75 lines
1.5 KiB
C
75 lines
1.5 KiB
C
#include <ctype.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <limits.h>
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unsigned long 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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do {
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c = *s++;
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} while (isspace(c));
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if (c == '-') {
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neg = 1;
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c = *s++;
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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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c = s[1];
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s += 2;
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base = 16;
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} else if ((base == 0 || base == 2) &&
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c == '0' && (*s == 'b' || *s == 'B')) {
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c = s[1];
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s += 2;
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base = 2;
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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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cutoff = ULONG_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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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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}
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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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acc = ULONG_MAX;
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} else if (neg) {
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acc = -acc;
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}
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if (endptr != 0) {
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*endptr = (char *)(any ? s - 1 : nptr);
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}
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return acc;
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}
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