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DEFINITIONS
This source file includes following definitions.
- atoi
1 /*
2 * Copyright (c) 2000, 2001, 2002, 2003, 2004, 2005, 2008, 2009
3 * The President and Fellows of Harvard College.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 3. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE UNIVERSITY AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 /*
31 * This file is shared between libc and the kernel, so don't put anything
32 * in here that won't work in both contexts.
33 */
34
35 #ifdef _KERNEL
36 #include <types.h>
37 #include <lib.h>
38 #else
39 #include <stdlib.h>
40 #include <string.h>
41 #endif
42
43 /*
44 * Standard C function: parse a string that represents a decimal integer.
45 * Leading whitespace is allowed. Trailing gunk is allowed too. Doesn't
46 * really report syntax errors or overflow in any useful way.
47 */
48
49 int
50 atoi(const char *s)
51 {
52 static const char digits[] = "0123456789"; /* legal digits in order */
53 unsigned val=0; /* value we're accumulating */
54 int neg=0; /* set to true if we see a minus sign */
55
56 /* skip whitespace */
57 while (*s==' ' || *s=='\t') {
58 s++;
59 }
60
61 /* check for sign */
62 if (*s=='-') {
63 neg=1;
64 s++;
65 }
66 else if (*s=='+') {
67 s++;
68 }
69
70 /* process each digit */
71 while (*s) {
72 const char *where;
73 unsigned digit;
74
75 /* look for the digit in the list of digits */
76 where = strchr(digits, *s);
77 if (where==NULL) {
78 /* not found; not a digit, so stop */
79 break;
80 }
81
82 /* get the index into the digit list, which is the value */
83 digit = (where - digits);
84
85 /* could (should?) check for overflow here */
86
87 /* shift the number over and add in the new digit */
88 val = val*10 + digit;
89
90 /* look at the next character */
91 s++;
92 }
93
94 /* handle negative numbers */
95 if (neg) {
96 return -val;
97 }
98
99 /* done */
100 return val;
101 }