delta/go-git.git/src/bytes, branch dev.cmdgo

bytes, strings: optimize Trim for single byte cutsets

2021-08-25T19:29:15+00:00

Using the latest version of all modules known by the module proxy,
we determine that for all Trim usages (and related functionality):
* 76.6% have cutsets of len=1, and
* 13.4% have cutsets of len=2.

Given that a vast majority of usages only have a cutset of len=1,
we should more heavily optimize for that situation.
Previously, there was some optimization for cutsets of len=1,
but it's within the internal makeCutsetFunc function.
This is sub-optimal as it incurs an allocation in makeCutsetFunc
for the closure over that single byte.

This CL removes special-casing of one-byte cutsets from makeCutsetFunc
and instead distributes it directly in Trim, TrimRight, and TrimLeft.
Whether we should distribute the entire ASCII cutset logic into Trim
is a future CL that should be discussed and handled separately.
The evidence for multibyte cutsets is not as obviously compelling.

name                old time/op  new time/op  delta
bytes/TrimByte-4    84.1ns ± 2%   7.5ns ± 1%  -91.10%  (p=0.000 n=9+7)
strings/TrimByte-4  86.2ns ± 3%   8.3ns ± 1%  -90.33%  (p=0.000 n=9+10)

Fixes #46446

Change-Id: Ia0e31a8384c3ce111ae35465605bcec45df2ebec
Reviewed-on: https://go-review.googlesource.com/c/go/+/323318
Trust: Joe Tsai 
Run-TryBot: Joe Tsai 
Reviewed-by: Brad Fitzpatrick 
TryBot-Result: Go Bot

bytes: correct tense in comment

2021-03-15T17:37:09+00:00

Undo incorrect change accidentally made in CL 299109.

Change-Id: Iba29827d0fbd3637c311cebc50c2f4ea437fc582
Reviewed-on: https://go-review.googlesource.com/c/go/+/301830
Trust: Ian Lance Taylor 
Reviewed-by: Tobias Klauser

all: remove duplicate words

2021-03-13T11:56:59+00:00

Change-Id: Ib0469232a2b69a869e58d5d24990ad74ac96ea56
GitHub-Last-Rev: eb38e049ee1e773392ff3747e1eb2af20dd50dcd
GitHub-Pull-Request: golang/go#44805
Reviewed-on: https://go-review.googlesource.com/c/go/+/299109
Trust: Emmanuel Odeke 
Run-TryBot: Emmanuel Odeke 
TryBot-Result: Go Bot 
Reviewed-by: Bryan C. Mills

bufio, bytes, strings: handle negative runes in WriteRune

2021-02-24T04:01:25+00:00

Updates #43254

Change-Id: I7d4bf3b99cc36ca2156af5bb01a1c595419d1d3c
Reviewed-on: https://go-review.googlesource.com/c/go/+/280492
Reviewed-by: Emmanuel Odeke 
Reviewed-by: Rob Pike 
Trust: Emmanuel Odeke 
Run-TryBot: Emmanuel Odeke 
TryBot-Result: Go Bot

all: go fmt std cmd (but revert vendor)

2021-02-20T03:54:50+00:00

Make all our package sources use Go 1.17 gofmt format
(adding //go:build lines).

Part of //go:build change (#41184).
See https://golang.org/design/draft-gobuild

Change-Id: Ia0534360e4957e58cd9a18429c39d0e32a6addb4
Reviewed-on: https://go-review.googlesource.com/c/go/+/294430
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Jason A. Donenfeld 
Reviewed-by: Ian Lance Taylor

bytes: add example for (*Buffer).Bytes

2020-11-11T20:51:00+00:00

Change-Id: I49ac604530fff7928fa15de07563418b104da5e4
Reviewed-on: https://go-review.googlesource.com/c/go/+/268260
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Go Bot 
Reviewed-by: Ian Lance Taylor 
Trust: Giovanni Bajo

all: update references to symbols moved from io/ioutil to io

2020-10-20T18:41:18+00:00

The old ioutil references are still valid, but update our code
to reflect best practices and get used to the new locations.

Code compiled with the bootstrap toolchain
(cmd/asm, cmd/dist, cmd/compile, debug/elf)
must remain Go 1.4-compatible and is excluded.
Also excluded vendored code.

