delta/go-git.git/src/strings/strings.go, branch dev.inline

bytes, strings: optimize for ASCII sets

2016-10-28T17:37:04+00:00

In a large codebase within Google, there are thousands of uses of:
	ContainsAny|IndexAny|LastIndexAny|Trim|TrimLeft|TrimRight

An analysis of their usage shows that over 97% of them only use character
sets consisting of only ASCII symbols.

Uses of ContainsAny|IndexAny|LastIndexAny:
	 6% are 1   character  (e.g., "\n" or " ")
	58% are 2-4 characters (e.g., "<>" or "\r\n\t ")
	24% are 5-9 characters (e.g., "()[]*^$")
	10% are 10+ characters (e.g., "+-=&|>
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick 
Reviewed-by: Martin Möhrmann

bytes, strings: fix regression in IndexRune

2016-10-26T23:02:27+00:00

In all previous versions of Go, the behavior of IndexRune(s, r)
where r was utf.RuneError was that it would effectively return the
index of any invalid UTF-8 byte sequence (include RuneError).
Optimizations made in http://golang.org/cl/28537 and
http://golang.org/cl/28546 altered this undocumented behavior such
that RuneError would only match on the RuneError rune itself.

Although, the new behavior is arguably reasonable, it did break code
that depended on the previous behavior. Thus, we add special checks
to ensure that we preserve the old behavior.

There is a slight performance hit for correctness:
	benchmark                   old ns/op     new ns/op     delta
	BenchmarkIndexRune/10-4     19.3          21.6          +11.92%
	BenchmarkIndexRune/32-4     33.6          35.2          +4.76%
This only occurs on small strings. The performance hit for larger strings
is neglible and not shown.

Fixes #17611

Change-Id: I1d863a741213d46c40b2e1724c41245df52502a5
Reviewed-on: https://go-review.googlesource.com/32123
Run-TryBot: Joe Tsai 
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick

bytes, strings: fix snake-case in variable name

2016-10-26T21:51:48+00:00

Change-Id: I40896fffbffefa359d08abda346933aa996f628d
Reviewed-on: https://go-review.googlesource.com/32124
Reviewed-by: Brad Fitzpatrick 
Run-TryBot: Brad Fitzpatrick 
TryBot-Result: Gobot Gobot

strings: use Index in Count

2016-10-15T16:39:31+00:00

This simplifies code and provides performance iprovments:
Similar to https://go-review.googlesource.com/#/c/28577

CountHard1-48               1.74ms ±14%  0.17ms ±14%  -90.16%  (p=0.000 n=19+19)
CountHard2-48               1.78ms ±15%  0.25ms ±13%  -86.10%  (p=0.000 n=19+20)
CountHard3-48               1.78ms ±12%  0.80ms ±11%  -55.19%  (p=0.000 n=17+20)
CountTorture-48             13.5µs ±14%  13.6µs ±11%     ~     (p=0.625 n=18+19)
CountTortureOverlapping-48  6.92ms ±13%  8.42ms ±11%  +21.72%  (p=0.000 n=19+17)

Change-Id: Ief120aee918a66487c76be56e0796871c8502f89
Reviewed-on: https://go-review.googlesource.com/28586
Run-TryBot: Ilya Tocar 
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick

strings, bytes: panic if Repeat overflows or if given a negative count

2016-10-01T15:47:35+00:00

Panic if Repeat is given a negative count or
if the value of (len(*) * count) is detected
to overflow.
We panic because we cannot change the
signature of Repeat to return an error.

