#include "buf.h"

void* buf_grow1(void* v, size_t esize, ptrdiff_t n) {
    struct buf* p;
    size_t max = (size_t)-1 - sizeof(struct buf);
    if (v) {
        p = buf_ptr(v);
        if (n > 0 && p->capacity + n > max / esize)
            goto fail; /* overflow */
        p = realloc(p, sizeof(struct buf) + esize * (p->capacity + n));
        if (!p)
            goto fail;
        p->capacity += n;
        if (p->size > p->capacity)
            p->size = p->capacity;
    } else {
        if ((size_t)n > max / esize)
            goto fail; /* overflow */
        p = malloc(sizeof(struct buf) + esize * n);
        if (!p)
            goto fail;
        p->capacity = n;
        p->size = 0;
    }
    return p->buffer;
fail:
    BUF_ABORT;
    return 0;
}