Optimize/new route regexp allocations

[titpetric]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

This optimizes NewRouter creation. The change introduces strings.Builder for more efficient strings concatenation, and replaces SplitN with Index, avoiding the allocations for the slice.

Related Tickets & Documents

# go test -bench=NewRouter -benchmem -memprofile memprofile.out -cpuprofile profile.out -count 10
goos: linux
goarch: amd64
pkg: github.com/gorilla/mux
cpu: 11th Gen Intel(R) Core(TM) i7-1185G7 @ 3.00GHz
BenchmarkNewRouter-8             	   49730	     32679 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   44238	     32534 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   38658	     29237 ns/op	   25576 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   36507	     34312 ns/op	   25578 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   32928	     37220 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   32894	     42599 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   32104	     33482 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   27852	     37150 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   28695	     40131 ns/op	   25580 B/op	     343 allocs/op
BenchmarkNewRouter-8             	   35971	     36103 ns/op	   25577 B/op	     343 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  461474	      2702 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  397422	      2639 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  488200	      2496 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  594357	      2891 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  532392	      2602 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  487236	      2535 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  512724	      3118 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  397882	      2704 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  364755	      2881 ns/op	    1424 B/op	      42 allocs/op
BenchmarkNewRouterRegexpFunc-8   	  616176	      2580 ns/op	    1424 B/op	      42 allocs/op
PASS
ok  	github.com/gorilla/mux	36.247s

Added/updated tests?

• Yes

Run verifications and test

• make verify is passing
• make test is passing

[codecov]

Codecov Report

Attention: Patch coverage is 90.90909% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 78.18%. Comparing base (7d9a6f7) to head (f80a252).

❗ Current head f80a252 differs from pull request most recent head ed62916. Consider uploading reports for the commit ed62916 to get more accurate results

Files	Patch %	Lines
regexp.go	90.62%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #732      +/-   ##
==========================================
- Coverage   79.58%   78.18%   -1.40%     
==========================================
  Files           5        5              
  Lines         911      903       -8     
==========================================
- Hits          725      706      -19     
- Misses        131      141      +10     
- Partials       55       56       +1     

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[titpetric]

Rebased off #731

[titpetric]

@AlexVulaj thanks for #731 merge; rebased this one for review. Benchmark still the same as in description.

[titpetric]

@coreydaley is there anything i can/should do to get this reviewed?

[apoorvajagtap]

Suggested change

	return nil, fmt.Errorf("mux: missing name or pattern in %q", param)
	return nil, fmt.Errorf("mux: missing name or pattern in %q", tpl[idxs[i]:end])

Having param as the variable might not help much, as when there's no pattern or name inside braces {}, param will just return an empty string (""), whereas. Above will at least help with the braces for reference.

[titpetric]

Gotcha, so {} would be printed as well. Sounds legit, I'll give it a once over and add a test, some inline comments, it's a bit hard to read after some time since writing it

[apoorvajagtap]

Hi @titpetric, thanks for working on this!
Also, thanks for being patient while we were adapting to the changes :). I have looked through & added some inputs, please feel free to share your thoughts.