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| From | Ian Collins <ian-news@hotmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Code for strtol/strtoul |
| Date | 2015-03-25 19:18 +1300 |
| Message-ID | <cnf29uFlek5U2@mid.individual.net> (permalink) |
| References | <mejjh4$i17$1@speranza.aioe.org> <3ugPw.110758$Ak4.1277@fx03.iad> <kfnegodel4j.fsf@x-alumni2.alumni.caltech.edu> <metiiu$6gj$1@speranza.aioe.org> |
jacob navia wrote:
> Le 25/03/2015 05:50, Tim Rentsch a écrit :
>>> Excellent readability. Full points for the comments.
>> I find this response astonishing. The central function
>> is 179 lines long. Any benefit from the content of the
>> comments is more than lost in the maze of the long
>> function body.
>
> Given the specs, can you make it any shorter?
>
> It is easy to say "Too long". But what would you take out?
I'll show you what I came up with. It may not be shorter, but it is
broken down into discrete functions. It also implements all four
conversion functions:
#include <stdlib.h>
#include <errno.h>
#include <ctype.h>
#include <stdbool.h>
#include <limits.h>
static int
convertDigit( char digit, int base )
{
if( base < 11 )
{
return digit - '0';
}
else
{
return digit <= '9' ? digit - '0' : (tolower(digit) - 'a')+10;
}
}
static bool
isValidDigitForBase( char digit, int base )
{
static const char beforeNumber = '0'-1;
static const char afterNumber = '9'+1;
if( base < 11 )
{
return digit > beforeNumber && digit < '0'+base;
}
else
{
const bool isNumber = digit > beforeNumber && digit < afterNumber;
if( isNumber )
{
return true;
}
digit = tolower(digit);
return (digit >= 'a' && (digit - 'a') < base-10);
}
}
static bool
checkPreconditions( const char* str, int base )
{
return (str && (base == 0 || (base > 1 && base < 37)));
}
typedef const char* restrict rp;
static void
checkForAndConsumeHexPrefix( rp* str, int base )
{
if( base == 16 )
{
rp p = *str;
if( *p == '0' && tolower(*(p+1)) == 'x' )
{
*str += 2;
}
}
}
static void
checkForAndConsumeSign( rp* str, bool* isNegative )
{
const char c = **str;
if( c == '-' || c == '+')
{
++*str;
}
*isNegative = (c == '-') ? true : false;
}
static unsigned long long
Strtoull( const char* restrict str,
char** restrict endptr,
int base,
bool* isNegative )
{
if( !checkPreconditions( str, base ) )
{
errno = EINVAL;
return 0;
}
if( endptr ) *endptr = (char*)str;
base = (base == 0) ? 10 : base;
while( isspace(*str) ) ++str;
checkForAndConsumeSign( &str, isNegative );
checkForAndConsumeHexPrefix( &str, base );
unsigned long long result = 0;
while( isValidDigitForBase( *str, base) )
{
const int digit = convertDigit( *str++, base );
if( endptr ) *endptr = (char*)str;
const unsigned long long nextResult = result*base+digit;
if( nextResult < result )
{
errno = ERANGE;
return ULLONG_MAX;
}
result = nextResult;
}
return result;
}
static long long
rangeCheck( unsigned long long result, long long min, long long max,
bool neg )
{
if( neg )
{
const unsigned long long threshold = (unsigned long long)min*-1;
if( result > threshold )
{
errno = ERANGE;
return min;
}
return -result;
}
else
{
if( result > max )
{
errno = ERANGE;
return max;
}
return result;
}
}
unsigned long long
strtoull( const char* restrict str, char** restrict endptr, int base )
{
bool neg = false;
return Strtoull( str, endptr, base, &neg );
}
long long
strtoll( const char* restrict str, char** restrict endptr, int base )
{
bool neg = false;
unsigned long long result = Strtoull( str, endptr, base, &neg );
return rangeCheck( result, LLONG_MIN, LLONG_MAX, neg );
}
unsigned long
strtoul( const char* restrict str, char** restrict endptr, int base )
{
bool neg = false;
unsigned long long result = Strtoull( str, endptr, base, &neg );
return rangeCheck( result, 0, ULONG_MAX, false );
}
long
strtol( const char* restrict str, char** restrict endptr, int base )
{
bool neg = false;
unsigned long long result = Strtoull( str, endptr, base, &neg );
return rangeCheck( result, LONG_MIN, LONG_MAX, neg );
}
--
Ian Collins
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-21 12:09 +0100
Re: Code for strtol/strtoul Bartc <bc@freeuk.com> - 2015-03-21 11:33 +0000
Re: Code for strtol/strtoul Bartc <bc@freeuk.com> - 2015-03-21 11:47 +0000
Re: Code for strtol/strtoul Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-21 15:58 +0000
Re: Code for strtol/strtoul Lőrinczy Zsigmond <nospam@for.me> - 2015-03-21 16:10 +0100
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-21 16:34 +0100
Re: Code for strtol/strtoul Kaz Kylheku <kaz@kylheku.com> - 2015-03-21 16:10 +0000
Re: Code for strtol/strtoul James Kuyper <jameskuyper@verizon.net> - 2015-03-21 12:53 -0400
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-21 14:18 -0700
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-21 22:46 +0100
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-21 15:23 -0700
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-21 23:42 +0100
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-21 16:06 -0700
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-22 00:29 +0100
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-21 20:18 -0700
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-21 15:54 -0700
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-22 08:34 +0100
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-24 19:42 -0700
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-25 10:40 -0700
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-25 16:17 -0700
Re: Code for strtol/strtoul Keith Thompson <kst-u@mib.org> - 2015-03-25 20:27 -0700
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-28 09:08 -0700
Re: Code for strtol/strtoul Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-21 15:53 +0000
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-24 21:50 -0700
