/* base64.c
 * Base-64 conversion
 *
 * Wireshark - Network traffic analyzer
 * By Gerald Combs <gerald@wireshark.org>
 * Copyright 1998 Gerald Combs
 *
 * SPDX-License-Identifier: GPL-2.0-or-later
 */

#include "config.h"

#include <string.h>
#include "base64.h"

/* Decode a base64 string in-place - simple and slow algorithm.
   Return length of result. Taken from rproxy/librsync/base64.c by
   Andrew Tridgell. */

size_t ws_base64_decode_inplace(char *s)
{
	static const char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/\r\n";
	int bit_offset, byte_offset, idx, i;
	unsigned char *d = (unsigned char *)s;
	char *p;
	int  cr_idx;

	/* we will allow CR and LF - but ignore them */
	cr_idx = (int)(strchr(b64, '\r') - b64);

	i = 0;

	while (*s && (p = strchr(b64, *s))) {
		idx = (int)(p - b64);
		if (idx < cr_idx) {
			byte_offset = (i * 6) / 8;
			bit_offset = (i * 6) % 8;
			d[byte_offset] &= ~((1 << (8 - bit_offset)) - 1);
			if (bit_offset < 3) {
				d[byte_offset] |= (idx << (2 - bit_offset));
			} else {
				d[byte_offset] |= (idx >> (bit_offset - 2));
				d[byte_offset + 1] = 0;
				d[byte_offset + 1] |= (idx << (8 - (bit_offset - 2))) & 0xFF;
			}
			i++;
		}
		s++;
	}

	d[i*3/4] = 0;
	return i*3/4;
}

/*
 * Editor modelines  -  http://www.wireshark.org/tools/modelines.html
 *
 * Local variables:
 * c-basic-offset: 8
 * tab-width: 8
 * indent-tabs-mode: t
 * End:
 *
 * vi: set shiftwidth=8 tabstop=8 noexpandtab:
 * :indentSize=8:tabSize=8:noTabs=false:
 */