Fixes #16237

Change-Id: I9f5ba031a5b8533db0582d7a672ffb715143f3fb
Reviewed-on: https://go-review.googlesource.com/29954
Run-TryBot: Brad Fitzpatrick 
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick

strings: make IndexRune faster

2016-09-07T01:03:10+00:00

re-implement IndexRune by Index which is well optimized to get
performance gain.

name                   old time/op  new time/op  delta
IndexRune-4            30.2ns ± 1%  28.3ns ± 1%   -6.22%  (p=0.000 n=20+19)
IndexRuneLongString-4   156ns ± 1%    49ns ± 1%  -68.72%  (p=0.000 n=19+19)
IndexRuneFastPath-4    10.6ns ± 2%  10.0ns ± 1%   -6.30%  (p=0.000 n=18+18)

Change-Id: Ie663b8f7860ca51892dd4be182fca3caa5f8ae61
Reviewed-on: https://go-review.googlesource.com/28546
Reviewed-by: Brad Fitzpatrick 
Run-TryBot: Brad Fitzpatrick 
TryBot-Result: Gobot Gobot

strings: add special cases for Join of 2 and 3 strings

2016-08-16T00:33:15+00:00

We already had special cases for 0 and 1. Add 2 and 3 for now too.
To be removed if the compiler is improved later (#6714).

This halves the number of allocations and total bytes allocated via
common filepath.Join calls, improving filepath.Walk performance.

Noticed as part of investigating filepath.Walk in #16399.

Change-Id: If7b1bb85606d4720f3ebdf8de7b1e12ad165079d
Reviewed-on: https://go-review.googlesource.com/25005
Reviewed-by: Ian Lance Taylor 
Run-TryBot: Brad Fitzpatrick

strings: improve explode and correct comment

2016-04-13T04:54:03+00:00

Merges explodetests into splittests which already contain
some of the tests that cover explode.

Adds a test to cover the utf8.RuneError branch in explode.

name      old time/op  new time/op  delta
Split1-2  14.9ms ± 0%  14.2ms ± 0%  -4.06%  (p=0.000 n=47+49)

Change-Id: I00f796bd2edab70e926ea9e65439d820c6a28254
Reviewed-on: https://go-review.googlesource.com/21609
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor

all: single space after period.

2016-03-02T00:13:47+00:00

The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.

This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:

$ perl -i -npe 's,^(\s*// .+[a-z]\.)  +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.)  +([A-Z])')
$ go test go/doc -update

Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike 
Reviewed-by: Dave Day 
Run-TryBot: Brad Fitzpatrick 
TryBot-Result: Gobot Gobot

strings: add asm version of Index() for short strings on amd64

2015-11-03T16:04:28+00:00

Currently we have special case for 1-byte strings,
This extends this to strings shorter than 32 bytes on amd64.
Results (broadwell):

name                 old time/op  new time/op  delta
IndexRune-4          57.4ns ± 0%  57.5ns ± 0%   +0.10%        (p=0.000 n=20+19)
IndexRuneFastPath-4  20.4ns ± 0%  20.4ns ± 0%     ~     (all samples are equal)
Index-4              21.0ns ± 0%  21.8ns ± 0%   +3.81%        (p=0.000 n=20+20)
LastIndex-4          7.07ns ± 1%  6.98ns ± 0%   -1.21%        (p=0.000 n=20+16)
IndexByte-4          18.3ns ± 0%  18.3ns ± 0%     ~     (all samples are equal)
IndexHard1-4         1.46ms ± 0%  0.39ms ± 0%  -73.06%        (p=0.000 n=16+16)
IndexHard2-4         1.46ms ± 0%  0.30ms ± 0%  -79.55%        (p=0.000 n=18+18)
IndexHard3-4         1.46ms ± 0%  0.66ms ± 0%  -54.68%        (p=0.000 n=19+19)
LastIndexHard1-4     1.46ms ± 0%  1.46ms ± 0%   -0.01%        (p=0.036 n=18+20)
LastIndexHard2-4     1.46ms ± 0%  1.46ms ± 0%     ~           (p=0.588 n=19+19)
LastIndexHard3-4     1.46ms ± 0%  1.46ms ± 0%     ~           (p=0.283 n=17+20)
IndexTorture-4       11.1µs ± 0%  11.1µs ± 0%   +0.01%        (p=0.000 n=18+17)

Change-Id: I892781549f558f698be4e41f9f568e3d0611efb5
Reviewed-on: https://go-review.googlesource.com/16430
Reviewed-by: Keith Randall 
Run-TryBot: Ilya Tocar