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Re: On endianness, many #ifdefs, and the need thereof

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Daniel <danielaparker@gmail.com> writes:
>On Thursday, October 3, 2019 at 7:46:13 AM UTC-4, David Brown wrote:
>> 
>> A little look suggests that it is for parsing binary JSON formats (like
>> UBJSON), rather than standard text-based JSON.  But is still not
>> necessary, and I doubt if the code's algorithm is more efficient than
>> the obvious endian independent method.
>
>An "obvious endian independent method"? For decoding and encoding CBOR, 
>Message Pack, UBJSON, and BSON into native types? What are you referring to?
>
>CBOR encodes 8, 16, 32, and 64 bit signed and unsigned ints as big endian, and 
>16, 32, and 64 bit floats as big endian. "CBOR for typed arrays" accommodates 
>typed arrays of 8, 16, 32, and 64 bit signed and unsigned ints, and 16, 32, 
>64, 128 bit floating point numbers, in either little endian or big endian. 
>Could you explain the "obvious endian independent method" that will encode and 
>decode that?

If the incoming big-endian data is treated as a sequence of bytes, you
can easily reconstruct a binary value simply shifting the data into the
correct sized container a byte at a time.

  uint64_t  value = 0ul;
  char *bp = &buffer[first_byte_of_uint64_big_endian_data];

  for (size_t i = 0; i < sizeof(uint64_t); i++) {
      value <<= 8;
      value |= *bp++;
  }

This works regardless of the host endianness.

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On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-02 04:00 -0700
  Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-02 13:26 +0200
    Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-02 08:59 -0700
  Re: On endianness, many #ifdefs, and the need thereof Öö Tiib <ootiib@hot.ee> - 2019-10-02 05:42 -0700
  Re: On endianness, many #ifdefs, and the need thereof Juha Nieminen <nospam@thanks.invalid> - 2019-10-02 12:53 +0000
    Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-02 15:05 +0200
      Re: On endianness, many #ifdefs, and the need thereof scott@slp53.sl.home (Scott Lurndal) - 2019-10-02 13:54 +0000
        Re: On endianness, many #ifdefs, and the need thereof Keith Thompson <kst-u@mib.org> - 2019-10-02 12:54 -0700
          Re: On endianness, many #ifdefs, and the need thereof scott@slp53.sl.home (Scott Lurndal) - 2019-10-02 20:16 +0000
        Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-03 09:48 +0200
    Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-02 07:52 -0700
      Re: On endianness, many #ifdefs, and the need thereof Öö Tiib <ootiib@hot.ee> - 2019-10-02 08:04 -0700
        Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-02 08:31 -0700
          Re: On endianness, many #ifdefs, and the need thereof Juha Nieminen <nospam@thanks.invalid> - 2019-10-02 21:32 +0000
      Re: On endianness, many #ifdefs, and the need thereof Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-03 11:33 +0000
        Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-03 13:46 +0200
          Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-03 05:56 -0700
            Re: On endianness, many #ifdefs, and the need thereof scott@slp53.sl.home (Scott Lurndal) - 2019-10-03 13:17 +0000
              Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-03 16:03 +0200
                Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-03 07:13 -0700
          Re: On endianness, many #ifdefs, and the need thereof Jorgen Grahn <grahn+nntp@snipabacken.se> - 2019-10-03 18:51 +0000
          Re: On endianness, many #ifdefs, and the need thereof Keith Thompson <kst-u@mib.org> - 2019-10-03 14:28 -0700
            Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-04 10:11 +0200
              Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-04 09:00 -0700
        Re: On endianness, many #ifdefs, and the need thereof Paavo Helde <myfirstname@osa.pri.ee> - 2019-10-03 14:46 +0300
        Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-03 05:40 -0700
  Re: On endianness, many #ifdefs, and the need thereof Bonita Montero <Bonita.Montero@gmail.com> - 2019-10-02 15:10 +0200
  Re: On endianness, many #ifdefs, and the need thereof Barry Schwarz <schwarzb@dqel.com> - 2019-10-02 08:33 -0700
    Re: On endianness, many #ifdefs, and the need thereof David Brown <david.brown@hesbynett.no> - 2019-10-03 09:54 +0200
  Re: On endianness, many #ifdefs, and the need thereof "Alf P. Steinbach" <alf.p.steinbach+usenet@gmail.com> - 2019-10-02 19:35 +0200
    Re: On endianness, many #ifdefs, and the need thereof Daniel <danielaparker@gmail.com> - 2019-10-02 15:39 -0700
  Re: On endianness, many #ifdefs, and the need thereof "Oliver S." <Follow.Me@gmx.net> - 2019-10-02 19:59 +0200

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