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Re: Idle: C library features wish-list.

From Kaz Kylheku <864-117-4973@kylheku.com>
Newsgroups comp.lang.c
Subject Re: Idle: C library features wish-list.
Date 2022-10-04 16:56 +0000
Organization A noiseless patient Spider
Message-ID <20221004011719.833@kylheku.com> (permalink)
References (1 earlier) <86y1txinka.fsf@linuxsc.com> <thdum3$23pod$2@dont-email.me> <20221003130059.385@kylheku.com> <OcI_K.166108$w35c.86764@fx47.iad> <thfthv$2bf07$1@dont-email.me>

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On 2022-10-04, BGB <cr88192@gmail.com> wrote:
> In some cases, one "actually needs" a copy operation that will turn the 
> output into a repeating pattern of bytes whenever one forward-copies a 
> chunk of memory over the top of itself.

You mention this in the context of LZ77 deflate, but I don't see
any such thing in zlib sources. There is a zmemcpy which
in some cases is just a macro for memcpy.

Is Adler missing some clue or something?

> Also it can be used as a way to implement a "multi byte memset", say for 
> example, if one wants a fast way to flood-fill a chunk of memory with 
> 0xDEADBEEF or similar, ...

A multi-byte memset that is reading from the area where it is writing
seems inefficient, particularly if the memory is cache-cold,
since it will actually be sucking the memory into the processor's
caches only to turn around a blast it out again.

You really want an actual multi-byte memset for that use case.

-- 
TXR Programming Language: http://nongnu.org/txr
Cygnal: Cygwin Native Application Library: http://kylheku.com/cygnal

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Thread

Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-09-30 16:34 -0500
  Re: Idle: C library features wish-list. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-10-02 20:38 -0700
    Re: Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-10-03 01:14 -0500
      Re: Idle: C library features wish-list. Kaz Kylheku <864-117-4973@kylheku.com> - 2022-10-03 20:40 +0000
        Re: Idle: C library features wish-list. scott@slp53.sl.home (Scott Lurndal) - 2022-10-03 21:10 +0000
          Re: Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-10-03 19:07 -0500
            Re: Idle: C library features wish-list. scott@slp53.sl.home (Scott Lurndal) - 2022-10-04 13:43 +0000
              Re: Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-10-04 15:20 -0500
                Re: Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-10-05 03:58 -0500
            Re: Idle: C library features wish-list. Kaz Kylheku <864-117-4973@kylheku.com> - 2022-10-04 16:56 +0000
              Re: Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-10-04 18:30 -0500
        Re: Idle: C library features wish-list. BGB <cr88192@gmail.com> - 2022-10-03 18:19 -0500
      Re: Idle: C library features wish-list. Tim Rentsch <tr.17687@z991.linuxsc.com> - 2022-11-19 06:54 -0800
    Re: Idle: C library features wish-list. gazelle@shell.xmission.com (Kenny McCormack) - 2022-10-03 09:29 +0000

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