8291598: Matcher.appendReplacement should not create new StringBuilder instances #13048

rgiulietti · 2023-03-15T18:15:02Z

Remove instantiation of StringBuilder

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JDK-8291598: Matcher.appendReplacement should not create new StringBuilder instances

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Roger Riggs (@RogerRiggs - Reviewer)

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…r instances

bridgekeeper · 2023-03-15T18:16:08Z

👋 Welcome back rgiulietti! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

openjdk · 2023-03-15T18:19:32Z

@rgiulietti The following label will be automatically applied to this pull request:

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rgiulietti · 2023-03-15T18:21:46Z

Benchmark for the example in the documentation for Matcher.appendReplacement()

before

Benchmark                                Mode  Cnt    Score   Error  Units
AppendReplacement.testAppendReplacement  avgt   15  177.029 ± 6.294  ns/op

after

Benchmark                                Mode  Cnt    Score   Error  Units
AppendReplacement.testAppendReplacement  avgt   15  142.373 ± 1.684  ns/op

Same example, but with pattern "(cat)" (1 capturing group), matcher on the input repeated 1000 times, and replacement string "$1dog$1cat$1mouse" (3 back references).

before

Benchmark                                Mode  Cnt       Score      Error  Units
AppendReplacement.testAppendReplacement  avgt   15  262576.335 ± 3718.905  ns/op

after

Benchmark                                Mode  Cnt       Score     Error  Units
AppendReplacement.testAppendReplacement  avgt   15  225700.642 ± 683.721  ns/op

mlbridge · 2023-03-15T18:24:56Z

Webrevs

…r instances Fix copyright year

RogerRiggs · 2023-03-15T18:55:35Z

src/java.base/share/classes/java/util/regex/Matcher.java

+                        StringBuilder gsb = new StringBuilder();
+                        while (cursor < replacement.length()) {
+                            nextChar = replacement.charAt(cursor);
+                            if (ASCII.isLower(nextChar) ||
+                                    ASCII.isUpper(nextChar) ||
+                                    ASCII.isDigit(nextChar)) {
+                                gsb.append(nextChar);
+                                cursor++;
+                            } else {
+                                break;
+                            }


Possibly remove another SB allocation; remember start and end and use replacement.substring(start, end).

Thanks @RogerRiggs, addressed in latest commit.

…r instances Removed other allocations of StringBuilder when processing named groups in replacement string.

rgiulietti · 2023-03-28T11:54:15Z

Waiting for other comments and review

RogerRiggs

Sorry for the delay.
The workaround for appending to StringBuffer/StringBuilder is awkward, adding a try/catch that can't happen. But I don't have a better suggestion.
It is scoped to the appendExpandedReplacement method and has no runtime impact.

openjdk · 2023-03-28T17:37:05Z

@rgiulietti This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8291598: Matcher.appendReplacement should not create new StringBuilder instances

Reviewed-by: rriggs

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 156 new commits pushed to the master branch:

fab2357: 8304498: JShell does not switch to raw mode when there is no /bin/test
1fc218c: 8303912: Clean up JavadocTokenizer
c1f5ca1: 8303623: Compiler should disallow non-standard UTF-8 string encodings
695683b: 8304880: [PPC64] VerifyOops code in C1 doesn't work with ZGC
83ce65e: 8305004: add @SPEC tags to langtools modules
32ef452: 8304884: Update Bytecodes data to be mostly compile time constants
927e674: 8300977: Retire java.io.ExpiringCache
c90699e: 8304989: unnecessary dash in @param gives double-dash in docs
395a4ce: 8304591: (fs) UnixPath.stringValue need not be volatile
60640a2: 8300979: Lazily initialize (byte, char)arr in java.io.DataInputStream
... and 146 more: https://git.openjdk.org/jdk/compare/e3777b0c49abb9cc1925f4044392afadf3adef61...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

rgiulietti · 2023-03-28T17:53:58Z

@RogerRiggs Yes, it would be nice to be able to write

private void appendExpandedReplacement(StringBuilder | StringBuffer app, String replacement)

and get rid of the try statement altogether.

rgiulietti · 2023-03-28T17:54:28Z

/integrate

openjdk · 2023-03-28T17:55:33Z

Going to push as commit ca745cb.
Since your change was applied there have been 157 commits pushed to the master branch:

1683a63: 8305098: [Backout] JDK-8303912 Clean up JavadocTokenizer
fab2357: 8304498: JShell does not switch to raw mode when there is no /bin/test
1fc218c: 8303912: Clean up JavadocTokenizer
c1f5ca1: 8303623: Compiler should disallow non-standard UTF-8 string encodings
695683b: 8304880: [PPC64] VerifyOops code in C1 doesn't work with ZGC
83ce65e: 8305004: add @SPEC tags to langtools modules
32ef452: 8304884: Update Bytecodes data to be mostly compile time constants
927e674: 8300977: Retire java.io.ExpiringCache
c90699e: 8304989: unnecessary dash in @param gives double-dash in docs
395a4ce: 8304591: (fs) UnixPath.stringValue need not be volatile
... and 147 more: https://git.openjdk.org/jdk/compare/e3777b0c49abb9cc1925f4044392afadf3adef61...master

Your commit was automatically rebased without conflicts.

openjdk · 2023-03-28T17:55:48Z

@rgiulietti Pushed as commit ca745cb.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

8291598: Matcher.appendReplacement should not create new StringBuilde…

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…r instances

openjdk bot added the rfr Pull request is ready for review label Mar 15, 2023

openjdk bot added the core-libs core-libs-dev@openjdk.org label Mar 15, 2023

8291598: Matcher.appendReplacement should not create new StringBuilde…

c9432a6

…r instances Fix copyright year

RogerRiggs reviewed Mar 15, 2023

View reviewed changes

8291598: Matcher.appendReplacement should not create new StringBuilde…

4b5ac59

…r instances Removed other allocations of StringBuilder when processing named groups in replacement string.

RogerRiggs approved these changes Mar 28, 2023

View reviewed changes

openjdk bot added the ready Pull request is ready to be integrated label Mar 28, 2023

openjdk bot added the integrated Pull request has been integrated label Mar 28, 2023

openjdk bot closed this Mar 28, 2023

openjdk bot removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Mar 28, 2023

rgiulietti deleted the JDK-8291598 branch March 29, 2023 12:46

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8291598: Matcher.appendReplacement should not create new StringBuilder instances #13048

8291598: Matcher.appendReplacement should not create new StringBuilder instances #13048

rgiulietti commented Mar 15, 2023 •

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8291598: Matcher.appendReplacement should not create new StringBuilder instances #13048

8291598: Matcher.appendReplacement should not create new StringBuilder instances #13048

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