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debug/dwarf: optimize buf.string

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(*buf).string previously manually searched
through its underlying byte slice until we
encountered a '0'. This change instead uses
bytes.IndexByte that results in a speed up:

$ benchstat before.txt after.txt

name         old time/op    new time/op    delta
BufString-8     257ns ± 1%     174ns ± 1%  -32.37%  (p=0.000 n=9+8)

name         old speed      new speed      delta
BufString-8   495MB/s ± 1%   732MB/s ± 1%  +47.76%  (p=0.000 n=10+8)

name         old alloc/op   new alloc/op   delta
BufString-8      162B ± 0%      162B ± 0%     ~     (all equal)

name         old allocs/op  new allocs/op  delta
BufString-8      3.00 ± 0%      3.00 ± 0%     ~     (all equal)

Change-Id: I7cf241742cc091d5d30d987a168b02d83955b1cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/196657
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
This commit is contained in:
Emmanuel T Odeke 2019-09-19 23:35:34 -07:00 committed by Emmanuel Odeke
parent bb0a8fd38f
commit 0d9981bccb
1 changed files with 10 additions and 9 deletions
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19
src/debug/dwarf/buf.go
View File

@ -7,6 +7,7 @@
package dwarf
import (
"bytes"
"encoding/binary"
"strconv"
)
@ -79,16 +80,16 @@ func (b *buf) bytes(n int) []byte {
func (b *buf) skip(n int) { b.bytes(n) }
func (b *buf) string() string {
for i := 0; i < len(b.data); i++ {
if b.data[i] == 0 {
s := string(b.data[0:i])
b.data = b.data[i+1:]
b.off += Offset(i + 1)
return s
}
i := bytes.IndexByte(b.data, 0)
if i < 0 {
b.error("underflow")
return ""
}
b.error("underflow")
return ""
s := string(b.data[0:i])
b.data = b.data[i+1:]
b.off += Offset(i + 1)
return s
}
func (b *buf) uint16() uint16 {