For #41190.

Change-Id: I6d86f2bf7bc37a9d904b6cee3fe0c7af6d94d5b1
Reviewed-on: https://go-review.googlesource.com/c/go/+/263142
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Emmanuel Odeke

bytes, internal/bytealg: fix incorrect IndexString usage

2020-09-23T19:55:33+00:00

The IndexString implementation in the bytealg package requires that
the string passed into it be in the range '2 <= len(s) <= MaxLen'
where MaxLen may be any value (including 0).

CL 156998 added calls to bytealg.IndexString where MaxLen was not
first checked. This led to an illegal instruction on s390x with
the vector facility disabled.

This CL guards the calls to bytealg.IndexString with a MaxLen check.
If the check fails then the code now falls back to the pre CL 156998
implementation (a loop over the runes in the string).

Since the MaxLen check is now in place the generic implementation is
no longer called so I have returned it to its original unimplemented
state.

In future we may want to drop MaxLen to prevent this kind of
confusion.

Fixes #41552.

Change-Id: Ibeb3f08720444a05c08d719ed97f6cef2423bbe9
Reviewed-on: https://go-review.googlesource.com/c/go/+/256717
Run-TryBot: Michael Munday 
TryBot-Result: Go Bot 
Trust: Michael Munday 
Reviewed-by: Keith Randall

bytes: simpler and faster FieldsFunc (apply same changes as for strings)

2020-05-01T03:49:21+00:00

This change applies the recent changes to the strings package
(https://golang.org/cl/229765) to this package, with relevant
local adjustments.

In contrast to the changes in strings, for the bytes package
this change leads to a nice performance improvement of >10%.

Benchmarks run on a "quiet" MacBook Pro, 3.3GHz Dual-Core Intel Core i7,
with 16GB 2133MHz LPDDR3 RAM running macOS 10.15.4.

name                        old time/op    new time/op     delta
FieldsFunc/ASCII/16-4          191ns ± 9%      163ns ± 2%  -14.66%  (p=0.008 n=5+5)
FieldsFunc/ASCII/256-4        2.08µs ± 5%     1.80µs ± 8%  -13.51%  (p=0.008 n=5+5)
FieldsFunc/ASCII/4096-4       36.1µs ± 2%     31.7µs ± 7%  -12.34%  (p=0.008 n=5+5)
FieldsFunc/ASCII/65536-4       584µs ± 3%      517µs ± 3%  -11.52%  (p=0.008 n=5+5)
FieldsFunc/ASCII/1048576-4    9.45ms ± 3%     8.11ms ± 8%  -14.19%  (p=0.008 n=5+5)
FieldsFunc/Mixed/16-4          202ns ± 2%      181ns ± 2%  -10.02%  (p=0.008 n=5+5)
FieldsFunc/Mixed/256-4        2.12µs ± 6%     1.78µs ± 3%  -16.16%  (p=0.008 n=5+5)
FieldsFunc/Mixed/4096-4       40.4µs ± 2%     36.1µs ± 1%  -10.66%  (p=0.008 n=5+5)
FieldsFunc/Mixed/65536-4       700µs ± 5%      612µs ± 1%  -12.59%  (p=0.008 n=5+5)
FieldsFunc/Mixed/1048576-4    11.2ms ± 8%     10.3ms ± 4%   -8.15%  (p=0.008 n=5+5)

name                        old speed      new speed       delta
FieldsFunc/ASCII/16-4       84.0MB/s ± 9%   98.3MB/s ± 2%  +17.04%  (p=0.008 n=5+5)
FieldsFunc/ASCII/256-4       123MB/s ± 5%    143MB/s ± 8%  +15.74%  (p=0.008 n=5+5)
FieldsFunc/ASCII/4096-4      113MB/s ± 2%    130MB/s ± 6%  +14.20%  (p=0.008 n=5+5)
FieldsFunc/ASCII/65536-4     112MB/s ± 2%    127MB/s ± 3%  +13.05%  (p=0.008 n=5+5)
FieldsFunc/ASCII/1048576-4   111MB/s ± 3%    130MB/s ± 8%  +16.66%  (p=0.008 n=5+5)
FieldsFunc/Mixed/16-4       79.3MB/s ± 2%   88.2MB/s ± 2%  +11.15%  (p=0.008 n=5+5)
FieldsFunc/Mixed/256-4       121MB/s ± 5%    144MB/s ± 3%  +19.19%  (p=0.008 n=5+5)
FieldsFunc/Mixed/4096-4      101MB/s ± 2%    113MB/s ± 1%  +11.92%  (p=0.008 n=5+5)
FieldsFunc/Mixed/65536-4    93.7MB/s ± 5%  107.1MB/s ± 1%  +14.31%  (p=0.008 n=5+5)
FieldsFunc/Mixed/1048576-4  93.6MB/s ± 8%  101.8MB/s ± 4%   +8.77%  (p=0.008 n=5+5)