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-25 06:54 +0100
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-25 19:18 +1300
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-25 09:57 +0100
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-26 07:07 +1300
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-26 14:22 +1300
Re: Code for strtol/strtoul asetofsymbols@gmail.com - 2015-03-26 00:17 -0700
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-28 12:07 +1300
Re: Code for strtol/strtoul asetofsymbols@gmail.com - 2015-03-28 02:53 -0700
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-25 08:19 -0700
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-28 16:13 -0700
Re: Code for strtol/strtoul Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-25 13:42 +0000
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-25 17:20 -0700
Re: Code for strtol/strtoul Kaz Kylheku <kaz@kylheku.com> - 2015-03-26 04:16 +0000
Re: Code for strtol/strtoul asetofsymbols@gmail.com - 2015-03-26 00:27 -0700
Re: Code for strtol/strtoul Kaz Kylheku <kaz@kylheku.com> - 2015-03-26 13:44 +0000
Re: Code for strtol/strtoul fir <profesor.fir@gmail.com> - 2015-03-26 07:13 -0700
Re: Code for strtol/strtoul asetofsymbols@gmail.com - 2015-03-26 08:30 -0700
Re: Code for strtol/strtoul raltbos@xs4all.nl (Richard Bos) - 2015-03-29 15:13 +0000
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-28 09:47 -0700
Re: Code for strtol/strtoul Greg Martin <greg.at.softsprocket@dot.com> - 2015-03-26 15:00 +0000
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-27 07:12 +1300
Re: Code for strtol/strtoul Bartc <bc@freeuk.com> - 2015-03-26 19:11 +0000
Re: Code for strtol/strtoul Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-26 15:09 -0700
Re: Code for strtol/strtoul Richard Heathfield <rjh@cpax.org.uk> - 2015-03-26 22:13 +0000
Re: Code for strtol/strtoul Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-26 15:20 -0700
Re: Code for strtol/strtoul raltbos@xs4all.nl (Richard Bos) - 2015-03-30 09:59 +0000
Re: Code for strtol/strtoul Malcolm McLean <malcolm.mclean5@btinternet.com> - 2015-03-30 06:38 -0700
Re: Code for strtol/strtoul Richard Heathfield <rjh@cpax.org.uk> - 2015-03-30 14:41 +0100
Re: Code for strtol/strtoul raltbos@xs4all.nl (Richard Bos) - 2015-04-06 12:52 +0000
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-27 18:07 +1300
Re: Code for strtol/strtoul raltbos@xs4all.nl (Richard Bos) - 2015-03-29 15:17 +0000
Re: Code for strtol/strtoul Kaz Kylheku <kaz@kylheku.com> - 2015-03-29 15:26 +0000
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-30 07:09 +1300
Re: Code for strtol/strtoul raltbos@xs4all.nl (Richard Bos) - 2015-03-30 10:02 +0000
Re: Code for strtol/strtoul Bartc <bc@freeuk.com> - 2015-03-29 18:53 +0100
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-28 15:38 -0700
Re: Code for strtol/strtoul Robert Wessel <robertwessel2@yahoo.com> - 2015-03-21 16:48 -0500
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-22 20:45 +1300
Re: Code for strtol/strtoul Ike Naar <ike@iceland.freeshell.org> - 2015-03-23 09:40 +0000
Re: Code for strtol/strtoul Richard Heathfield <rjh@cpax.org.uk> - 2015-03-23 09:46 +0000
Re: Code for strtol/strtoul Reinhardt Behm <rbehm@hushmail.com> - 2015-03-23 18:44 +0800
Re: Code for strtol/strtoul Les Cargill <lcargill99@comcast.com> - 2015-03-23 20:29 -0500
Re: Code for strtol/strtoul Richard Heathfield <rjh@cpax.org.uk> - 2015-03-24 08:12 +0000
Re: Code for strtol/strtoul Robert Wessel <robertwessel2@yahoo.com> - 2015-03-23 05:27 -0500
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-24 07:03 +1300
Re: Code for strtol/strtoul Ike Naar <ike@iceland.freeshell.org> - 2015-03-23 22:40 +0000
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-24 17:17 +1300
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-24 21:42 -0700
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-25 17:55 +1300
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-25 08:43 -0700
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-26 14:15 +1300
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-28 14:53 -0700
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-29 11:04 +1300
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-30 12:34 -0700
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-31 21:20 +1300
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-24 22:31 -0700
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-25 19:30 +1300
Re: Code for strtol/strtoul Tim Rentsch <txr@alumni.caltech.edu> - 2015-03-25 08:24 -0700
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-25 22:43 +0100
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-27 19:18 +1300
Re: Code for strtol/strtoul Steve Thompson <stevet810@gmail.com> - 2015-03-27 15:02 +0000
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-27 16:10 +0100
Re: Code for strtol/strtoul Steve Thompson <stevet810@gmail.com> - 2015-03-27 22:44 +0000
Re: Code for strtol/strtoul raltbos@xs4all.nl (Richard Bos) - 2015-03-29 15:18 +0000
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-29 17:35 +0200
Re: Code for strtol/strtoul Robert Wessel <robertwessel2@yahoo.com> - 2015-03-28 03:57 -0500
Re: Code for strtol/strtoul jacob navia <jacob@jacob.remcomp.fr> - 2015-03-28 14:09 +0100
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-28 22:58 +1300
Re: Code for strtol/strtoul Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-28 11:33 +0000
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-29 08:49 +1300
Re: Code for strtol/strtoul Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-03-28 22:11 +0000
Re: Code for strtol/strtoul Ian Collins <ian-news@hotmail.com> - 2015-03-29 11:30 +1300
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