str: common logic for replace & replacen #56464

ljedrz · 2018-12-03T15:49:53Z

The logic of str::replace and str::replacen is almost identical - we can use a common helper function. The initial capacity of the resulting string was different (0 vs. 32), but I propose a different approach: use the same capacity as in the original string; this will neither reallocate too often (or not at all if the substitute's length is the same as the substituted bit's), nor will it overallocate for short strings. It will also be an exact fit in case of no pattern hits.

rust-highfive · 2018-12-03T15:49:56Z

r? @kennytm

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kennytm · 2018-12-03T15:52:01Z

I'm going to rewrite these functions for #56345, would you mind if I just incorporate these changes directly into the new PR?

ljedrz · 2018-12-03T15:55:09Z

Sure, I don't mind at all 👌.

kennytm · 2018-12-03T15:57:50Z

OK I'll close this when that PR is submitted.

rust-highfive · 2018-12-03T16:55:35Z

The job x86_64-gnu-llvm-5.0 of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:070486b0:start=1543852283535146173,finish=1543852370569137316,duration=87033991143
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#Pull-Requests-and-Security-Restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
Setting environment variables from .travis.yml
$ export IMAGE=x86_64-gnu-llvm-5.0
---
travis_time:start:test_codegen
Check compiletest suite=codegen mode=codegen (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
[00:52:55] 
[00:52:55] running 120 tests
[00:52:58] i..ii...iii..iiii.....i...i..........i..iii.............i.....i.....ii...i..i.ii...............i..ii 100/120
[00:52:59] ..ii.i.....iiii.....
[00:52:59] 
[00:52:59]  finished in 3.260
[00:52:59] travis_fold:end:test_codegen

---
travis_time:start:test_debuginfo
Check compiletest suite=debuginfo mode=debuginfo-both (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
[00:53:12] 
[00:53:12] running 118 tests
[00:53:35] .iiiii...i.....i..i...i..i.i..i.i..i.....i..i....i..........iiii.........i.i....i...i.......ii.i.i.i 100/118
[00:53:38] ......iii.i.....ii
[00:53:38] 
[00:53:38]  finished in 26.194
[00:53:38] travis_fold:end:test_debuginfo

---
[01:01:15]    Compiling rand_core v0.2.1
[01:01:15]    Compiling libc v0.2.43
[01:01:16]    Compiling rand v0.5.5
[01:01:20]    Compiling alloc v0.0.0 (/checkout/src/liballoc)
[01:01:25] error: function is never used: `replace_helper`
[01:01:25]     |
[01:01:25]     |
[01:01:25] 609 | fn replace_helper<'a, P: Pattern<'a>>(s: &'a str, pat: P, to: &str, lim: Option<usize>) -> String {
[01:01:25]     |
[01:01:25]     = note: `-D dead-code` implied by `-D warnings`
[01:01:25] 
[01:01:25] error: aborting due to previous error
[01:01:25] error: aborting due to previous error
[01:01:25] 
[01:01:25] error: Could not compile `alloc`.
[01:01:25] warning: build failed, waiting for other jobs to finish...
[01:02:29] error: build failed
[01:02:29] 
[01:02:29] 
[01:02:29] command did not execute successfully: "/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo" "test" "--target" "x86_64-unknown-linux-gnu" "-j" "4" "--release" "--locked" "--color" "always" "--features" "panic-unwind backtrace" "--manifest-path" "/checkout/src/libstd/Cargo.toml" "-p" "alloc" "--" "--quiet"
[01:02:29] 
[01:02:29] 
[01:02:29] failed to run: /checkout/obj/build/bootstrap/debug/bootstrap test
[01:02:29] Build completed unsuccessfully in 0:19:40
[01:02:29] Build completed unsuccessfully in 0:19:40
[01:02:29] make: *** [check] Error 1
[01:02:29] Makefile:58: recipe for target 'check' failed
The command "stamp sh -x -c "$RUN_SCRIPT"" exited with 2.
travis_time:start:00239916
$ date && (curl -fs --head https://google.com | grep ^Date: | sed 's/Date: //g' || true)
Mon Dec  3 16:55:30 UTC 2018

