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91 lines
2.2 KiB
C
91 lines
2.2 KiB
C
#include <precomp.h>
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/*
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* @implemented
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*/
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long
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strtol(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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* Skip white space and pick up leading +/- sign if any.
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* If base is 0, allow 0x for hex and 0 for octal, else
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* assume decimal; if base is already 16, allow 0x.
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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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/*
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* Compute the cutoff value between legal numbers and illegal
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* numbers. That is the largest legal value, divided by the
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* base. An input number that is greater than this value, if
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* followed by a legal input character, is too big. One that
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* is equal to this value may be valid or not; the limit
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* between valid and invalid numbers is then based on the last
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* digit. For instance, if the range for longs is
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* [-2147483648..2147483647] and the input base is 10,
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* cutoff will be set to 214748364 and cutlim to either
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* 7 (neg==0) or 8 (neg==1), meaning that if we have accumulated
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* a value > 214748364, or equal but the next digit is > 7 (or 8),
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* the number is too big, and we will return a range error.
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*
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* Set any if any `digits' consumed; make it negative to indicate
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* overflow.
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*/
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cutoff = neg ? -(unsigned long)LONG_MIN : LONG_MAX;
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cutlim = cutoff % (unsigned long)base;
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cutoff /= (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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{
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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 = neg ? LONG_MIN : LONG_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 = -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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