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75 lines
1.4 KiB
C
75 lines
1.4 KiB
C
#include <precomp.h>
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#include <ctype.h>
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/*
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* Convert a string to an unsigned long integer.
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*
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* Ignores `locale' stuff. Assumes that the upper and lower case
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* alphabets and digits are each contiguous.
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*
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* @implemented
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*/
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unsigned long
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strtoul(const char *nptr, char **endptr, int base)
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{
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const char *s = nptr;
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unsigned long acc;
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int c;
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unsigned long cutoff;
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int neg = 0, any, cutlim;
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/*
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* See strtol for comments as to the logic used.
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*/
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do {
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c = *s++;
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} while (isspace(c));
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if (c == '-')
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{
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neg = 1;
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c = *s++;
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}
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else if (c == '+')
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c = *s++;
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if ((base == 0 || base == 16) &&
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c == '0' && (*s == 'x' || *s == 'X'))
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{
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c = s[1];
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s += 2;
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base = 16;
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}
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if (base == 0)
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base = c == '0' ? 8 : 10;
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cutoff = (unsigned long)ULONG_MAX / (unsigned long)base;
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cutlim = (unsigned long)ULONG_MAX % (unsigned long)base;
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for (acc = 0, any = 0;; c = *s++)
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{
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if (isdigit(c))
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c -= '0';
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else if (isalpha(c))
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c -= isupper(c) ? 'A' - 10 : 'a' - 10;
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else
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break;
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if (c >= base)
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break;
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if (any < 0 || acc > cutoff || (acc == cutoff && c > cutlim))
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any = -1;
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else {
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any = 1;
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acc *= base;
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acc += c;
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}
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}
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if (any < 0)
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{
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acc = ULONG_MAX;
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#ifndef _LIBCNT_
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_set_errno(ERANGE);
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#endif
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}
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else if (neg)
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acc = 0-acc;
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if (endptr != 0)
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*endptr = any ? (char *)((size_t)(s - 1)) : (char *)((size_t)nptr);
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return acc;
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}
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