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

Centril · 2018-12-03T19:36:46Z

src/liballoc/str.rs

@@ -622,3 +605,16 @@ impl str {
 pub unsafe fn from_boxed_utf8_unchecked(v: Box<[u8]>) -> Box<str> {
 Box::from_raw(Box::into_raw(v) as *mut str)
 }
+
+fn replace_helper<'a, P: Pattern<'a>>(s: &'a str, pat: P, to: &str, lim: Option<usize>) -> String {


A comment would be nice... :)

Centril · 2018-12-03T19:36:48Z

src/liballoc/str.rs

+ let mut last_end = 0;
+ let limit = if let Some(limit) = lim { limit } else { s.len() };
+ for (start, part) in s.match_indices(pat).take(limit) {
+ result.push_str(unsafe { s.get_unchecked(last_end..start) });


And a comment explaining why this is safe as well...

Centril · 2018-12-03T19:36:50Z

src/liballoc/str.rs

+ result.push_str(to);
+ last_end = start + part.len();
+ }
+ result.push_str(unsafe { s.get_unchecked(last_end..s.len()) });


and here...

Dylan-DPC-zz · 2018-12-10T10:37:13Z

@ljedrz can you update this PR with the changes requested above?

ljedrz · 2018-12-10T10:42:15Z

@Dylan-DPC actually @kennytm is interested in intercepting this change (see #56464 (comment)); that's why I'm not updating this PR - it will be closed when it becomes a part of #56345.

Dylan-DPC-zz · 2018-12-10T10:43:55Z

Thanks. Marking it as blocked.

bors · 2019-02-13T02:04:35Z

☔ The latest upstream changes (presumably #58051) made this pull request unmergeable. Please resolve the merge conflicts.

Centril · 2019-02-23T04:57:27Z

Closing meanwhile.

str: common logic for replace & replacen

9259367

rust-highfive assigned kennytm Dec 3, 2018

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Dec 3, 2018

Centril suggested changes Dec 3, 2018

View reviewed changes

Dylan-DPC-zz added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Dec 10, 2018

Dylan-DPC-zz added S-blocked Status: Marked as blocked ❌ on something else such as an RFC or other implementation work. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Dec 10, 2018

Centril added S-blocked-closed and removed S-blocked Status: Marked as blocked ❌ on something else such as an RFC or other implementation work. labels Feb 23, 2019

Centril closed this Feb 23, 2019

ljedrz deleted the common_str_replace_logic branch June 24, 2019 19:05

jyn514 added S-blocked Status: Marked as blocked ❌ on something else such as an RFC or other implementation work. and removed S-blocked-closed labels Mar 10, 2021

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str: common logic for replace & replacen #56464

str: common logic for replace & replacen #56464

ljedrz commented Dec 3, 2018

rust-highfive commented Dec 3, 2018

kennytm commented Dec 3, 2018

ljedrz commented Dec 3, 2018

kennytm commented Dec 3, 2018

rust-highfive commented Dec 3, 2018

Centril Dec 3, 2018

Centril Dec 3, 2018

Centril Dec 3, 2018

Dylan-DPC-zz commented Dec 10, 2018

ljedrz commented Dec 10, 2018

Dylan-DPC-zz commented Dec 10, 2018

bors commented Feb 13, 2019

Centril commented Feb 23, 2019

str: common logic for replace & replacen #56464

str: common logic for replace & replacen #56464

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ljedrz commented Dec 3, 2018

rust-highfive commented Dec 3, 2018

kennytm commented Dec 3, 2018

ljedrz commented Dec 3, 2018

kennytm commented Dec 3, 2018

rust-highfive commented Dec 3, 2018

Centril Dec 3, 2018

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Centril Dec 3, 2018

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Centril Dec 3, 2018

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Dylan-DPC-zz commented Dec 10, 2018

ljedrz commented Dec 10, 2018

Dylan-DPC-zz commented Dec 10, 2018

bors commented Feb 13, 2019

Centril commented Feb 23, 2019