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authorRob Pike <r@golang.org>2014-10-17 09:00:07 -0700
committerRob Pike <r@golang.org>2014-10-17 09:00:07 -0700
commit6be8c76395e82d19791f492d38a46084cab8811c (patch)
tree64717ebf6e09303e47d2d3f0b23802915ddf50c6 /src/encoding
parent3ab342d4e6b60fee54d7ed929897beb95fe02a8c (diff)
downloadgo-6be8c76395e82d19791f492d38a46084cab8811c.tar.gz
encoding/gob: speed up encoding of arrays and slices
We borrow a trick from the fmt package and avoid reflection to walk the elements when possible. We could push further with unsafe (and we may) but this is a good start. Decode can benefit similarly; it will be done separately. Use go generate (engen.go) to produce the helper functions (enc_helpers.go). benchmark old ns/op new ns/op delta BenchmarkEndToEndPipe 6593 6482 -1.68% BenchmarkEndToEndByteBuffer 3662 3684 +0.60% BenchmarkEndToEndSliceByteBuffer 350306 351693 +0.40% BenchmarkComplex128Slice 96347 80045 -16.92% BenchmarkInt32Slice 42484 26008 -38.78% BenchmarkFloat64Slice 51143 36265 -29.09% BenchmarkStringSlice 53402 35077 -34.32% LGTM=rsc R=rsc CC=golang-codereviews https://codereview.appspot.com/156310043
Diffstat (limited to 'src/encoding')
-rw-r--r--src/encoding/gob/enc_helpers.go414
-rw-r--r--src/encoding/gob/encgen.go218
-rw-r--r--src/encoding/gob/encode.go15
-rw-r--r--src/encoding/gob/timing_test.go64
4 files changed, 708 insertions, 3 deletions
diff --git a/src/encoding/gob/enc_helpers.go b/src/encoding/gob/enc_helpers.go
new file mode 100644
index 000000000..1e6f30718
--- /dev/null
+++ b/src/encoding/gob/enc_helpers.go
@@ -0,0 +1,414 @@
+// Created by encgen --output enc_helpers.go; DO NOT EDIT
+
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+ "reflect"
+)
+
+var arrayHelper = map[reflect.Kind]encHelper{
+ reflect.Bool: encBoolArray,
+ reflect.Complex64: encComplex64Array,
+ reflect.Complex128: encComplex128Array,
+ reflect.Float32: encFloat32Array,
+ reflect.Float64: encFloat64Array,
+ reflect.Int: encIntArray,
+ reflect.Int16: encInt16Array,
+ reflect.Int32: encInt32Array,
+ reflect.Int64: encInt64Array,
+ reflect.Int8: encInt8Array,
+ reflect.String: encStringArray,
+ reflect.Uint: encUintArray,
+ reflect.Uint16: encUint16Array,
+ reflect.Uint32: encUint32Array,
+ reflect.Uint64: encUint64Array,
+ reflect.Uintptr: encUintptrArray,
+}
+
+var sliceHelper = map[reflect.Kind]encHelper{
+ reflect.Bool: encBoolSlice,
+ reflect.Complex64: encComplex64Slice,
+ reflect.Complex128: encComplex128Slice,
+ reflect.Float32: encFloat32Slice,
+ reflect.Float64: encFloat64Slice,
+ reflect.Int: encIntSlice,
+ reflect.Int16: encInt16Slice,
+ reflect.Int32: encInt32Slice,
+ reflect.Int64: encInt64Slice,
+ reflect.Int8: encInt8Slice,
+ reflect.String: encStringSlice,
+ reflect.Uint: encUintSlice,
+ reflect.Uint16: encUint16Slice,
+ reflect.Uint32: encUint32Slice,
+ reflect.Uint64: encUint64Slice,
+ reflect.Uintptr: encUintptrSlice,
+}
+
+func encBoolArray(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encBoolSlice(state, v.Slice(0, v.Len()))
+}
+
+func encBoolSlice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]bool)
+ if !ok {
+ // It is kind bool but not type bool. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != false || state.sendZero {
+ if x {
+ state.encodeUint(1)
+ } else {
+ state.encodeUint(0)
+ }
+ }
+ }
+ return true
+}
+
+func encComplex64Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encComplex64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encComplex64Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]complex64)
+ if !ok {
+ // It is kind complex64 but not type complex64. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0+0i || state.sendZero {
+ rpart := floatBits(float64(real(x)))
+ ipart := floatBits(float64(imag(x)))
+ state.encodeUint(rpart)
+ state.encodeUint(ipart)
+ }
+ }
+ return true
+}
+
+func encComplex128Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encComplex128Slice(state, v.Slice(0, v.Len()))
+}
+
+func encComplex128Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]complex128)
+ if !ok {
+ // It is kind complex128 but not type complex128. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0+0i || state.sendZero {
+ rpart := floatBits(real(x))
+ ipart := floatBits(imag(x))
+ state.encodeUint(rpart)
+ state.encodeUint(ipart)
+ }
+ }
+ return true
+}
+
+func encFloat32Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encFloat32Slice(state, v.Slice(0, v.Len()))
+}
+
+func encFloat32Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]float32)
+ if !ok {
+ // It is kind float32 but not type float32. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ bits := floatBits(float64(x))
+ state.encodeUint(bits)
+ }
+ }
