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Re: Making custom binary input ports unbuffered
From: |
Ludovic Courtès |
Subject: |
Re: Making custom binary input ports unbuffered |
Date: |
Wed, 15 Jan 2014 12:48:11 +0100 |
User-agent: |
Gnus/5.130007 (Ma Gnus v0.7) Emacs/24.3 (gnu/linux) |
Mark H Weaver <address@hidden> skribis:
> address@hidden (Ludovic Courtès) writes:
>
>> As discussed on IRC, our R6 custom binary input ports (CBIPs) are
>> currently buffered. The buffer is hard-coded and setvbuf doesn’t work
>> on non-file ports.
>
> [...]
>
>> The patch below makes CBIPs unbuffered (see the tests for the properties
>> it gives.) It works thanks to the optimization in ‘scm_c_read’ for
>> unbuffered binary ports.
>
> When you say "It works thanks to the optimization in 'scm_c_read'", do
> you mean that something will be broken if another method of reading is
> used?
No; I mean that without that optimization ‘read!’ would be called for
one byte at a time.
>> This is going to be a performance hit for applications that read things
>> byte by byte, *or* via textual procedures (‘scm_getc’, ‘get-string’,
>> etc.) But the assumption is that people rather use ‘get-bytevector-n’
>> (or similar) to get a chunk of data.
>>
>> However! There are places in (web ...) where CBIPs are used for mixed
>> binary/textual input. When that happens, all the accesses end up being
>> unbuffered, which really sucks.
>>
>> So, what do we do? :-)
>
> While I agree that CBIPs should be unbuffered by default, I think it's
> important to have a way to enable buffering, even if it's not portable.
Yeah, that’s probably the right thing to do.
I’m a bit afraid of the consequences of allowing non-file ports for
‘setvbuf’, but I’ll experiment and see if it causes any problems.
Thanks for your feedback!
Ludo’.
- Making custom binary input ports unbuffered, Ludovic Courtès, 2014/01/14
- Re: Making custom binary input ports unbuffered, Mark H Weaver, 2014/01/15
- Re: Making custom binary input ports unbuffered,
Ludovic Courtès <=
- Re: Making custom binary input ports unbuffered, Ludovic Courtès, 2014/01/15
- Re: Making custom binary input ports unbuffered, Mark H Weaver, 2014/01/15
- Re: Making custom binary input ports unbuffered, Ludovic Courtès, 2014/01/16
- Re: Making custom binary input ports unbuffered, Ludovic Courtès, 2014/01/18
- Re: Making custom binary input ports unbuffered, Mark H Weaver, 2014/01/21
- Re: Making custom binary input ports unbuffered, Ludovic Courtès, 2014/01/21
- Re: Making custom binary input ports unbuffered, Mark H Weaver, 2014/01/21
- Re: Making custom binary input ports unbuffered, Ludovic Courtès, 2014/01/21