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encoding/base64: optimize decodemap memory set

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The existing implementation has an execution time higher in the benchmark than this one.
This is an optimized implementation using the copy() function and a constant 256 bytes string with the values to be copied.

```
name           old time/op    new time/op    delta
NewEncoding-4     329ns ± 1%     231ns ± 1%  -29.72%  (p=0.008 n=5+5)

name           old speed      new speed      delta
NewEncoding-4   778MB/s ± 1%  1108MB/s ± 1%  +42.29%  (p=0.008 n=5+5)
```

Fixes #53211

Change-Id: I80fe62aa40623125ef81ae9164a8405eed30b71b
GitHub-Last-Rev: 55dce6f636
GitHub-Pull-Request: golang/go#53212
Reviewed-on: https://go-review.googlesource.com/c/go/+/410194
Reviewed-by: Keith Randall <khr@google.com>
Run-TryBot: Keith Randall <khr@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Auto-Submit: Keith Randall <khr@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
This commit is contained in:
ErikPelli 2022-08-14 07:46:22 +00:00 committed by Gopher Robot
parent 0d8efa6e84
commit e1b62efaf3
3 changed files with 51 additions and 11 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

27
src/encoding/base32/base32.go
View file

@ -25,8 +25,25 @@ type Encoding struct {
}
const (
StdPadding rune = '=' // Standard padding character
NoPadding rune = -1 // No padding
StdPadding rune = '=' // Standard padding character
NoPadding rune = -1 // No padding
decodeMapInitialize = "" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
)
const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567"
@ -40,12 +57,10 @@ func NewEncoding(encoder string) *Encoding {
}
e := new(Encoding)
copy(e.encode[:], encoder)
e.padChar = StdPadding
copy(e.encode[:], encoder)
copy(e.decodeMap[:], decodeMapInitialize)
for i := 0; i < len(e.decodeMap); i++ {
e.decodeMap[i] = 0xFF
}
for i := 0; i < len(encoder); i++ {
e.decodeMap[encoder[i]] = byte(i)
}

25
src/encoding/base64/base64.go
View file

@ -28,8 +28,25 @@ type Encoding struct {
}
const (
StdPadding rune = '=' // Standard padding character
NoPadding rune = -1 // No padding
StdPadding rune = '=' // Standard padding character
NoPadding rune = -1 // No padding
decodeMapInitialize = "" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff" +
"\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff"
)
const encodeStd = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
@ -53,10 +70,8 @@ func NewEncoding(encoder string) *Encoding {
e := new(Encoding)
e.padChar = StdPadding
copy(e.encode[:], encoder)
copy(e.decodeMap[:], decodeMapInitialize)
for i := 0; i < len(e.decodeMap); i++ {
e.decodeMap[i] = 0xFF
}
for i := 0; i < len(encoder); i++ {
e.decodeMap[encoder[i]] = byte(i)
}

10
src/encoding/base64/base64_test.go
View file

@ -504,6 +504,16 @@ func BenchmarkDecodeString(b *testing.B) {
}
}
func BenchmarkNewEncoding(b *testing.B) {
b.SetBytes(int64(len(Encoding{}.decodeMap)))
for i := 0; i < b.N; i++ {
e := NewEncoding(encodeStd)
for _, v := range e.decodeMap {
_ = v
}
}
}
func TestDecoderRaw(t *testing.T) {
source := "AAAAAA"
want := []byte{0, 0, 0, 0}