Function ensure

src/cjson.c:450–533

realloc printbuffer if necessary to have at least "needed" bytes more */

/* realloc printbuffer if necessary to have at least "needed" bytes more */
static unsigned char* ensure(printbuffer * const p, size_t needed)
{
    unsigned char *newbuffer = NULL;
    size_t newsize = 0;

    if ((p == NULL) || (p->buffer == NULL))
    {
        return NULL;
    }

    if ((p->length > 0) && (p->offset >= p->length))
    {
        /* make sure that offset is valid */
        return NULL;
    }

    if (needed > SIZE_MAX)
    {
        /* sizes bigger than SIZE_MAX are currently not supported */
        return NULL;
    }

    needed += p->offset + 1;
    if (needed <= p->length)
    {
        return p->buffer + p->offset;
    }

    if (p->noalloc) {
        return NULL;
    }

    /* calculate new buffer size */
    if (needed > (SIZE_MAX / 2))
    {
        /* overflow of int, use SIZE_MAX if possible */
        if (needed <= SIZE_MAX)
        {
            newsize = SIZE_MAX;
        }
        else
        {
            return NULL;
        }
    }
    else
    {
        newsize = needed * 2;
    }

    if (p->hooks.reallocate != NULL)
    {
        /* reallocate with realloc if available */
        newbuffer = (unsigned char*)p->hooks.reallocate(p->buffer, newsize);
        if (newbuffer == NULL)
        {
            p->hooks.deallocate(p->buffer);
            p->length = 0;