encoding/json: avoid some more pointer receivers

A few encoder struct types, such as map and slice, only encapsulate
other prepared encoder funcs. Using pointer receivers has no advantage,
and makes calling these methods slightly more expensive.

Not a huge performance win, but certainly an easy one. The struct types
used in the benchmark below contain one slice field and one pointer
field.

name           old time/op    new time/op    delta
CodeEncoder-4    5.48ms ± 0%    5.39ms ± 0%  -1.66%  (p=0.010 n=6+4)

name           old speed      new speed      delta
CodeEncoder-4   354MB/s ± 0%   360MB/s ± 0%  +1.69%  (p=0.010 n=6+4)

Updates #5683.

Change-Id: I9f78dbe07fcc6fbf19a6d96c22f5d6970db9eca4
Reviewed-on: https://go-review.googlesource.com/131400
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

diff --git a/src/encoding/json/encode.go b/src/encoding/json/encode.go
index f475d5688ab51c03deb594c5270b29d1527e8869..ec49ceb93ee00deb64883cd0c815db9d2c1db51d 100644 (file)
--- a/src/encoding/json/encode.go
+++ b/src/encoding/json/encode.go
@@ -674,7 +674,7 @@ type mapEncoder struct {
        elemEnc encoderFunc
 }
 
-func (me *mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
        if v.IsNil() {
                e.WriteString("null")
                return
@@ -713,7 +713,7 @@ func newMapEncoder(t reflect.Type) encoderFunc {
                        return unsupportedTypeEncoder
                }
        }
-       me := &mapEncoder{typeEncoder(t.Elem())}
+       me := mapEncoder{typeEncoder(t.Elem())}
        return me.encode
 }
 
@@ -752,7 +752,7 @@ type sliceEncoder struct {
        arrayEnc encoderFunc
 }
 
-func (se *sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+func (se sliceEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
        if v.IsNil() {
                e.WriteString("null")
                return
@@ -768,7 +768,7 @@ func newSliceEncoder(t reflect.Type) encoderFunc {
                        return encodeByteSlice
                }
        }
-       enc := &sliceEncoder{newArrayEncoder(t)}
+       enc := sliceEncoder{newArrayEncoder(t)}
        return enc.encode
 }
 
@@ -776,7 +776,7 @@ type arrayEncoder struct {
        elemEnc encoderFunc
 }
 
-func (ae *arrayEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+func (ae arrayEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
        e.WriteByte('[')
        n := v.Len()
        for i := 0; i < n; i++ {
@@ -789,7 +789,7 @@ func (ae *arrayEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 }
 
 func newArrayEncoder(t reflect.Type) encoderFunc {
-       enc := &arrayEncoder{typeEncoder(t.Elem())}
+       enc := arrayEncoder{typeEncoder(t.Elem())}
        return enc.encode
 }
 
@@ -797,7 +797,7 @@ type ptrEncoder struct {
        elemEnc encoderFunc
 }
 
-func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+func (pe ptrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
        if v.IsNil() {
                e.WriteString("null")
                return
@@ -806,7 +806,7 @@ func (pe *ptrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
 }
 
 func newPtrEncoder(t reflect.Type) encoderFunc {
-       enc := &ptrEncoder{typeEncoder(t.Elem())}
+       enc := ptrEncoder{typeEncoder(t.Elem())}
        return enc.encode
 }
 
@@ -814,7 +814,7 @@ type condAddrEncoder struct {
        canAddrEnc, elseEnc encoderFunc
 }
 
-func (ce *condAddrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
+func (ce condAddrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
        if v.CanAddr() {
                ce.canAddrEnc(e, v, opts)
        } else {
@@ -825,7 +825,7 @@ func (ce *condAddrEncoder) encode(e *encodeState, v reflect.Value, opts encOpts)
 // newCondAddrEncoder returns an encoder that checks whether its value
 // CanAddr and delegates to canAddrEnc if so, else to elseEnc.
 func newCondAddrEncoder(canAddrEnc, elseEnc encoderFunc) encoderFunc {
-       enc := &condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
+       enc := condAddrEncoder{canAddrEnc: canAddrEnc, elseEnc: elseEnc}
        return enc.encode
 }