/* *****************************************************************************
 * utils/skip.c -- skip some bytes (useful for debugging).
 * Copyright (C) 2017 Thomas "Cakeisalie5" Touhey <thomas@touhey.fr>
 *
 * This file is part of libg1m.
 * libg1m is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3.0 of the License,
 * or (at your option) any later version.
 *
 * libg1m is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with libg1m; if not, see <http://www.gnu.org/licenses/>.
 * ************************************************************************** */
#include <libg1m/internals.h>

/**
 *	g1m_skip:
 *	Skip some bytes.
 *
 *	@arg	buffer		the buffer from which to read.
 *	@arg	size		the size to skip.
 *	@arg	checksum	pointer to the checksum variable if there is one.
 */

int g1m_skip(g1m_buffer_t *buffer, size_t size, uint32_t *checksum)
{
	uint8_t buf[1024]; int err;
	uint32_t add = 0;
#if LOGLEVEL <= ll_error
	size_t orig = size;
#endif

	while (size) {
		/* read that much */
		size_t curlen = min(size, 1024);
		size -= curlen;
		buffer->g1m_buffer_offset += curlen;
		if ((err = (*buffer->g1m_buffer_read)(buffer->g1m_buffer_cookie, buf,
		  curlen))) {
			log_error("Skipping has failed after %" PRIuSIZE " bytes",
				orig - size);
			return (err);
		}

		/* feed the checksum */
		add = g1m_checksum32(buf, curlen, add);
	}

	/* add to checksum */
	if (checksum) *checksum += add;

	/* no error */
	return (0);
}