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Groups > comp.lang.c > #150919
| From | Keith Thompson <Keith.S.Thompson+u@gmail.com> |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Protable way of reading str[4] as uint32_t |
| Date | 2020-03-30 19:04 -0700 |
| Organization | None to speak of |
| Message-ID | <875zeluvnz.fsf@nosuchdomain.example.com> (permalink) |
| References | <40d1f926-8737-4332-93f2-c37c46f731f9@googlegroups.com> <yOvgG.106450$Gy2.9178@fx30.iad> |
Richard Damon <Richard@Damon-Family.org> writes:
> On 3/30/20 2:42 PM, wyniijj@gmail.com wrote:
>> I'd like to read the value a.value in the following program as 0x78563412 in a
>> portable way, none of hton or ntoh is useful. How should I do?
>>
>> #include <stdio.h>
>> #include <arpa/inet.h>
>>
>> int main()
>> {
>> union {
>> char str[4];
>> uint32_t value;
>> } a;
>>
>> a.str[0]=0x12;
>> a.str[1]=0x34;
>> a.str[2]=0x56;
>> a.str[3]=0x78;
[...]
> Network order is Big Endian, your problem statement defines decoding
> little endian, so the network order functions won't work.
>
> In my mind the simplest is:
>
> a.ser[0] | (a.str[1] << 8) | (a.str[2] << 16) | (a.str[3] << 24)
>
> i.e., be explicit and access by bytes in the order you want.
And definitely use unsigned char rather than char, and test with values
exceeding 0x7f.
[...]
--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
Working, but not speaking, for Philips Healthcare
void Void(void) { Void(); } /* The recursive call of the void */
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Protable way of reading str[4] as uint32_t wyniijj@gmail.com - 2020-03-30 11:42 -0700
Re: Protable way of reading str[4] as uint32_t Ben Bacarisse <ben.usenet@bsb.me.uk> - 2020-03-30 20:14 +0100
Re: Protable way of reading str[4] as uint32_t Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-03-30 20:11 +0000
Re: Protable way of reading str[4] as uint32_t Richard Damon <Richard@Damon-Family.org> - 2020-03-30 20:04 -0400
Re: Protable way of reading str[4] as uint32_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-03-30 19:04 -0700
Re: Protable way of reading str[4] as uint32_t wyniijj@gmail.com - 2020-03-30 23:30 -0700
Re: Protable way of reading str[4] as uint32_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-03-31 10:59 -0700
Re: Protable way of reading str[4] as uint32_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-03-31 12:19 -0700
Re: Protable way of reading str[4] as uint32_t wyniijj@gmail.com - 2020-04-01 06:37 -0700
Re: Protable way of reading str[4] as uint32_t wyniijj@gmail.com - 2020-03-30 23:28 -0700
Re: Portable way of reading str[4] as uint32_t Spiros Bousbouras <spibou@gmail.com> - 2020-03-31 11:29 +0000
Re: Portable way of reading str[4] as uint32_t wyniijj@gmail.com - 2020-03-31 09:59 -0700
Re: Portable way of reading str[4] as uint32_t Spiros Bousbouras <spibou@gmail.com> - 2020-03-31 18:03 +0000
Re: Portable way of reading str[4] as uint32_t Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-02 19:09 -0700
Re: Portable way of reading str[4] as uint32_t Spiros Bousbouras <spibou@gmail.com> - 2020-04-03 05:02 +0000
Re: Portable way of reading str[4] as uint32_t James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 01:10 -0400
Re: Portable way of reading str[4] as uint32_t gazelle@shell.xmission.com (Kenny McCormack) - 2020-04-03 08:18 +0000
Re: Portable way of reading str[4] as uint32_t Spiros Bousbouras <spibou@gmail.com> - 2020-04-03 09:48 +0000
Re: Portable way of reading str[4] as uint32_t gazelle@shell.xmission.com (Kenny McCormack) - 2020-04-03 11:07 +0000
Re: Portable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-04-03 09:41 -0500
Re: Portable way of reading str[4] as uint32_t Malcolm McLean <malcolm.arthur.mclean@gmail.com> - 2020-04-03 07:51 -0700
Re: Portable way of reading str[4] as uint32_t Richard Damon <Richard@Damon-Family.org> - 2020-04-03 12:09 -0400
Re: Portable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-04-03 13:19 -0500
Re: Portable way of reading str[4] as uint32_t James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 14:52 -0400
Re: Portable way of reading str[4] as uint32_t Keith Thompson <Keith.S.Thompson+u@gmail.com> - 2020-04-03 12:10 -0700
Re: Portable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-04-03 15:17 -0500
Re: Portable way of reading str[4] as uint32_t James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-03 23:39 -0400
Re: Portable way of reading str[4] as uint32_t Spiros Bousbouras <spibou@gmail.com> - 2020-04-03 21:28 +0000
Re: Portable way of reading str[4] as uint32_t Tim Rentsch <tr.17687@z991.linuxsc.com> - 2020-04-04 19:28 -0700
Re: Protable way of reading str[4] as uint32_t Richard Damon <Richard@Damon-Family.org> - 2020-03-31 08:05 -0400
Re: Protable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-03-31 09:12 -0500
Re: Protable way of reading str[4] as uint32_t Philipp Klaus Krause <pkk@spth.de> - 2020-03-31 17:27 +0200
Re: Protable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-03-31 18:26 -0500
Re: Protable way of reading str[4] as uint32_t Jorgen Grahn <grahn+nntp@snipabacken.se> - 2020-04-01 06:03 +0000
Re: Protable way of reading str[4] as uint32_t Richard Damon <Richard@Damon-Family.org> - 2020-04-01 08:17 -0400
Re: Protable way of reading str[4] as uint32_t James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-01 09:57 -0400
Re: Protable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-04-01 09:47 -0500
Re: Protable way of reading str[4] as uint32_t James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-04-01 11:48 -0400
Re: Protable way of reading str[4] as uint32_t BGB <cr88192@gmail.com> - 2020-04-01 12:37 -0500
Re: Protable way of reading str[4] as uint32_t James Kuyper <jameskuyper@alumni.caltech.edu> - 2020-03-31 12:56 -0400
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