encoding/json: add marshal/unmarshal benchmark

R=bradfitz
CC=golang-dev
https://golang.org/cl/5387041

src/pkg/encoding/json/bench_test.go

+// Copyright 2011 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.
+
+// Large data benchmark.
+// The JSON data is a summary of agl's changes in the
+// go, webkit, and chromium open source projects.
+// We benchmark converting between the JSON form
+// and in-memory data structures.
+
+package json
+
+import (
+	"bytes"
+	"compress/gzip"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+type codeResponse struct {
+	Tree     *codeNode `json:"tree"`
+	Username string    `json:"username"`
+}
+
+type codeNode struct {
+	Name     string      `json:"name"`
+	Kids     []*codeNode `json:"kids"`
+	CLWeight float64     `json:"cl_weight"`
+	Touches  int         `json:"touches"`
+	MinT     int64       `json:"min_t"`
+	MaxT     int64       `json:"max_t"`
+	MeanT    int64       `json:"mean_t"`
+}
+
+var codeJSON []byte
+var codeStruct codeResponse
+
+func codeInit() {
+	f, err := os.Open("testdata/code.json.gz")
+	if err != nil {
+		panic(err)
+	}
+	defer f.Close()
+	gz, err := gzip.NewReader(f)
+	if err != nil {
+		panic(err)
+	}
+	data, err := ioutil.ReadAll(gz)
+	if err != nil {
+		panic(err)
+	}
+
+	codeJSON = data
+
+	if err := Unmarshal(codeJSON, &codeStruct); err != nil {
+		panic("unmarshal code.json: " + err.Error())
+	}
+
+	if data, err = Marshal(&codeStruct); err != nil {
+		panic("marshal code.json: " + err.Error())
+	}
+
+	if !bytes.Equal(data, codeJSON) {
+		println("different lengths", len(data), len(codeJSON))
+		for i := 0; i < len(data) && i < len(codeJSON); i++ {
+			if data[i] != codeJSON[i] {
+				println("re-marshal: changed at byte", i)
+				println("orig: ", string(codeJSON[i-10:i+10]))
+				println("new: ", string(data[i-10:i+10]))
+				break
+			}
+		}
+		panic("re-marshal code.json: different result")
+	}
+}
+
+func BenchmarkCodeEncoder(b *testing.B) {
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	enc := NewEncoder(ioutil.Discard)
+	for i := 0; i < b.N; i++ {
+		if err := enc.Encode(&codeStruct); err != nil {
+			panic(err)
+		}
+	}
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeMarshal(b *testing.B) {
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	for i := 0; i < b.N; i++ {
+		if _, err := Marshal(&codeStruct); err != nil {
+			panic(err)
+		}
+	}
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeDecoder(b *testing.B) {
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	var buf bytes.Buffer
+	dec := NewDecoder(&buf)
+	var r codeResponse
+	for i := 0; i < b.N; i++ {
+		buf.Write(codeJSON)
+		// hide EOF
+		buf.WriteByte('\n')
+		buf.WriteByte('\n')
+		buf.WriteByte('\n')
+		if err := dec.Decode(&r); err != nil {
+			panic(err)
+		}
+	}
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeUnmarshal(b *testing.B) {
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	for i := 0; i < b.N; i++ {
+		var r codeResponse
+		if err := Unmarshal(codeJSON, &r); err != nil {
+			panic(err)
+		}
+	}
+	b.SetBytes(int64(len(codeJSON)))
+}
+
+func BenchmarkCodeUnmarshalReuse(b *testing.B) {
+	if codeJSON == nil {
+		b.StopTimer()
+		codeInit()
+		b.StartTimer()
+	}
+	var r codeResponse
+	for i := 0; i < b.N; i++ {
+		if err := Unmarshal(codeJSON, &r); err != nil {
+			panic(err)
+		}
+	}
+	b.SetBytes(int64(len(codeJSON)))
+}