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undo CL 101330053 / c19c9a063fe8

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sync.Pool is not supposed to be used everywhere, but is
a last resort.

««« original CL description
strings: use sync.Pool to cache buffer

benchmark                         old ns/op    new ns/op    delta
BenchmarkByteReplacerWriteString       3596         3094  -13.96%

benchmark                        old allocs   new allocs    delta
BenchmarkByteReplacerWriteString          1            0  -100.00%

LGTM=dvyukov
R=bradfitz, dave, dvyukov
CC=golang-codereviews
https://golang.org/cl/101330053
»»»

LGTM=dave
R=r, dave
CC=golang-codereviews
https://golang.org/cl/102610043
This commit is contained in:
Rui Ueyama 2014-06-22 15:26:30 -07:00
parent 5b342f7804
commit a200e0b8fd
2 changed files with 25 additions and 50 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/pkg/strings/replace.go
View File

@ -4,10 +4,7 @@
package strings
import (
"io"
"sync"
)
import "io"
// A Replacer replaces a list of strings with replacements.
type Replacer struct {
@ -454,31 +451,27 @@ func (r *byteReplacer) Replace(s string) string {
return string(buf)
}
var bufferPool = sync.Pool{
New: func() interface{} {
b := make([]byte, 4096)
return &b
},
}
func (r *byteReplacer) WriteString(w io.Writer, s string) (n int, err error) {
bp := bufferPool.Get().(*[]byte)
buf := *bp
// TODO(bradfitz): use io.WriteString with slices of s, avoiding allocation.
bufsize := 32 << 10
if len(s) < bufsize {
bufsize = len(s)
}
buf := make([]byte, bufsize)
for len(s) > 0 {
ncopy := copy(buf, s)
ncopy := copy(buf, s[:])
s = s[ncopy:]
for i, b := range buf[:ncopy] {
buf[i] = r.new[b]
}
s = s[ncopy:]
var wn int
wn, err = w.Write(buf[:ncopy])
wn, err := w.Write(buf[:ncopy])
n += wn
if err != nil {
break
return n, err
}
}
bufferPool.Put(bp)
return
return n, nil
}
// byteStringReplacer is the implementation that's used when all the

42
src/pkg/strings/replace_test.go
View File

@ -308,21 +308,20 @@ func TestReplacer(t *testing.T) {
}
}
var algorithmTestCases = []struct {
r *Replacer
want string
}{
{capitalLetters, "*strings.byteReplacer"},
{htmlEscaper, "*strings.byteStringReplacer"},
{NewReplacer("12", "123"), "*strings.singleStringReplacer"},
{NewReplacer("1", "12"), "*strings.byteStringReplacer"},
{NewReplacer("", "X"), "*strings.genericReplacer"},
{NewReplacer("a", "1", "b", "12", "cde", "123"), "*strings.genericReplacer"},
}
// TestPickAlgorithm tests that NewReplacer picks the correct algorithm.
func TestPickAlgorithm(t *testing.T) {
for i, tc := range algorithmTestCases {
testCases := []struct {
r *Replacer
want string
}{
{capitalLetters, "*strings.byteReplacer"},
{htmlEscaper, "*strings.byteStringReplacer"},
{NewReplacer("12", "123"), "*strings.singleStringReplacer"},
{NewReplacer("1", "12"), "*strings.byteStringReplacer"},
{NewReplacer("", "X"), "*strings.genericReplacer"},
{NewReplacer("a", "1", "b", "12", "cde", "123"), "*strings.genericReplacer"},
}
for i, tc := range testCases {
got := fmt.Sprintf("%T", tc.r.Replacer())
if got != tc.want {
t.Errorf("%d. algorithm = %s, want %s", i, got, tc.want)
@ -330,23 +329,6 @@ func TestPickAlgorithm(t *testing.T) {
}
}
type errWriter struct{}
func (errWriter) Write(p []byte) (n int, err error) {
return 0, fmt.Errorf("unwritable")
}
// TestWriteStringError tests that WriteString returns an error
// received from the underlying io.Writer.
func TestWriteStringError(t *testing.T) {
for i, tc := range algorithmTestCases {
n, err := tc.r.WriteString(errWriter{}, "abc")
if n != 0 || err == nil || err.Error() != "unwritable" {
t.Errorf("%d. WriteStringError = %d, %v, want 0, unwritable", i, n, err)
}
}
}
// TestGenericTrieBuilding verifies the structure of the generated trie. There
// is one node per line, and the key ending with the current line is in the
// trie if it ends with a "+".