name                        old alloc/op   new alloc/op    delta
FieldsFunc/ASCII/16-4          80.0B ± 0%      80.0B ± 0%     ~     (all equal)
FieldsFunc/ASCII/256-4          768B ± 0%       768B ± 0%     ~     (all equal)
FieldsFunc/ASCII/4096-4       24.8kB ± 0%     24.8kB ± 0%     ~     (all equal)
FieldsFunc/ASCII/65536-4       497kB ± 0%      497kB ± 0%     ~     (p=0.444 n=5+5)
FieldsFunc/ASCII/1048576-4    9.61MB ± 0%     9.61MB ± 0%     ~     (p=0.500 n=5+5)
FieldsFunc/Mixed/16-4          96.0B ± 0%      96.0B ± 0%     ~     (all equal)
FieldsFunc/Mixed/256-4          768B ± 0%       768B ± 0%     ~     (all equal)
FieldsFunc/Mixed/4096-4       24.8kB ± 0%     24.8kB ± 0%     ~     (all equal)
FieldsFunc/Mixed/65536-4       497kB ± 0%      497kB ± 0%     ~     (all equal)
FieldsFunc/Mixed/1048576-4    9.61MB ± 0%     9.61MB ± 0%     ~     (p=0.881 n=5+5)

name                        old allocs/op  new allocs/op   delta
FieldsFunc/ASCII/16-4           1.00 ± 0%       1.00 ± 0%     ~     (all equal)
FieldsFunc/ASCII/256-4          1.00 ± 0%       1.00 ± 0%     ~     (all equal)
FieldsFunc/ASCII/4096-4         5.00 ± 0%       5.00 ± 0%     ~     (all equal)
FieldsFunc/ASCII/65536-4        12.0 ± 0%       12.0 ± 0%     ~     (all equal)
FieldsFunc/ASCII/1048576-4      24.0 ± 0%       24.0 ± 0%     ~     (all equal)
FieldsFunc/Mixed/16-4           1.00 ± 0%       1.00 ± 0%     ~     (all equal)
FieldsFunc/Mixed/256-4          1.00 ± 0%       1.00 ± 0%     ~     (all equal)
FieldsFunc/Mixed/4096-4         5.00 ± 0%       5.00 ± 0%     ~     (all equal)
FieldsFunc/Mixed/65536-4        12.0 ± 0%       12.0 ± 0%     ~     (all equal)
FieldsFunc/Mixed/1048576-4      24.0 ± 0%       24.0 ± 0%     ~     (all equal)

Change-Id: I59a2ed52563851c693b2c8dfce7e3cde640f62a9
Reviewed-on: https://go-review.googlesource.com/c/go/+/231120
Reviewed-by: Ian Lance Taylor

bytes, strings: align requirements for functions passed to FieldFuncs

2020-04-29T19:58:47+00:00

golang.org/cl/229763 removed the documentation of requirements of
the function passed to FieldsFunc. The current implementation does
not require functions to return consistent results but this had not
been the case for previous implementations.

Add the requirement for consistent results back to the documentation
to allow for future implementations to be more allocation efficient
for an output with more than 32 fields. This is possible with a two
pass algorithm first determining the number of fields used to allocate
the output slice and then splitting the input into fields.

While at it align the documentation of bytes.FieldsFunc with
strings.FieldFunc.

Fixes #38630

Change-Id: Iabbf9ca3dff0daa41f4ec930a21a3dd98e19f122
Reviewed-on: https://go-review.googlesource.com/c/go/+/230797
Run-TryBot: Martin Möhrmann 
TryBot-Result: Gobot Gobot 
Reviewed-by: Robert Griesemer