fmt: use sync.Pool

Update #4720

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/43990043

diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index 1ea816d6d5f26c37a2c360e40845f298d497ed6e..2f13bcd95e971415401e75a10b0f7d36d209d930 100644 (file)
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -124,45 +124,13 @@ type pp struct {
        fmt        fmt
 }
 
-// A cache holds a set of reusable objects.
-// The slice is a stack (LIFO).
-// If more are needed, the cache creates them by calling new.
-type cache struct {
-       mu    sync.Mutex
-       saved []interface{}
-       new   func() interface{}
+var ppFree = sync.Pool{
+       New: func() interface{} { return new(pp) },
 }
 
-func (c *cache) put(x interface{}) {
-       c.mu.Lock()
-       if len(c.saved) < cap(c.saved) {
-               c.saved = append(c.saved, x)
-       }
-       c.mu.Unlock()
-}
-
-func (c *cache) get() interface{} {
-       c.mu.Lock()
-       n := len(c.saved)
-       if n == 0 {
-               c.mu.Unlock()
-               return c.new()
-       }
-       x := c.saved[n-1]
-       c.saved = c.saved[0 : n-1]
-       c.mu.Unlock()
-       return x
-}
-
-func newCache(f func() interface{}) *cache {
-       return &cache{saved: make([]interface{}, 0, 100), new: f}
-}
-
-var ppFree = newCache(func() interface{} { return new(pp) })
-
 // newPrinter allocates a new pp struct or grab a cached one.
 func newPrinter() *pp {
-       p := ppFree.get().(*pp)
+       p := ppFree.Get().(*pp)
        p.panicking = false
        p.erroring = false
        p.fmt.init(&p.buf)
@@ -178,7 +146,7 @@ func (p *pp) free() {
        p.buf = p.buf[:0]
        p.arg = nil
        p.value = reflect.Value{}
-       ppFree.put(p)
+       ppFree.Put(p)
 }
 
 func (p *pp) Width() (wid int, ok bool) { return p.fmt.wid, p.fmt.widPresent }

diff --git a/src/pkg/fmt/scan.go b/src/pkg/fmt/scan.go
index 5b1be5891b8fd9b47cec2247f76dda4f62b89be7..c73b8b60283e4e9940096a7ffa2389966c1f76cf 100644 (file)
--- a/src/pkg/fmt/scan.go
+++ b/src/pkg/fmt/scan.go
@@ -11,6 +11,7 @@ import (
        "os"
        "reflect"
        "strconv"
+       "sync"
        "unicode/utf8"
 )
 
@@ -380,7 +381,9 @@ func (r *readRune) ReadRune() (rr rune, size int, err error) {
        return
 }
 
-var ssFree = newCache(func() interface{} { return new(ss) })
+var ssFree = sync.Pool{
+       New: func() interface{} { return new(ss) },
+}
 
 // newScanState allocates a new ss struct or grab a cached one.
 func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
@@ -395,7 +398,7 @@ func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
                return
        }
 
-       s = ssFree.get().(*ss)
+       s = ssFree.Get().(*ss)
        if rr, ok := r.(io.RuneReader); ok {
                s.rr = rr
        } else {
@@ -427,7 +430,7 @@ func (s *ss) free(old ssave) {
        }
        s.buf = s.buf[:0]
        s.rr = nil
-       ssFree.put(s)
+       ssFree.Put(s)
 }
 
 // skipSpace skips spaces and maybe newlines.