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Re: Check if all 256 bits are clear or set ?

From Ben Bacarisse <ben.usenet@bsb.me.uk>
Newsgroups comp.lang.c
Subject Re: Check if all 256 bits are clear or set ?
Date 2021-11-04 17:13 +0000
Organization A noiseless patient Spider
Message-ID <874k8reted.fsf@bsb.me.uk> (permalink)
References (3 earlier) <sluqck$fm1$3@dont-email.me> <slur71$oau$1@dont-email.me> <slvt7q$r5h$1@dont-email.me> <87zgqkdudb.fsf@bsb.me.uk> <sm13fm$1fc$1@dont-email.me>

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Bonita Montero <Bonita.Montero@gmail.com> writes:

> You're right, but this works:
>
> bool test256( char *p, bool set )
> {
> 	uint64_t *p64 = (uint64_t *)p;

This is undefined id p is not properly aligned for uint64_t.

> 	return !(p64[0] + set) & !(p64[1] + set) & !(p64[2] + set) & !(p64[3] + set);
> }
>

-- 
Ben.

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Thread

Check if all 256 bits are clear or set ? skybuck2000 <skybuck2000@hotmail.com> - 2021-10-28 17:47 -0700
  Re: Check if all 256 bits are clear or set ? skybuck2000 <skybuck2000@hotmail.com> - 2021-10-28 18:02 -0700
    Re: Check if all 256 bits are clear or set ? skybuck2000 <skybuck2000@hotmail.com> - 2021-10-28 18:12 -0700
      Re: Check if all 256 bits are clear or set ? skybuck2000 <skybuck2000@hotmail.com> - 2021-10-28 19:18 -0700
        Re: Check if all 256 bits are clear or set ? skybuck2000 <skybuck2000@hotmail.com> - 2021-10-29 05:16 -0700
  Re: Check if all 256 bits are clear or set ? Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2021-11-03 11:11 +1100
    Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-03 11:50 +0000
      Re: Check if all 256 bits are clear or set ? Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2021-11-06 16:08 +1100
        Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-06 11:02 +0000
          Re: Check if all 256 bits are clear or set ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-11-06 15:04 -0700
            Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-06 22:06 +0000
            Re: Check if all 256 bits are clear or set ? Peter 'Shaggy' Haywood <phaywood@alphalink.com.au> - 2021-11-13 11:54 +1100
          Re: Check if all 256 bits are clear or set ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-11-06 15:22 -0700
            Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-07 00:08 +0000
              Re: Check if all 256 bits are clear or set ? Tim Rentsch <tr.17687@z991.linuxsc.com> - 2021-11-07 08:12 -0800
        Re: Check if all 256 bits are clear or set ? skybuck2000 <skybuck2000@hotmail.com> - 2021-11-23 08:23 -0800
      Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-06 15:01 +0100
  Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-03 21:04 +0100
    Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-03 21:09 +0100
      Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-03 21:11 +0100
        Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-03 21:25 +0100
          Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-04 07:05 +0100
            Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-04 11:37 +0000
              Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-04 17:58 +0100
                Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-04 17:13 +0000
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-04 18:15 +0100
                Re: Check if all 256 bits are clear or set ? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2021-11-04 17:27 +0000
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-04 18:29 +0100
                Re: Check if all 256 bits are clear or set ? scott@slp53.sl.home (Scott Lurndal) - 2021-11-04 17:28 +0000
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-05 11:56 +0100
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-05 18:20 +0100
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-05 18:32 +0100
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-04 18:13 +0100
                Re: Check if all 256 bits are clear or set ? Manfred <noname@add.invalid> - 2021-11-04 19:28 +0100
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-04 20:29 +0100
                Re: Check if all 256 bits are clear or set ? Manfred <noname@add.invalid> - 2021-11-05 02:06 +0100
                Re: Check if all 256 bits are clear or set ? Bonita Montero <Bonita.Montero@gmail.com> - 2021-11-05 08:57 +0100
              Re: Check if all 256 bits are clear or set ? Bart <bc@freeuk.com> - 2021-11-04 18:01 +0000

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