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Use memrchr or similar in LineWriter::write #30076

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bluss opened this issue Nov 26, 2015 · 1 comment
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Use memrchr or similar in LineWriter::write #30076

bluss opened this issue Nov 26, 2015 · 1 comment

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@bluss
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bluss commented Nov 26, 2015

The LineWriter (used by stdout) searches for a newline in each .write() call. As compiled today, this byte search compiles to a byte-by-byte loop. This is a very hot loop, and unnecessarily so if you output data that's not line delimited. Using memchr or equivalent would improve this.
fhahn added a commit to fhahn/rust that referenced this issue Dec 1, 2015
@fhahn
Use libc::memchr instead of iter().rposition(), closes rust-lang#30076
bb3bf3f
fhahn added a commit to fhahn/rust that referenced this issue Dec 1, 2015
@fhahn
Use libc::memchr instead of iter().rposition(), closes rust-lang#30076
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@fhahn fhahn mentioned this issue Dec 1, 2015
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@bluss bluss changed the title Use memchr or similar in LineWriter::write Use memrchr or similar in LineWriter::write Dec 2, 2015
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bluss commented Dec 2, 2015

Of course memrchr, I did in fact miss the position vs rposition difference on first reading.

@fhahn fhahn mentioned this issue Dec 14, 2015
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bors added a commit that referenced this issue Dec 19, 2015
@bors
Auto merge of #30381 - fhahn:memchr-in-std, r=alexcrichton
8ad12c3 
This PR adds `memchr`and `memrchr` based on @BurntSushi 's rust-memchr crate to libstd (as discussed in #30151).

I've update some places in libstd to use memchr/memrchr, but I am not sure if there are other places where it could be used as well.

ref #30076
@bors bors closed this as completed in de3e843 Dec 19, 2015
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@bluss