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#include <stdlib.h>
#include <limits.h>
#include <errno.h>
long
strtol(const char *nptr, char **endptr, int base)
{
const char *p;
long n, nn;
int c, ovfl, v, neg, ndig;
p = nptr;
neg = 0;
n = 0;
ndig = 0;
ovfl = 0;
/*
* White space
*/
for(;;p++){
switch(*p){
case ' ':
case '\t':
case '\n':
case '\f':
case '\r':
case '\v':
continue;
}
break;
}
/*
* Sign
*/
if(*p=='-' || *p=='+')
if(*p++ == '-')
neg = 1;
/*
* Base
*/
if(base==0){
if(*p != '0')
base = 10;
else{
base = 8;
if(p[1]=='x' || p[1]=='X'){
p += 2;
base = 16;
}
}
}else if(base==16 && *p=='0'){
if(p[1]=='x' || p[1]=='X')
p += 2;
}else if(base<0 || 36<base)
goto Return;
/*
* Non-empty sequence of digits
*/
for(;; p++,ndig++){
c = *p;
v = base;
if('0'<=c && c<='9')
v = c - '0';
else if('a'<=c && c<='z')
v = c - 'a' + 10;
else if('A'<=c && c<='Z')
v = c - 'A' + 10;
if(v >= base)
break;
nn = n*base + v;
if(nn < n)
ovfl = 1;
n = nn;
}
Return:
if(ndig == 0)
p = nptr;
if(endptr)
*endptr = (char *)p;
if(ovfl){
errno = ERANGE;
if(neg)
return LONG_MIN;
return LONG_MAX;
}
if(neg)
return -n;
return n;
}
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