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#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <limits.h>
extern int errno;
int get_value(char c, long base) {
int r;
if (c >= '0' && c <= '9')
r = c - '0';
else if (c >= 'A' && c <= 'Z')
r = c - 'A';
else if (c >= 'a' && c <= 'z')
r = c - 'a';
else
return -1;
if (r >= base)
return -1;
return r;
}
// https://pubs.opengroup.org/onlinepubs/9699919799/functions/strtoul.html
unsigned long strtoul(const char *restrict str, char **restrict endptr,
int base) {
unsigned long ret_value = 0;
if (endptr)
*endptr = str;
// Ignore inital white-space sequence
for (; *str && isspace(*str); str++)
;
if (!*str)
return ret_value;
int sign = 0;
if ('-' == *str) {
// FIXME
sign = 1;
str++;
assert(0);
} else if ('+' == *str) {
str++;
}
if (0 == base) {
// FIXME
assert(0);
}
if (2 <= base && 36 >= base) {
for (; *str; str++) {
ret_value *= base;
int val = get_value(*str, base);
/*
if (-1 == val) {
errno = ERANGE;
return 0;
}*/
if (ret_value > ULONG_MAX - val) {
errno = ERANGE;
return 0;
}
ret_value += val;
}
} else {
errno = EINVAL;
return 0;
}
if (endptr)
*endptr = str;
return ret_value;
}
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