+ return true
+}
+
+func encFloat64Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encFloat64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encFloat64Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]float64)
+ if !ok {
+ // It is kind float64 but not type float64. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ bits := floatBits(x)
+ state.encodeUint(bits)
+ }
+ }
+ return true
+}
+
+func encIntArray(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encIntSlice(state, v.Slice(0, v.Len()))
+}
+
+func encIntSlice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]int)
+ if !ok {
+ // It is kind int but not type int. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeInt(int64(x))
+ }
+ }
+ return true
+}
+
+func encInt16Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encInt16Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt16Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]int16)
+ if !ok {
+ // It is kind int16 but not type int16. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeInt(int64(x))
+ }
+ }
+ return true
+}
+
+func encInt32Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encInt32Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt32Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]int32)
+ if !ok {
+ // It is kind int32 but not type int32. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeInt(int64(x))
+ }
+ }
+ return true
+}
+
+func encInt64Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encInt64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt64Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]int64)
+ if !ok {
+ // It is kind int64 but not type int64. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeInt(x)
+ }
+ }
+ return true
+}
+
+func encInt8Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encInt8Slice(state, v.Slice(0, v.Len()))
+}
+
+func encInt8Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]int8)
+ if !ok {
+ // It is kind int8 but not type int8. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeInt(int64(x))
+ }
+ }
+ return true
+}
+
+func encStringArray(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encStringSlice(state, v.Slice(0, v.Len()))
+}
+
+func encStringSlice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]string)
+ if !ok {
+ // It is kind string but not type string. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != "" || state.sendZero {
+ state.encodeUint(uint64(len(x)))
+ state.b.WriteString(x)
+ }
+ }
+ return true
+}
+
+func encUintArray(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encUintSlice(state, v.Slice(0, v.Len()))
+}
+
+func encUintSlice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]uint)
+ if !ok {
+ // It is kind uint but not type uint. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeUint(uint64(x))
+ }
+ }
+ return true
+}
+
+func encUint16Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encUint16Slice(state, v.Slice(0, v.Len()))
+}
+
+func encUint16Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]uint16)
+ if !ok {
+ // It is kind uint16 but not type uint16. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeUint(uint64(x))
+ }
+ }
+ return true
+}
+
+func encUint32Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encUint32Slice(state, v.Slice(0, v.Len()))
+}
+
+func encUint32Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]uint32)
+ if !ok {
+ // It is kind uint32 but not type uint32. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeUint(uint64(x))
+ }
+ }
+ return true
+}
+
+func encUint64Array(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encUint64Slice(state, v.Slice(0, v.Len()))
+}
+
+func encUint64Slice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]uint64)
+ if !ok {
+ // It is kind uint64 but not type uint64. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeUint(x)
+ }
+ }
+ return true
+}
+
+func encUintptrArray(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return encUintptrSlice(state, v.Slice(0, v.Len()))
+}
+
+func encUintptrSlice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]uintptr)
+ if !ok {
+ // It is kind uintptr but not type uintptr. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != 0 || state.sendZero {
+ state.encodeUint(uint64(x))
+ }
+ }
+ return true
+}
diff --git a/src/encoding/gob/encgen.go b/src/encoding/gob/encgen.go
new file mode 100644
index 000000000..fa500e3da
--- /dev/null
+++ b/src/encoding/gob/encgen.go
@@ -0,0 +1,218 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build ignore
+
+// encgen writes the helper functions for encoding. Intended to be
+// used with go generate; see the invocation in encode.go.
+
+// TODO: We could do more by being unsafe. Add a -unsafe flag?
