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Re: Protable way of reading str[4] as uint32_t

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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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