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Re: Feature-Request: sendfile(2)

From: Daniel Stenberg via curl-library <curl-library_at_cool.haxx.se>
Date: Thu, 25 Feb 2021 22:56:07 +0100 (CET)

On Thu, 25 Feb 2021, Emil Engler via curl-library wrote:

> I recently thought about implementing the syscall sendfile(2) into
> libcurl to speed up downloads to a file.

An interesting idea, but one full of caveats.

sendfile would only work (effectively) for clear-text downloads using TCP (ie
not TLS nor UDP and HTTP/2 isn't really done for it either and not compressed
or chunked HTTP/1 either) but I still think the "downloads to a file
(descriptor)" is the biggest limiting factor.

The only time libcurl knows that it downloads to a file is when the write
callback is left at default and only CURLOPT_WRITEDATA is set, which not even
the curl tool does...

I'm not dismissing the idea, but it certainly isn't entirely straight-forward.

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Received on 2021-02-25