+
+package main
+
+import (
+ "bytes"
+ "flag"
+ "fmt"
+ "go/format"
+ "log"
+ "os"
+)
+
+var output = flag.String("output", "enc_helpers.go", "file name to write")
+
+type Type struct {
+ lower string
+ upper string
+ zero string
+ encoder string
+}
+
+var types = []Type{
+ {
+ "bool",
+ "Bool",
+ "false",
+ `if x {
+ state.encodeUint(1)
+ } else {
+ state.encodeUint(0)
+ }`,
+ },
+ {
+ "complex64",
+ "Complex64",
+ "0+0i",
+ `rpart := floatBits(float64(real(x)))
+ ipart := floatBits(float64(imag(x)))
+ state.encodeUint(rpart)
+ state.encodeUint(ipart)`,
+ },
+ {
+ "complex128",
+ "Complex128",
+ "0+0i",
+ `rpart := floatBits(real(x))
+ ipart := floatBits(imag(x))
+ state.encodeUint(rpart)
+ state.encodeUint(ipart)`,
+ },
+ {
+ "float32",
+ "Float32",
+ "0",
+ `bits := floatBits(float64(x))
+ state.encodeUint(bits)`,
+ },
+ {
+ "float64",
+ "Float64",
+ "0",
+ `bits := floatBits(x)
+ state.encodeUint(bits)`,
+ },
+ {
+ "int",
+ "Int",
+ "0",
+ `state.encodeInt(int64(x))`,
+ },
+ {
+ "int16",
+ "Int16",
+ "0",
+ `state.encodeInt(int64(x))`,
+ },
+ {
+ "int32",
+ "Int32",
+ "0",
+ `state.encodeInt(int64(x))`,
+ },
+ {
+ "int64",
+ "Int64",
+ "0",
+ `state.encodeInt(x)`,
+ },
+ {
+ "int8",
+ "Int8",
+ "0",
+ `state.encodeInt(int64(x))`,
+ },
+ {
+ "string",
+ "String",
+ `""`,
+ `state.encodeUint(uint64(len(x)))
+ state.b.WriteString(x)`,
+ },
+ {
+ "uint",
+ "Uint",
+ "0",
+ `state.encodeUint(uint64(x))`,
+ },
+ {
+ "uint16",
+ "Uint16",
+ "0",
+ `state.encodeUint(uint64(x))`,
+ },
+ {
+ "uint32",
+ "Uint32",
+ "0",
+ `state.encodeUint(uint64(x))`,
+ },
+ {
+ "uint64",
+ "Uint64",
+ "0",
+ `state.encodeUint(x)`,
+ },
+ {
+ "uintptr",
+ "Uintptr",
+ "0",
+ `state.encodeUint(uint64(x))`,
+ },
+ // uint8 Handled separately.
+}
+
+func main() {
+ log.SetFlags(0)
+ log.SetPrefix("helpergen: ")
+ flag.Parse()
+ if flag.NArg() != 0 {
+ log.Fatal("usage: encgen [--output filename]")
+ }
+ var b bytes.Buffer
+ fmt.Fprintf(&b, "// Created by encgen --output %s; DO NOT EDIT\n", *output)
+ fmt.Fprint(&b, header)
+ printMaps(&b, "array", "Array")
+ fmt.Fprint(&b, "\n")
+ printMaps(&b, "slice", "Slice")
+ for _, t := range types {
+ fmt.Fprintf(&b, arrayHelper, t.lower, t.upper)
+ fmt.Fprintf(&b, sliceHelper, t.lower, t.upper, t.zero, t.encoder)
+ }
+ source, err := format.Source(b.Bytes())
+ if err != nil {
+ log.Fatal("source format error:", err)
+ }
+ fd, err := os.Create(*output)
+ _, err = fd.Write(source)
+ if err != nil {
+ log.Fatal(err)
+ }
+}
+
+func printMaps(b *bytes.Buffer, lowerClass, upperClass string) {
+ fmt.Fprintf(b, "var %sHelper = map[reflect.Kind]encHelper{\n", lowerClass)
+ for _, t := range types {
+ fmt.Fprintf(b, "reflect.%s: enc%s%s,\n", t.upper, t.upper, upperClass)
+ }
+ fmt.Fprintf(b, "}\n")
+}
+
+const header = `
+// Copyright 2014 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package gob
+
+import (
+ "reflect"
+)
+
+`
+
+const arrayHelper = `
+func enc%[2]sArray(state *encoderState, v reflect.Value) bool {
+ // Can only slice if it is addressable.
+ if !v.CanAddr() {
+ return false
+ }
+ return enc%[2]sSlice(state, v.Slice(0, v.Len()))
+}
+`
+
+const sliceHelper = `
+func enc%[2]sSlice(state *encoderState, v reflect.Value) bool {
+ slice, ok := v.Interface().([]%[1]s)
+ if !ok {
+ // It is kind %[1]s but not type %[1]s. TODO: We can handle this unsafely.
