Freecell68k/strntol.c
2019-05-03 21:29:26 -07:00

90 lines
1.4 KiB
C

/*
* Adapted from GCC strtol.c
*/
#include "strntol.h"
#include <limits.h>
#include <ctype.h>
long strntol(const char *nptr, size_t sz, char **endptr, int base) {
const char *s = nptr;
unsigned long acc = 0;
int c;
unsigned long cutoff;
int neg = 0, any = 0, cutlim;
++sz; /* Bounds fix */
/* Skip whitespace, pick up +/- sign, detect prefix. */
do {
c = *s++;
--sz;
} while(isspace(c) && sz > 0);
if(sz == 0) {
goto err;
}
if(c == '-') {
neg = 1;
c = *s++;
sz--;
} else if(c == '+') {
c = *s++;
}
if((base == 0 || base == 16) &&
sz >= 2 && c == '0' && (*s == 'x' || *s == 'X')) {
c = s[1];
s += 2;
sz -= 2;
base = 16;
}
if(base == 0) {
base = c == '0' ? 8 : 10;
}
/* Compute cutoff between legal / illegal numbers */
cutoff = neg ? -(unsigned long) LONG_MIN : LONG_MAX;
cutlim = cutoff % (unsigned long) base;
cutoff /= (unsigned long) base;
for(;; --sz, c = *s++) {
if(sz == 0) {
break;
}
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;
} else if(neg) {
acc = -acc;
}
err:
if(endptr != 0) {
*endptr = (char *) (any ? s - 1 : nptr);
}
return acc;
}