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Diffstat (limited to 'missing/strtol.c')
| -rw-r--r-- | missing/strtol.c | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/missing/strtol.c b/missing/strtol.c new file mode 100644 index 00000000..e102ae34 --- /dev/null +++ b/missing/strtol.c @@ -0,0 +1,120 @@ +/* +Article 4291 of comp.lang.c: +From: chris@mimsy.umd.edu (Chris Torek) +Newsgroups: comp.lang.c +Subject: Re: error checking strtol +Message-ID: <24445@mimsy.umd.edu> +Date: 17 May 90 09:31:17 GMT +Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742 + +The following is a working strtol. It depends only on the existence of +correct header files (including <limits.h>) and on ASCII (IBM programmers +will have to use strchr()). It does not support locales other than `C'. +System V programmers should be able to replace their current strtol with +this one. (After writing this, I checked the SVR2 source; it did not +handle several cases correctly.) +*/ + +#ifdef __STDC__ +#include <limits.h> +#else +#define LONG_MIN (-0x80000000) /* for 32-bit 2s-complement at least */ +#define LONG_MAX 0x7fffffff +#endif + +#if 0 +#include <limits.h> +#include <ctype.h> +#include <errno.h> +#endif + +#ifndef _MSC_VER +int errno; +#endif + +/* + * Convert a string to a long integer. + * + * Ignores `locale' stuff. Assumes that the upper and lower case + * alphabets and digits are each contiguous. + */ +long +strtol(nptr, endptr, base) + const char *nptr; + char **endptr; + register int base; +{ + register const char *s = nptr; + register unsigned long acc; + register int c; + register unsigned long cutoff; + register int neg = 0, any, cutlim; + + /* + * Skip white space and pick up leading +/- sign if any. + * If base is 0, allow 0x for hex and 0 for octal, else + * assume decimal; if base is already 16, allow 0x. + */ + do { + c = *s++; + } while (isspace(c)); + if (c == '-') { + neg = 1; + c = *s++; + } else if (c == '+') + c = *s++; + if ((base == 0 || base == 16) && + c == '0' && (*s == 'x' || *s == 'X')) { + c = s[1]; + s += 2; + base = 16; + } + if (base == 0) + base = c == '0' ? 8 : 10; + + /* + * Compute the cutoff value between legal numbers and illegal + * numbers. That is the largest legal value, divided by the + * base. An input number that is greater than this value, if + * followed by a legal input character, is too big. One that + * is equal to this value may be valid or not; the limit + * between valid and invalid numbers is then based on the last + * digit. For instance, if the range for longs is + * [-2147483648..2147483647] and the input base is 10, + * cutoff will be set to 214748364 and cutlim to either + * 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated + * a value > 214748364, or equal but the next digit is > 7 (or 8), + * the number is too big, and we will return a range error. + * + * Set any if any `digits' consumed; make it negative to indicate + * overflow. + */ + cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX; + cutlim = cutoff % (unsigned long)base; + cutoff /= (unsigned long)base; + for (acc = 0, any = 0;; c = *s++) { + if (isdigit(c)) + c -= '0'; + else if (isalpha(c)) + c -= isupper(c) ? 'A' - 10 : 'a' - 10; + else + break; + if (c >= base) + break; + if (any < 0 || acc > cutoff || acc == cutoff && c > cutlim) + any = -1; + else { + any = 1; + acc *= base; + acc += c; + } + } + if (any < 0) { + acc = neg ? LONG_MIN : LONG_MAX; + errno = ERANGE; + } else if (neg) + acc = -acc; + if (endptr != 0) + *endptr = (char *) (any ? s - 1 : nptr); + return (acc); +} |