+ return false
+ }
+ for _, x := range slice {
+ if x != %[3]s || state.sendZero {
+ %[4]s
+ }
+ }
+ return true
+}
+`
diff --git a/src/encoding/gob/encode.go b/src/encoding/gob/encode.go
index 04a85410c..3b8d0b427 100644
--- a/src/encoding/gob/encode.go
+++ b/src/encoding/gob/encode.go
@@ -2,6 +2,8 @@
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
+//go:generate go run encgen.go -output enc_helpers.go
+
package gob
import (
@@ -13,6 +15,8 @@ import (
const uint64Size = 8
+type encHelper func(state *encoderState, v reflect.Value) bool
+
// encoderState is the global execution state of an instance of the encoder.
// Field numbers are delta encoded and always increase. The field
// number is initialized to -1 so 0 comes out as delta(1). A delta of
@@ -291,12 +295,15 @@ func (enc *Encoder) encodeStruct(b *bytes.Buffer, engine *encEngine, value refle
}
// encodeArray encodes an array.
-func (enc *Encoder) encodeArray(b *bytes.Buffer, value reflect.Value, op encOp, elemIndir int, length int) {
+func (enc *Encoder) encodeArray(b *bytes.Buffer, value reflect.Value, op encOp, elemIndir int, length int, helper encHelper) {
state := enc.newEncoderState(b)
defer enc.freeEncoderState(state)
state.fieldnum = -1
state.sendZero = true
state.encodeUint(uint64(length))
+ if helper != nil && helper(state, value) {
+ return
+ }
for i := 0; i < length; i++ {
elem := value.Index(i)
if elemIndir > 0 {
@@ -501,19 +508,21 @@ func encOpFor(rt reflect.Type, inProgress map[reflect.Type]*encOp, building map[
}
// Slices have a header; we decode it to find the underlying array.
elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+ helper := sliceHelper[t.Elem().Kind()]
op = func(i *encInstr, state *encoderState, slice reflect.Value) {
if !state.sendZero && slice.Len() == 0 {
return
}
state.update(i)
- state.enc.encodeArray(state.b, slice, *elemOp, elemIndir, slice.Len())
+ state.enc.encodeArray(state.b, slice, *elemOp, elemIndir, slice.Len(), helper)
}
case reflect.Array:
// True arrays have size in the type.
elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+ helper := arrayHelper[t.Elem().Kind()]
op = func(i *encInstr, state *encoderState, array reflect.Value) {
state.update(i)
- state.enc.encodeArray(state.b, array, *elemOp, elemIndir, array.Len())
+ state.enc.encodeArray(state.b, array, *elemOp, elemIndir, array.Len(), helper)
}
case reflect.Map:
keyOp, keyIndir := encOpFor(t.Key(), inProgress, building)
diff --git a/src/encoding/gob/timing_test.go b/src/encoding/gob/timing_test.go
index ec55c4d63..abfe936e8 100644
--- a/src/encoding/gob/timing_test.go
+++ b/src/encoding/gob/timing_test.go
@@ -131,3 +131,67 @@ func TestCountDecodeMallocs(t *testing.T) {
t.Fatalf("mallocs per decode of type Bench: %v; wanted 4\n", allocs)
}
}
+
+func BenchmarkComplex128Slice(b *testing.B) {
+ var buf bytes.Buffer
+ enc := NewEncoder(&buf)
+ a := make([]complex128, 1000)
+ for i := range a {
+ a[i] = 1.2 + 3.4i
+ }
+ for i := 0; i < b.N; i++ {
+ buf.Reset()
+ err := enc.Encode(a)
+ if err != nil {
+ b.Fatal(err)
+ }
+ }
+}
+
+func BenchmarkInt32Slice(b *testing.B) {
+ var buf bytes.Buffer
+ enc := NewEncoder(&buf)
+ a := make([]int32, 1000)
+ for i := range a {
+ a[i] = 1234
+ }
+ for i := 0; i < b.N; i++ {
+ buf.Reset()
+ err := enc.Encode(a)
+ if err != nil {
+ b.Fatal(err)
+ }
+ }
+}
+
+func BenchmarkFloat64Slice(b *testing.B) {
+ var buf bytes.Buffer
+ enc := NewEncoder(&buf)
+ a := make([]float64, 1000)
+ for i := range a {
+ a[i] = 1.23e4
+ }
+ for i := 0; i < b.N; i++ {
+ buf.Reset()
+ err := enc.Encode(a)
+ if err != nil {
+ b.Fatal(err)
+ }
+ }
+}
+
+func BenchmarkStringSlice(b *testing.B) {
+ var buf bytes.Buffer
+ enc := NewEncoder(&buf)
+ a := make([]string, 1000)
+ for i := range a {
+ a[i] = "now is the time"
+ }
+ for i := 0; i < b.N; i++ {
+ buf.Reset()
+ err := enc.Encode(a)
+ if err != nil {
+ b.Fatal(err)
+ }
+ }
+}