qbit/go
1
0
Fork 0
mirror of https://github.com/golang/go synced 2024-11-21 17:54:39 -07:00
Code Releases Activity

go/scanner: faster scanning

Browse Source 
Optimize some common cases.

benchmark            old ns/op    new ns/op    delta
BenchmarkScanFile       718907       667960   -7.09%

benchmark             old MB/s     new MB/s  speedup
BenchmarkScanFile        23.03        25.51    1.11x

R=r
CC=golang-dev
https://golang.org/cl/6454150
This commit is contained in:
Robert Griesemer 2012-08-14 11:26:30 -07:00
parent 7fa3b9f7ea
commit 3df0545a8b
2 changed files with 53 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
src/pkg/go/scanner/scanner.go
View File

@ -572,14 +572,25 @@ scanAgain:
// determine token value
insertSemi := false
switch ch := s.ch; {
case isLetter(ch):
case 'a' <= ch && ch <= 'z':
// literals start with a lower-case letter
lit = s.scanIdentifier()
tok = token.Lookup(lit)
switch tok {
case token.IDENT, token.BREAK, token.CONTINUE, token.FALLTHROUGH, token.RETURN:
if len(lit) > 1 {
// keywords are longer than one letter - avoid lookup otherwise
tok = token.Lookup(lit)
switch tok {
case token.IDENT, token.BREAK, token.CONTINUE, token.FALLTHROUGH, token.RETURN:
insertSemi = true
}
} else {
insertSemi = true
tok = token.IDENT
}
case digitVal(ch) < 10:
case 'A' <= ch && ch <= 'Z' || ch == '_':
insertSemi = true
tok = token.IDENT
lit = s.scanIdentifier()
case '0' <= ch && ch <= '9':
insertSemi = true
tok, lit = s.scanNumber(false)
default:
@ -612,7 +623,7 @@ scanAgain:
case ':':
tok = s.switch2(token.COLON, token.DEFINE)
case '.':
if digitVal(s.ch) < 10 {
if '0' <= s.ch && s.ch <= '9' {
insertSemi = true
tok, lit = s.scanNumber(true)
} else if s.ch == '.' {
@ -704,10 +715,17 @@ scanAgain:
case '|':
tok = s.switch3(token.OR, token.OR_ASSIGN, '|', token.LOR)
default:
s.error(s.file.Offset(pos), fmt.Sprintf("illegal character %#U", ch))
insertSemi = s.insertSemi // preserve insertSemi info
tok = token.ILLEGAL
lit = string(ch)
if isLetter(ch) {
// handle any letters we might have missed
insertSemi = true
tok = token.IDENT
s.scanIdentifier()
} else {
s.error(s.file.Offset(pos), fmt.Sprintf("illegal character %#U", ch))
insertSemi = s.insertSemi // preserve insertSemi info
tok = token.ILLEGAL
lit = string(ch)
}
}
}
if s.mode&dontInsertSemis == 0 {

26
src/pkg/go/scanner/scanner_test.go
View File

@ -6,6 +6,7 @@ package scanner
import (
"go/token"
"io/ioutil"
"os"
"path/filepath"
"runtime"
@ -705,7 +706,7 @@ func BenchmarkScan(b *testing.B) {
file := fset.AddFile("", fset.Base(), len(source))
var s Scanner
b.StartTimer()
for i := b.N - 1; i >= 0; i-- {
for i := 0; i < b.N; i++ {
s.Init(file, source, nil, ScanComments)
for {
_, tok, _ := s.Scan()
@ -715,3 +716,26 @@ func BenchmarkScan(b *testing.B) {
}
}
}
func BenchmarkScanFile(b *testing.B) {
b.StopTimer()
const filename = "scanner.go"
src, err := ioutil.ReadFile(filename)
if err != nil {
panic(err)
}
fset := token.NewFileSet()
file := fset.AddFile(filename, fset.Base(), len(src))
b.SetBytes(int64(len(src)))
var s Scanner
b.StartTimer()
for i := 0; i < b.N; i++ {
s.Init(file, src, nil, ScanComments)
for {
_, tok, _ := s.Scan()
if tok == token.EOF {
break
}
}
}
}