/* $NetBSD: unicode.c,v 1.3 2015/06/21 14:09:47 maxv Exp $ */

/*-
 * Copyright (c) 2007 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Dieter Baron.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION OR CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: unicode.c,v 1.3 2015/06/21 14:09:47 maxv Exp $");

#include <sys/null.h>

#include "unicode.h"

size_t
utf8_to_utf16(uint16_t *dst, size_t dst_len,
	      const char *src, size_t src_len,
	      int flags, int *errp)
{
	const unsigned char *s;
	size_t spos, dpos;
	int error;
	uint16_t c;

#define IS_CONT(c)	(((c)&0xc0) == 0x80)

	error = 0;
	s = (const unsigned char *)src;
	spos = dpos = 0;
	while (spos < src_len) {
		if (s[spos] < 0x80) {
			c = s[spos++];
		} else if ((flags & UNICODE_UTF8_LATIN1_FALLBACK)
			 && (spos >= src_len || !IS_CONT(s[spos+1]))
			 && s[spos]>=0xa0) {
			/* not valid UTF-8, assume ISO 8859-1 */
			c = s[spos++];
		} else if (s[spos] < 0xc0 || s[spos] >= 0xf5) {
			/* continuation byte without lead byte
			 * or lead byte for codepoint above 0x10ffff */
			error++;
			spos++;
			continue;
		} else if (s[spos] < 0xe0) {
			if (spos >= src_len || !IS_CONT(s[spos+1])) {
				spos++;
				error++;
				continue;
			}
			c = ((s[spos] & 0x3f) << 6) | (s[spos+1] & 0x3f);
			spos += 2;
			if (c < 0x80) {
				/* overlong encoding */
				error++;
				continue;
			}
		} else if (s[spos] < 0xf0) {
			if (spos >= src_len-2 ||
			    !IS_CONT(s[spos+1]) || !IS_CONT(s[spos+2])) {
				spos++;
				error++;
				continue;
			}
			c = ((s[spos] & 0x0f) << 12) | ((s[spos+1] & 0x3f) << 6)
			    | (s[spos+2] & 0x3f);
			spos += 3;
			if (c < 0x800 || (c & 0xdf00) == 0xd800 ) {
				/* overlong encoding or encoded surrogate */
				error++;
				continue;
			}
		} else {
			uint32_t cc;
			/* UTF-16 surrogate pair */

			if (spos >= src_len-3 || !IS_CONT(s[spos+1])
			    || !IS_CONT(s[spos+2]) || !IS_CONT(s[spos+3])) {
				spos++;
				error++;
				continue;
			}
			cc = ((s[spos] & 0x03) << 18) | ((s[spos+1] & 0x3f) << 12)
			    | ((s[spos+2] & 0x3f) << 6) | (s[spos+3] & 0x3f);
			spos += 4;
			if (cc < 0x10000) {
				/* overlong encoding */
				error++;
				continue;
			}
			if (dst && dpos < dst_len)
				dst[dpos] = (0xd800 | ((cc-0x10000)>>10));
			dpos++;
			c = 0xdc00 | ((cc-0x10000) & 0x3ffff);
		}

		if (dst && dpos < dst_len)
			dst[dpos] = c;
		dpos++;
	}

	if (errp)
		*errp = error;
	return dpos;
#undef IS_CONT
}


size_t
utf16_to_utf8(char *dst, size_t dst_len,
	      const uint16_t *src, size_t src_len,
	      int flags, int *errp)
{
	uint8_t spos, dpos;
	int error;

#define CHECK_LENGTH(l)	(dpos > dst_len-(l) ? dst=NULL : NULL)
#define ADD_BYTE(b)	(dst ? dst[dpos] = (b) : 0, dpos++)

	error = 0;
	dpos = 0;
	for (spos = 0; spos < src_len; spos++) {
		if (src[spos] < 0x80) {
			CHECK_LENGTH(1);
			ADD_BYTE(src[spos]);
		} else if (src[spos] < 0x800) {
			CHECK_LENGTH(2);
			ADD_BYTE(0xc0 | (src[spos]>>6));
			ADD_BYTE(0x80 | (src[spos] & 0x3f));
		} else if ((src[spos] & 0xdc00) == 0xd800) {
			uint32_t c;
			/* first surrogate */
			if (spos == src_len - 1 || (src[spos] & 0xdc00) != 0xdc00) {
				/* no second surrogate present */
				error++;
				continue;
			}
			spos++;
			CHECK_LENGTH(4);
			c = (((src[spos]&0x3ff) << 10) | (src[spos+1]&0x3ff)) + 0x10000;
			ADD_BYTE(0xf0 | (c>>18));
			ADD_BYTE(0x80 | ((c>>12) & 0x3f));
			ADD_BYTE(0x80 | ((c>>6) & 0x3f));
			ADD_BYTE(0x80 | (c & 0x3f));
		} else if ((src[spos] & 0xdc00) == 0xdc00) {
			/* second surrogate without preceding first surrogate */
			error++;
		} else {
			CHECK_LENGTH(3);
			ADD_BYTE(0xe0 | src[spos]>>12);
			ADD_BYTE(0x80 | ((src[spos]>>6) & 0x3f));
			ADD_BYTE(0x80 | (src[spos] & 0x3f));
		}
	}

	if (errp)
		*errp = error;
	return dpos;
#undef ADD_BYTE
#undef CHECK_LENGTH
}