1 /*-
2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 */
7
8 #if defined(LIBC_SCCS) && !defined(lint)
9 static char sccsid[] = "@(#)strtol.c 8.1 (Berkeley) 06/04/93";
10 #endif /* LIBC_SCCS and not lint */
11
12 #include <limits.h>
13 #include <ctype.h>
14 #include <errno.h>
15 #include <stdlib.h>
16
17
18 /*
19 * Convert a string to a long integer.
20 *
21 * Ignores `locale' stuff. Assumes that the upper and lower case
22 * alphabets and digits are each contiguous.
23 */
24 long
strtol(nptr,endptr,base)25 strtol(nptr, endptr, base)
26 const char *nptr;
27 char **endptr;
28 register int base;
29 {
30 register const char *s = nptr;
31 register unsigned long acc;
32 register int c;
33 register unsigned long cutoff;
34 register int neg = 0, any, cutlim;
35
36 /*
37 * Skip white space and pick up leading +/- sign if any.
38 * If base is 0, allow 0x for hex and 0 for octal, else
39 * assume decimal; if base is already 16, allow 0x.
40 */
41 do {
42 c = *s++;
43 } while (isspace(c));
44 if (c == '-') {
45 neg = 1;
46 c = *s++;
47 } else if (c == '+')
48 c = *s++;
49 if ((base == 0 || base == 16) &&
50 c == '0' && (*s == 'x' || *s == 'X')) {
51 c = s[1];
52 s += 2;
53 base = 16;
54 }
55 if (base == 0)
56 base = c == '0' ? 8 : 10;
57
58 /*
59 * Compute the cutoff value between legal numbers and illegal
60 * numbers. That is the largest legal value, divided by the
61 * base. An input number that is greater than this value, if
62 * followed by a legal input character, is too big. One that
63 * is equal to this value may be valid or not; the limit
64 * between valid and invalid numbers is then based on the last
65 * digit. For instance, if the range for longs is
66 * [-2147483648..2147483647] and the input base is 10,
67 * cutoff will be set to 214748364 and cutlim to either
68 * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
69 * a value > 214748364, or equal but the next digit is > 7 (or 8),
70 * the number is too big, and we will return a range error.
71 *
72 * Set any if any `digits' consumed; make it negative to indicate
73 * overflow.
74 */
75 cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
76 cutlim = cutoff % (unsigned long)base;
77 cutoff /= (unsigned long)base;
78 for (acc = 0, any = 0;; c = *s++) {
79 if (isdigit(c))
80 c -= '0';
81 else if (isalpha(c))
82 c -= isupper(c) ? 'A' - 10 : 'a' - 10;
83 else
84 break;
85 if (c >= base)
86 break;
87 if (any < 0 || acc > cutoff || acc == cutoff && c > cutlim)
88 any = -1;
89 else {
90 any = 1;
91 acc *= base;
92 acc += c;
93 }
94 }
95 if (any < 0) {
96 acc = neg ? LONG_MIN : LONG_MAX;
97 errno = ERANGE;
98 } else if (neg)
99 acc = -acc;
100 if (endptr != 0)
101 *endptr = (char *)(any ? s - 1 : nptr);
102 return (acc);
103 }
104