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encoding/gob: make integers encoding faster

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name                old time/op  new time/op  delta
EncodeInt32Slice-4  14.6µs ± 2%  12.2µs ± 1%  -16.65%  (p=0.000 n=19+18)

Change-Id: I078a171f1633ff81d7e3f981dc9a398309ecb2c0
Reviewed-on: https://go-review.googlesource.com/38269
Reviewed-by: Rob Pike <r@golang.org>
This commit is contained in:
Alberto Donizetti 2017-03-17 18:42:58 +01:00 committed by Rob Pike
parent 42e97468a1
commit ed00cd94f2
2 changed files with 9 additions and 9 deletions
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16
src/encoding/gob/encode.go
View File

@ -8,7 +8,9 @@ package gob
import (
"encoding"
"encoding/binary"
"math"
"math/bits"
"reflect"
"sync"
)
@ -107,14 +109,12 @@ func (state *encoderState) encodeUint(x uint64) {
state.b.WriteByte(uint8(x))
return
}
i := uint64Size
for x > 0 {
state.buf[i] = uint8(x)
x >>= 8
i--
}
state.buf[i] = uint8(i - uint64Size) // = loop count, negated
state.b.Write(state.buf[i : uint64Size+1])
binary.BigEndian.PutUint64(state.buf[1:], x)
bc := bits.LeadingZeros64(x) >> 3 // 8 - bytelen(x)
state.buf[bc] = uint8(bc - uint64Size) // and then we subtract 8 to get -bytelen(x)
state.b.Write(state.buf[bc : uint64Size+1])
}
// encodeInt writes an encoded signed integer to state.w.

2
src/encoding/gob/timing_test.go
View File

@ -171,7 +171,7 @@ func BenchmarkEncodeInt32Slice(b *testing.B) {
enc := NewEncoder(&buf)
a := make([]int32, 1000)
for i := range a {
a[i] = 1234
a[i] = int32(i * 100)
}
b.ResetTimer()
for i := 0; i < b.N; i++ {