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adds handling if we have unallocated buffer

/*************************************************************************
* (C) 2025 AITNET ltd - Sofia/Bulgaria - <misho@aitnet.org>
*  by Michael Pounov <misho@elwix.org>
*
* $Author: misho $
* $Id: ring.c,v 1.1.2.2 2025/09/26 09:22:24 misho Exp $
*
**************************************************************************
The ELWIX and AITNET software is distributed under the following
terms:

All of the documentation and software included in the ELWIX and AITNET
Releases is copyrighted by ELWIX - Sofia/Bulgaria <info@elwix.org>

Copyright 2004 - 2025
	by Michael Pounov <misho@elwix.org>.  All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
1. Redistributions of source code must retain the above copyright
   notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright
   notice, this list of conditions and the following disclaimer in the
   documentation and/or other materials provided with the distribution.
3. All advertising materials mentioning features or use of this software
   must display the following acknowledgement:
This product includes software developed by Michael Pounov <misho@elwix.org>
ELWIX - Embedded LightWeight unIX and its contributors.
4. Neither the name of AITNET nor the names of its contributors
   may be used to endorse or promote products derived from this software
   without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY AITNET AND CONTRIBUTORS ``AS IS'' AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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*/
#include "global.h"


/*
 * rbuf_init() - Init ring buffer
 *
 * @rbuf = Ring buffer
 * @num = Number of elements in buffer
 * return: -1 error or 0 ok
 */
int
rbuf_init(ringbuf_t *rbuf, int num)
{
	if (!rbuf)
		return -1;

	atomic_store_explicit(&rbuf->rb_head, 0, memory_order_relaxed);
	atomic_store_explicit(&rbuf->rb_tail, 0, memory_order_relaxed);

	rbuf->rb_buffer = e_calloc(num, sizeof(struct iovec));
	if (!rbuf->rb_buffer)
		return -1;
	else
		rbuf->rb_bufnum = num;
	memset(rbuf->rb_buffer, 0, num * sizeof(struct iovec));

	return 0;
}

/*
 * rbuf_free() - Free ring buffer
 *
 * @rbuf = Ring buffer
 * return: none
 */
void
rbuf_free(ringbuf_t *rbuf)
{
	if (!rbuf)
		return;

	if (rbuf->rb_buffer) {
		e_free(rbuf->rb_buffer);
		rbuf->rb_buffer = NULL;
		rbuf->rb_bufnum = 0;
	}

	atomic_store_explicit(&rbuf->rb_head, 0, memory_order_relaxed);
	atomic_store_explicit(&rbuf->rb_tail, 0, memory_order_relaxed);
}

/*
 * rbuf_purge() - Purge all buffer
 *
 * @rbuf = Ring buffer
 * return: none
 */
void
rbuf_purge(ringbuf_t *rbuf)
{
	if (!rbuf)
		return;

	if (rbuf->rb_buffer)
		memset(rbuf->rb_buffer, 0, rbuf->rb_bufnum * sizeof(struct iovec));

	atomic_store_explicit(&rbuf->rb_head, 0, memory_order_relaxed);
	atomic_store_explicit(&rbuf->rb_tail, 0, memory_order_relaxed);
}

/*
 * rbuf_isempty() - Check buffer is empty
 *
 * @rbuf = Ring buffer
 * return: -1 error, 0 it isn't empty
 */
int
rbuf_isempty(ringbuf_t *rbuf)
{
	if (!rbuf)
		return -1;

	return (atomic_load_explicit(&rbuf->rb_head, memory_order_acquire) ==
		atomic_load_explicit(&rbuf->rb_tail, memory_order_acquire));
}

/*
 * rbuf_isfull() - Check buffer is full
 *
 * @rbuf = Ring buffer
 * return: -1 error or 0 it isn't full
 */
int
rbuf_isfull(ringbuf_t *rbuf)
{
	if (!rbuf)
		return -1;
	if (!rbuf->rb_bufnum)
		return 1;

	return (((atomic_load_explicit(&rbuf->rb_head, memory_order_relaxed) + 1) % rbuf->rb_bufnum) ==
		atomic_load_explicit(&rbuf->rb_tail, memory_order_acquire));
}

/*
 * rbuf_enqueue() - Enqueue data to buffer
 *
 * @rbuf = Ring buffer
 * @data = Data
 * @len = Length
 * return: -1 error, 1 buffer is full or 0 ok
 */
int
rbuf_enqueue(ringbuf_t *rbuf, void *data, size_t len)
{
	int h, t, n;
	struct iovec *iov;

	if (!rbuf)
		return -1;

	h = atomic_load_explicit(&rbuf->rb_head, memory_order_relaxed);
	t = atomic_load_explicit(&rbuf->rb_tail, memory_order_acquire);
	n = (h + 1) % rbuf->rb_bufnum;

	if (n == t)
		return 1;

	iov = rbuf->rb_buffer + h;
	iov->iov_len = len;
	iov->iov_base = data;

	atomic_store_explicit(&rbuf->rb_head, n, memory_order_release);
	return 0;
}

/*
 * rbuf_dequeue() - Dequeue data from buffer
 *
 * @rbuf = Ring buffer
 * @out = Data, if =NULL, just dequeue data
 * return: -1 error, 1 buffer is empty or 0 ok
 */
int
rbuf_dequeue(ringbuf_t *rbuf, struct iovec *out)
{
	int h, t, n;

	if (!rbuf)
		return -1;

	h = atomic_load_explicit(&rbuf->rb_head, memory_order_acquire);
	t = atomic_load_explicit(&rbuf->rb_tail, memory_order_relaxed);
	n = (t + 1) % rbuf->rb_bufnum;

	if (h == t)
		return 1;

	if (out)
		out = rbuf->rb_buffer + t;

	atomic_store_explicit(&rbuf->rb_tail, n, memory_order_release);
	return 0;
}