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strtoul.c
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1995-03-23
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4KB
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111 lines
/*
* Program: String to unsigned long
*
* Author: Mark Crispin
* Networks and Distributed Computing
* Computing & Communications
* University of Washington
* Administration Building, AG-44
* Seattle, WA 98195
*
* Date: 14 February 1995
* Last Edited: 23 March 1995
*
* Copyright 1995 by the University of Washington
*
* Permission to use, copy, modify, and distribute this software and its
* documentation for any purpose and without fee is hereby granted, provided
* that the above copyright notice appears in all copies and that both the
* above copyright notice and this permission notice appear in supporting
* documentation, and that the name of the University of Washington not be
* used in advertising or publicity pertaining to distribution of the software
* without specific, written prior permission. This software is made
* available "as is", and
* THE UNIVERSITY OF WASHINGTON DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
* WITH REGARD TO THIS SOFTWARE, INCLUDING WITHOUT LIMITATION ALL IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, AND IN
* NO EVENT SHALL THE UNIVERSITY OF WASHINGTON BE LIABLE FOR ANY SPECIAL,
* INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, TORT
* (INCLUDING NEGLIGENCE) OR STRICT LIABILITY, ARISING OUT OF OR IN CONNECTION
* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
*/
/*
* Turn a string unsigned long into the real thing
* Accepts: source string
* pointer to place to return end pointer
* base
* Returns: parsed unsigned long integer, end pointer is updated
*/
unsigned long strtoul (char *s,char **endp,int base)
{
unsigned long value = 0; /* the accumulated value */
/* Yes, you can feed it negative number strings */
int negative = 0; /* this a negative number? */
int ok; /* true while valid chars for number */
char c;
if (base && (base < 2 || base > 36)) {
errno = EINVAL; /* insist upon valid base */
return NIL;
}
while (isspace (*s)) s++; /* skip leading whitespace */
if (base) { /* if have a base */
switch (*s) { /* check for leading sign char */
case '-':
negative = 1; /* yes, negative #. fall into '+' */
case '+':
s++; /* skip the sign character */
}
/* allow hex prefix "0x" */
if (base == 16 && *s == '0' && toupper (*(s + 1)) == 'X') s += 2;
do { /* convert to numeric form if digit*/
if (isdigit (*s)) c = toint (*s);
/* alphabetic conversion */
else if (isalpha (*s)) c = *s - (isupper (*s) ? 'A' : 'a') + 10;
else break; /* else no way it's valid */
if (c >= base) break; /* digit out of range for base? */
value = value * base + c; /* accumulate the digit */
} while (*++s); /* loop until non-numeric character */
}
else { /* if base = 0, */
if (*s == '-') { /* integer constants are allowed a */
negative = 1; /* leading unary minus, but not */
s++; /* unary plus. */
}
if (*s == '0') { /* if it starts with 0, its either */
if (toupper (*++s)=='X') {/* 0X, which marks a hex constant, */
s++; /* skip the X */
base = 16; /* base is hex 16 */
}
else base = 8; /* leading 0 means octal number */
}
else base = 10; /* otherwise, decimal. */
do {
switch (base) { /* char has to be valid for base */
case 8: /* this digit ok? */
ok = isodigit (*s);
break;
case 10:
ok = isdigit (*s);
break;
case 16:
ok = isxdigit (*s);
break;
default: /* it's good form you know */
return NIL;
}
/* if valid char, accumulate */
if (ok) value = value * base + toint (*s++);
} while (ok);
if (toupper (*s) == 'L')s++;/* ignore 'l' or 'L' marker */
}
if (endp) *endp = s; /* save users endp to after number */
/* negate number if needed */
return (negative) ? -value : value;
}