Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
| From | Ben Bacarisse <ben.usenet@bsb.me.uk> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: How to encode/decode string of decimal digits |
| Date | 2015-10-22 15:51 +0100 |
| Organization | A noiseless patient Spider |
| Message-ID | <87vb9zez2u.fsf@bsb.me.uk> (permalink) |
| References | (5 earlier) <n07uqm$g1h$1@dont-email.me> <n08c8u$6ef$1@dont-email.me> <n0ab85$e5r$1@dont-email.me> <n0ai26$56d$1@dont-email.me> <87fv13gjgr.fsf@bsb.me.uk> |
Ben Bacarisse <ben.usenet@bsb.me.uk> writes:
> pozz <pozzugno@gmail.com> writes:
>
>> Il 22/10/2015 11:47, David Brown ha scritto:
<snip>
>>> The simple solution here would be to map decimal digits 0 to 9 to hex
>>> digits 0 to 9, and "space" or "no digit" to hex 'a'. This would turn
>>> those strings into:
>>>
>>> 0xaaaaaaaaaaaa1234
>>> 0xaaaaaaaaaaa01234
>>> 0xaaaaaaaa00001234
>>> 0xa123456789012345
>>> 0xaaaaaaaaa9874321
>>>
>>> Clear, simple, fast to implement and easy for debugging (since the hex
>>> values are human-readable).
>>
>> Ok for "easy for debugging" (you can read directly the string), but is
>> the encoding process "simpler" than strtoull()/strlen()?
<snip>
> uint64_t encode(const char *str)
> {
> uint64_t r = 0xaaaaaaaaaaaaaaaa;
> while (*str) r = (r << 4) + *str++ - '0';
> return r;
> }
Just to keep things clear, Tim's strtoull(...) << 5 | strlen() version
can represent all the valid strings up to 17 digits because it does not
use a full byte for the length as your variation did. The plain
BCD+blank encoding will do only 16, but that seemed to be enough for
you. Fancier encodings can get up to 18 digits and, if I've counted
them right, it is theoretically possible to encode all strings up to 19
digits in 64 bits, but that's likely to be very messy.
<snip>
--
Ben.
Back to comp.lang.c | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-19 14:28 +0200
Re: How to encode/decode string of decimal digits Bartc <bc@freeuk.com> - 2015-10-19 14:07 +0100
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-19 15:58 +0200
Re: How to encode/decode string of decimal digits Bartc <bc@freeuk.com> - 2015-10-19 15:22 +0100
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 15:58 +0100
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 22:28 +0100
Re: How to encode/decode string of decimal digits Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-19 13:30 -0400
Re: How to encode/decode string of decimal digits Robert Wessel <robertwessel2@yahoo.com> - 2015-10-19 16:18 -0500
Re: How to encode/decode string of decimal digits Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-19 21:38 -0400
Re: How to encode/decode string of decimal digits Jorgen Grahn <grahn+nntp@snipabacken.se> - 2015-10-20 08:00 +0000
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-19 15:50 +0100
Re: How to encode/decode string of decimal digits Keith Thompson <kst-u@mib.org> - 2015-10-19 09:01 -0700
Re: How to encode/decode string of decimal digits Tim Rentsch <txr@alumni.caltech.edu> - 2015-10-19 12:11 -0700
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-20 13:51 +0200
Re: How to encode/decode string of decimal digits Bartc <bc@freeuk.com> - 2015-10-20 13:38 +0100
Re: How to encode/decode string of decimal digits glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-20 16:05 +0000
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-21 09:29 +0200
Re: How to encode/decode string of decimal digits Bartc <bc@freeuk.com> - 2015-10-21 11:27 +0100
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-21 17:55 +0200
Re: How to encode/decode string of decimal digits Eric Sosman <esosman@comcast-dot-net.invalid> - 2015-10-21 08:03 -0400
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-21 17:53 +0200
Re: How to encode/decode string of decimal digits supercat@casperkitty.com - 2015-10-21 09:37 -0700
Re: How to encode/decode string of decimal digits David Brown <david.brown@hesbynett.no> - 2015-10-22 11:47 +0200
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-22 13:44 +0200
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-22 13:45 +0100
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-22 15:51 +0100
Re: How to encode/decode string of decimal digits supercat@casperkitty.com - 2015-10-22 09:31 -0700
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-22 20:48 +0100
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-23 10:14 +0200
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-23 11:14 +0100
Re: How to encode/decode string of decimal digits Bartc <bc@freeuk.com> - 2015-10-23 11:47 +0100
Re: How to encode/decode string of decimal digits Ben Bacarisse <ben.usenet@bsb.me.uk> - 2015-10-23 13:22 +0100
Re: How to encode/decode string of decimal digits David Brown <david.brown@hesbynett.no> - 2015-10-22 15:07 +0200
Re: How to encode/decode string of decimal digits glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-22 22:05 +0000
Re: How to encode/decode string of decimal digits pozz <pozzugno@gmail.com> - 2015-10-23 10:15 +0200
Re: How to encode/decode string of decimal digits glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2015-10-19 22:02 +0000
Re: How to encode/decode string of decimal digits supercat@casperkitty.com - 2015-10-20 10:09 -0700
csiph-web