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strtoul.c
< prev
Wrap
C/C++ Source or Header
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1995-04-27
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3KB
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169 lines
#include <stdio.h> /* For NULL */
/* strtol.c */
#include <ctype.h>
#include <errno.h>
/* #include <limits.h> */
#define UNSIGNED 1
#ifndef ULONG_MAX
#define LONG_MAX (~(1 << (sizeof (long) * 8 - 1)))
#define LONG_MIN (-LONG_MAX-1)
#define ULONG_MAX ((unsigned long) ~(unsigned long) 0)
#endif
#ifndef NULL
#define NULL 0
#endif
extern int errno;
#if !defined(__STDC__)
#define const
#endif
#ifndef UNSIGNED
#define UNSIGNED 0
#endif
/* Convert NPTR to an `unsigned long int' or `long int' in base BASE.
If BASE is 0 the base is determined by the presence of a leading
zero, indicating octal or a leading "0x" or "0X", indicating hexadecimal.
If BASE is < 2 or > 36, it is reset to 10.
If ENDPTR is not NULL, a pointer to the character after the last
one converted is stored in *ENDPTR. */
#if UNSIGNED
unsigned long
#define strtol strtoul
#else
long int
#endif
strtol (nptr, endptr, base)
const char *nptr;
char **endptr;
int base;
{
int negative;
register unsigned long int cutoff;
register unsigned int cutlim;
register unsigned long int i;
register const char *s;
register unsigned char c;
const char *save;
int overflow;
if (base < 0 || base == 1 || base > 36)
base = 10;
s = nptr;
/* Skip white space. */
while (isspace (*s))
++s;
if (*s == '\0')
goto noconv;
/* Check for a sign. */
if (*s == '-')
{
negative = 1;
++s;
}
else if (*s == '+')
{
negative = 0;
++s;
}
else
negative = 0;
if (base == 16 && s[0] == '0' && toupper (s[1]) == 'X')
s += 2;
/* If BASE is zero, figure it out ourselves. */
if (base == 0)
{
if (*s == '0')
{
if (toupper (s[1]) == 'X')
{
s += 2;
base = 16;
}
else
base = 8;
}
else
base = 10;
}
/* Save the pointer so we can check later if anything happened. */
save = s;
cutoff = ULONG_MAX / (unsigned long int) base;
cutlim = ULONG_MAX % (unsigned long int) base;
overflow = 0;
i = 0;
for (c = *s; c != '\0'; c = *++s)
{
if (isdigit (c))
c -= '0';
else if (isalpha (c))
c = toupper (c) - 'A' + 10;
else
break;
if (c >= base)
break;
/* Check for overflow. */
if (i > cutoff || (i == cutoff && c > cutlim))
overflow = 1;
else
{
i *= (unsigned long int) base;
i += c;
}
}
/* Check if anything actually happened. */
if (s == save)
goto noconv;
/* Store in ENDPTR the address of one character
past the last character we converted. */
if (endptr != NULL)
*endptr = (char *) s;
#if !UNSIGNED
/* Check for a value that is within the range of
`unsigned long int', but outside the range of `long int'. */
if (i > (negative ?
- (unsigned long int) LONG_MIN : (unsigned long int) LONG_MAX))
overflow = 1;
#endif
if (overflow)
{
errno = ERANGE;
#if UNSIGNED
return ULONG_MAX;
#else
return negative ? LONG_MIN : LONG_MAX;
#endif
}
/* Return the result of the appropriate sign. */
return (negative ? - i : i);
noconv:;
/* There was no number to convert. */
if (endptr != NULL)
*endptr = (char *) nptr;
return 0L;
}