/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1990, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Copyright (c) 2011 The FreeBSD Foundation
 * All rights reserved.
 * Portions of this software were developed by David Chisnall
 * under sponsorship from the FreeBSD Foundation.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * 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. Neither the name of the University 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 THE REGENTS 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
 * 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 <ctype.h>
#include <stdlib.h>
#include <stdio.h>
#include "shgetc.h"
#include "stdio_impl.h"

int parsefloat(FILE *f, char *buf, char *end)
{
	char *commit, *p;
	int infnanpos = 0, decptpos = 0;
	enum {
		S_START, S_GOTSIGN, S_INF, S_NAN, S_DONE, S_MAYBEHEX,
		S_DIGITS, S_DECPT, S_FRAC, S_EXP, S_EXPDIGITS
	} state = S_START;
	unsigned char c;
	int gotmantdig = 0, ishex = 0;
	const char *decpt = "";

	/*
	 * We set commit = p whenever the string we have read so far
	 * constitutes a valid representation of a floating point
	 * number by itself.  At some point, the parse will complete
	 * or fail, and we will ungetc() back to the last commit point.
	 * To ensure that the file offset gets updated properly, it is
	 * always necessary to read at least one character that doesn't
	 * match; thus, we can't short-circuit "infinity" or "nan(...)".
	 */
	commit = buf - 1;
	for (p = buf; p < end; ) {
		// When file buffer has no content to read, it need to refill buf again.
		if (shgetc(f) < 0) {
			break;
		} else {
			shunget(f);
		}
		c = *f->rpos;
reswitch:
		switch (state) {
		case S_START:
			state = S_GOTSIGN;
			if (c == '-' || c == '+')
				break;
			else
				goto reswitch;
		case S_GOTSIGN:
			switch (c) {
			case '0':
				state = S_MAYBEHEX;
				commit = p;
				break;
			case 'I':
			case 'i':
				state = S_INF;
				break;
			case 'N':
			case 'n':
				state = S_NAN;
				break;
			default:
				state = S_DIGITS;
				goto reswitch;
			}
			break;
		case S_INF:
			if (infnanpos > 6 ||
			    (c != "nfinity"[infnanpos] &&
			     c != "NFINITY"[infnanpos]))
				goto parsedone;
			if (infnanpos == 1 || infnanpos == 6)
				commit = p;	/* inf or infinity */
			infnanpos++;
			break;
		case S_NAN:
			switch (infnanpos) {
			case 0:
				if (c != 'A' && c != 'a')
					goto parsedone;
				break;
			case 1:
				if (c != 'N' && c != 'n')
					goto parsedone;
				else
					commit = p;
				break;
			case 2:
				if (c != '(')
					goto parsedone;
				break;
			default:
				if (c == ')') {
					commit = p;
					infnanpos = -2;
				} else if (!isalnum(c) && c != '_')
					goto parsedone;
				break;
			}
			infnanpos++;
			break;
		case S_DONE:
			goto parsedone;
		case S_MAYBEHEX:
			state = S_DIGITS;
			if (c == 'X' || c == 'x') {
				ishex = 1;
				break;
			} else {	/* we saw a '0', but no 'x' */
				gotmantdig = 1;
				goto reswitch;
			}
		case S_DIGITS:
			if ((ishex && isxdigit(c)) || isdigit(c)) {
				gotmantdig = 1;
			} else {
				state = S_FRAC;
				if (c != '.')
					goto reswitch;
			}
			if (gotmantdig)
				commit = p;
			break;
		case S_DECPT:
			if (c == decpt[decptpos]) {
				if (decpt[++decptpos] == '\0') {
					/* We read the complete decpt seq. */
					state = S_FRAC;
					if (gotmantdig)
						commit = p;
				}
				break;
			} else if (!decptpos) {
				/* We didn't read any decpt characters. */
				state = S_FRAC;
				goto reswitch;
			} else {
				/*
				 * We read part of a multibyte decimal point,
				 * but the rest is invalid, so bail.
				 */
				goto parsedone;
			}
		case S_FRAC:
			if (((c == 'E' || c == 'e') && !ishex) ||
			    ((c == 'P' || c == 'p') && ishex)) {
				if (!gotmantdig)
					goto parsedone;
				else
					state = S_EXP;
			} else if ((ishex && isxdigit(c)) || isdigit(c)) {
				commit = p;
				gotmantdig = 1;
			} else
				goto parsedone;
			break;
		case S_EXP:
			state = S_EXPDIGITS;
			if (c == '-' || c == '+')
				break;
			else
				goto reswitch;
		case S_EXPDIGITS:
			if (isdigit(c))
				commit = p;
			else
				goto parsedone;
			break;
		default:
			abort();
		}
		*p++ = c;
		// When file buffer has no content to read, it need to refill buf again.
		if (shgetc(f) < 0) {
			break;
		} else {
			shunget(f);
		}
		f->rpos++;
	}

parsedone:
	while (commit < --p)
                shunget(f);
	*++commit = '\0';
	return (commit - buf);
}