stream: remove unreachable code by lpinca · Pull Request #18239 · nodejs/node

lpinca · 2018-01-18T19:08:29Z

First commit remove some unreachable code. BufferList.prototype.concat() is not called when there is only a buffer in the list.

Second commit fixes a test.

Checklist

make -j4 test (UNIX), or vcbuild test (Windows) passes
tests and/or benchmarks are included
documentation is changed or added
commit message follows commit guidelines

Affected core subsystem(s)

stream, test

To avoid a function call `BufferList.prototype.concat()` is not called when there is only a buffer in the list. That buffer is instead accessed directly.

The `n` argument of `BufferList.prototype.concat()` is not the number of `Buffer` instances in the list, but their total length when concatenated.

MoonBall · 2018-01-20T02:06:17Z

It's better to modify function fromList(n, state) in lib/_stream_readable.js by deleting the code, because BufferList is a independent module.

lpinca · 2018-01-20T06:44:32Z

@MoonBallBufferList is an internal module so it doesn't really matter and I guess it was done like this to avoid the function call.

The _stream_readable module is plenty of code that use internal details of BufferList.

MoonBall · 2018-01-20T07:23:19Z

ok. I agree.

targos · 2018-01-20T09:08:18Z

/cc @nodejs/streams

mcollina · 2018-01-20T20:59:53Z

I'm not super comfortable with this change.
What would happen if it happens? Any error would be good.

lpinca · 2018-01-20T21:14:58Z

What would happen if it happens?

Do you mean if BufferList#concat() is called when there is only one element in the list and this patch is applied? If so, nothing, it will still work as expected just without the fast path (which is already here).

mcollina · 2018-01-20T21:19:56Z

Can you restore the test then?

lpinca · 2018-01-20T21:31:49Z

+
+const copy = list.concat(3);

-assert.strictEqual(list.concat(1), 'foo');


@mcollina this is wrong whether or not the change in BufferList.js is applied.
The test uses a string, probably for simplicity, but concat() only works with buffers.
The n argument (1) was wrong and irrelevant. You could have used any argument and the test would have still passed.

lpinca · 2018-01-20T22:22:32Z

FWIW the fixed test actually tests the impossible case where BufferList#concat() is called and there is only one buffer in the list. Unlike the fast path, it creates a copy.

mcollina

LGTM, perfect

lpinca · 2018-01-21T09:38:45Z

CI: https://ci.nodejs.org/job/node-test-pull-request/12650/

To avoid a function call `BufferList.prototype.concat()` is not called when there is only a buffer in the list. That buffer is instead accessed directly. PR-URL: #18239 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

The `n` argument of `BufferList.prototype.concat()` is not the number of `Buffer` instances in the list, but their total length when concatenated. PR-URL: #18239 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lpinca · 2018-01-24T15:31:45Z

Landed in e65a6e8...2313424.

To avoid a function call `BufferList.prototype.concat()` is not called when there is only a buffer in the list. That buffer is instead accessed directly. PR-URL: #18239 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

The `n` argument of `BufferList.prototype.concat()` is not the number of `Buffer` instances in the list, but their total length when concatenated. PR-URL: #18239 Reviewed-By: Matteo Collina <matteo.collina@gmail.com>

lpinca added 2 commits January 18, 2018 18:39

stream: remove unreachable code
5593b51
To avoid a function call `BufferList.prototype.concat()` is not called when there is only a buffer in the list. That buffer is instead accessed directly.

test: use correct size in test-stream-buffer-list
4461fa5
The `n` argument of `BufferList.prototype.concat()` is not the number of `Buffer` instances in the list, but their total length when concatenated.

lpinca added stream Issues and PRs related to the stream subsystem. test Issues and PRs related to the tests. labels Jan 18, 2018

lpinca commented Jan 20, 2018
View reviewed changes

mcollina approved these changes Jan 20, 2018
View reviewed changes

lpinca closed this Jan 24, 2018

lpinca deleted the remove/unreachable-code branch January 24, 2018 15:32

evanlucas mentioned this pull request Jan 30, 2018
v9.5.0 release proposal #18464
Merged

This was referenced Apr 7, 2024
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[Snyk] Security upgrade eslint from 4.19.1 to 9.0.0 aliscco/alisco-node#1366
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baby636 mentioned this pull request Apr 7, 2024
[Snyk] Security upgrade eslint from 7.32.0 to 9.0.0 baby636/node#145
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ryan-ally mentioned this pull request Apr 7, 2024
[Snyk] Security upgrade eslint from 6.8.0 to 9.0.0 ryan-ally/node#106
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aliscco mentioned this pull request Apr 7, 2024
[Snyk] Security upgrade eslint from 3.19.0 to 9.0.0 aliscco/alisco-node#1372
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leonardoadame mentioned this pull request Apr 7, 2024
[Snyk] Security upgrade eslint from 3.19.0 to 9.0.0 leonardoadame/node#770
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This was referenced Apr 8, 2024
[Snyk] Security upgrade eslint from 4.19.1 to 9.0.0 aliscco/alisco-node#1375
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stream: remove unreachable code - #18239

stream: remove unreachable code #18239
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		const copy = list.concat(3);

		assert.strictEqual(list.concat(1), 'foo');

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lpinca commented Jan 18, 2018

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