90 lines
1.4 KiB
C
90 lines
1.4 KiB
C
/*
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* Adapted from GCC strtol.c
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*/
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#include "strntol.h"
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#include <limits.h>
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#include <ctype.h>
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long strntol(const char *nptr, size_t sz, char **endptr, int base) {
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const char *s = nptr;
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unsigned long acc = 0;
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int c;
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unsigned long cutoff;
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int neg = 0, any = 0, cutlim;
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++sz; /* Bounds fix */
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/* Skip whitespace, pick up +/- sign, detect prefix. */
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do {
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c = *s++;
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--sz;
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} while(isspace(c) && sz > 0);
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if(sz == 0) {
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goto err;
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}
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if(c == '-') {
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neg = 1;
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c = *s++;
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sz--;
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} else if(c == '+') {
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c = *s++;
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}
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if((base == 0 || base == 16) &&
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sz >= 2 && c == '0' && (*s == 'x' || *s == 'X')) {
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c = s[1];
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s += 2;
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sz -= 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 cutoff between legal / illegal numbers */
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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(;; --sz, c = *s++) {
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if(sz == 0) {
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break;
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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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}
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if(c >= base) {
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break;
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}
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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 = neg ? LONG_MIN : LONG_MAX;
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} else if(neg) {
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acc = -acc;
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}
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err:
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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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} |