + h->current;
                memcpy(h->secondary + h->current, p, sizeof(void *));
                h->current++;
            }
        }
        part++;
    }
}

void collect(heap *h) {
    scan(h);
    heapPart *tmp = h->primary;
    h->primary = h->secondary;
    h->secondary = tmp;
    h->current = 0;
}

void *alloc(heap *h, unsigned int size) {
    if (h->current == h->size) {
        collect(h);
    }
    heapPart *part = h->primary + h->current;
    if (part->current + size > part->size) {
        collect(h);
        part = h->primary + h->current;
    }
    void *p = part->data + part->current;
    part->current += size;
    return p;
}

void *reallocate(heap *h, void *p, unsigned int size) {
    if (p == NULL) {
        return alloc(h, size);
    }
    heapPart *part = h->primary;
    unsigned int i;
    for (i = 0; i < h->current; i++) {
        if (p >= part->data && p < part->data + part->size) {
            break;
        }
        part++;
    }
    if (i == h->current) {
        return NULL;
    }
    if (size <= part->size) {
        return p;
    }
    void *newP = alloc(h, size);
    if (newP == NULL) {
        return NULL;
    }
    memcpy(newP, p, part->size);
    return newP;
}