/*
 * Copyright (c) 1999 G. Adam Stanislav
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 *
 *	sget.utf-8.c v.1
 */

#include <stdio.h>

#define	INVALID	0x80000000

#define	get(c)	c = *strptr++; \
	if (chars) (*chars)++; \
	if ((c) == 0) return (unsigned int)EOF

unsigned int sgetu8(unsigned char *strptr, int *chars) {
	unsigned int c;
	int i, iterations;
	unsigned char ch;

	if (chars) *chars = 0;

	if (strptr == NULL)
		return (unsigned int)EOF;

	get(c);

	if ((c & 0xFE) == 0xFC) {
		c &= 0x01;
		iterations = 5;
	}
	else if ((c & 0xFC) == 0xF8) {
		c &= 0x03;
		iterations = 4;
	}
	else if ((c & 0xF8) == 0xF0) {
		c &= 0x07;
		iterations = 3;
	}
	else if ((c & 0xF0) == 0xE0) {
		c &= 0x0F;
		iterations = 2;
	}
	else if ((c & 0xE0) == 0xC0) {
		c &= 0x1F;
		iterations = 1;
	}
	else if ((c & 0x80) == 0x80)
		return INVALID;
	else return c;

	for (i = 0; i < iterations; i++) {
		get(ch);
		if ((ch & 0xC0) != 0x80)
			return INVALID;
		c <<= 6;
		c |= ch & 0x3F;
	}

	return c;
}