Add a json parser

.gitignore

@@ -1,2 +1,5 @@
 .idea
 *.iml
+*.exe
+cpu.out
+mem.out

json/json.go

@@ -0,0 +1,68 @@
+package json
+
+import (
+	"errors"
+
+	. "github.com/vektah/goparsify"
+)
+
+var (
+	value Parser
+
+	array = Map(And(WS, "[", Kleene(&value, And(WS, ",")), "]"), func(n Node) Node {
+		return n.([]Node)[1].([]Node)
+	})
+	properties = Kleene(And(WS, String('"'), WS, ":", WS, &value), ",")
+	object     = Map(And(WS, "{", WS, properties, WS, "}"), func(n Node) Node {
+		ret := map[string]interface{}{}
+
+		for _, prop := range n.([]Node)[1].([]Node) {
+			vals := prop.([]Node)
+			if len(vals) == 3 {
+				ret[vals[0].(string)] = vals[2]
+			} else {
+				ret[vals[0].(string)] = nil
+			}
+		}
+
+		return ret
+	})
+
+	_null = Map(And(WS, "null"), func(n Node) Node {
+		return nil
+	})
+
+	_true = Map(And(WS, "true"), func(n Node) Node {
+		return true
+	})
+
+	_false = Map(And(WS, "false"), func(n Node) Node {
+		return false
+	})
+
+	Y = Map(And(&value, WS), func(n Node) Node {
+		nodes := n.([]Node)
+		if len(nodes) > 0 {
+			return nodes[0]
+		}
+		return nil
+	})
+)
+
+func init() {
+	value = Any(_null, _true, _false, String('"'), array, object)
+}
+
+func Unmarshal(input string) (interface{}, error) {
+	result, remaining, err := ParseString(Y, input)
+
+	if err != nil {
+		return result, err
+	}
+
+	if remaining != "" {
+		return result, errors.New("left unparsed: " + remaining)
+	}
+
+	return result, err
+}

json/json_test.go

@@ -0,0 +1,70 @@
+package json
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+	. "github.com/vektah/goparsify"
+)
+
+func TestUnmarshal(t *testing.T) {
+	t.Run("basic types", func(t *testing.T) {
+		result, err := Unmarshal(`true`)
+		require.NoError(t, err)
+		require.Equal(t, true, result)
+
+		result, err = Unmarshal(`false`)
+		require.NoError(t, err)
+		require.Equal(t, false, result)
+
+		result, err = Unmarshal(`null`)
+		require.NoError(t, err)
+		require.Equal(t, nil, result)
+
+		result, err = Unmarshal(`"true"`)
+		require.NoError(t, err)
+		require.Equal(t, "true", result)
+	})
+
+	t.Run("array", func(t *testing.T) {
+		result, err := Unmarshal(`[true, null, false]`)
+		require.NoError(t, err)
+		require.Equal(t, []Node{true, nil, false}, result)
+	})
+
+	t.Run("object", func(t *testing.T) {
+		result, err := Unmarshal(`{"true":true, "false":false, "null": null} `)
+		require.NoError(t, err)
+		require.Equal(t, map[string]interface{}{"true": true, "false": false, "null": nil}, result)
+	})
+}
+
+const benchmarkString = `{"true":true, "false":false, "null": null}`
+
+//func BenchmarkUnmarshalParsec(b *testing.B) {
+//	bytes := []byte(benchmarkString)
+//
+//	for i := 0; i < b.N; i++ {
+//		scanner := parsecJson.NewJSONScanner(bytes)
+//		_, remaining := parsecJson.Y(scanner)
+//
+//		require.True(b, remaining.Endof())
+//	}
+//}
+
+func BenchmarkUnmarshalParsify(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		_, err := Unmarshal(benchmarkString)
+		require.NoError(b, err)
+	}
+}
+
+//
+//func BenchmarkUnmarshalStdlib(b *testing.B) {
+//	bytes := []byte(benchmarkString)
+//	var result interface{}
+//	for i := 0; i < b.N; i++ {
+//		err := stdlibJson.Unmarshal(bytes, &result)
+//		require.NoError(b, err)
+//	}
+//}

json/profile/cpuprofile.bat

@@ -0,0 +1,3 @@
+go build
+profile.exe -cpuprofile cpu.out
+go tool pprof --inuse_objects profile.exe cpu.out

json/profile/json.go

@@ -0,0 +1,55 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+	"runtime"
+	"runtime/pprof"
+
+	"github.com/vektah/goparsify/json"
+)
+
+var cpuprofile = flag.String("cpuprofile", "", "write cpu profile to file")
+var memprofile = flag.String("memprofile", "", "write memory profile to this file")
+
+func main() {
+	flag.Parse()
+	if *cpuprofile != "" {
+		f, err := os.Create(*cpuprofile)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		pprof.StartCPUProfile(f)
+
+		defer func() {
+			pprof.StopCPUProfile()
+			err := f.Close()
+			if err != nil {
+				panic(err)
+			}
+		}()
+	}
+	if *memprofile != "" {
+		runtime.MemProfileRate = 1
+	}
+
+	for i := 0; i < 10000; i++ {
+		_, err := json.Unmarshal(`{"true":true, "false":false, "null": null}`)
+		if err != nil {
+			panic(err)
+		}
+	}
+
+	if *memprofile != "" {
+		f, err := os.Create(*memprofile)
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		pprof.WriteHeapProfile(f)
+		f.Close()
+		return
+	}
+}

json/profile/memprofile.bat

@@ -0,0 +1,3 @@
+go build
+profile.exe -memprofile mem.out
+go tool pprof --inuse_objects profile.exe mem.out