xref: /illumos-gate/usr/src/lib/libc/port/gen/atoi.c (revision 59d65d3175825093531e82f44269d948ed510a00)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1988 AT&T	*/
28 /*	  All Rights Reserved  	*/
29 
30 #include "lint.h"
31 #include <ctype.h>
32 #include <sys/types.h>
33 #include <stdlib.h>
34 
35 #define	ATOI
36 
37 #ifdef	ATOI
38 typedef int TYPE;
39 #define	NAME	atoi
40 #else
41 typedef long TYPE;
42 #define	NAME	atol
43 #endif
44 
45 TYPE
46 NAME(const char *p)
47 {
48 	TYPE n;
49 	int c, neg = 0;
50 	unsigned char	*up = (unsigned char *)p;
51 
52 	if (!isdigit(c = *up)) {
53 		while (isspace(c))
54 			c = *++up;
55 		switch (c) {
56 		case '-':
57 			neg++;
58 			/* FALLTHROUGH */
59 		case '+':
60 			c = *++up;
61 		}
62 		if (!isdigit(c))
63 			return (0);
64 	}
65 	for (n = '0' - c; isdigit(c = *++up); ) {
66 		n *= 10; /* two steps to avoid unnecessary overflow */
67 		n += '0' - c; /* accum neg to avoid surprises at MAX */
68 	}
69 	return (neg ? n : -n);
70 }
71