long atol(const char *nptr)
{
int c; /* current char */
long total; /* current total */
int sign; /* if ''-'', then negative, otherwise positive */
/* skip whitespace */
while ( isspace((int)(unsigned char)*nptr) )
++nptr;
c = (int)(unsigned char)*nptr++;
sign = c;
if (c == ''-'' || c == ''+'')
c = (int)(unsigned char)*nptr++;
total = 0;
while (isdigit(c)) {
total = 10 * total + (c - ''0''); /* accumulate digit */
c = (int)(unsigned char)*nptr++; /* get next char */
}
if (sign == ''-'')
return -total;
else
return total; /* return result, negated if necessary */
}
char* _itoa(int value, char* string, int radix)
{
char tmp[33];
char* tp = tmp;
int i;
unsigned v;
int sign;
char* sp;
if (radix > 36 || radix <= 1)
{
__set_errno(EDOM);
return 0;
}
sign = (radix == 10 && value < 0);
if (sign)
v = -value;
else
v = (unsigned)value;
while (v || tp == tmp)
{
i = v % radix;
v = v / radix;
if (i < 10)
*tp++ = i+''0'';
else
*tp++ = i + ''a'' - 10;
}
if (string == 0)
string = (char*)malloc((tp-tmp)+sign+1);
sp = string;
if (sign)
*sp++ = ''-'';
while (tp > tmp)
*sp++ = *--tp;
*sp = 0;
return string;
}
转载于:https://www.cnblogs.com/caleb/archive/2011/09/13/2174967.html