Merge pull request #257 from fjl/rlp-encoder

rlp: add functions for encoding

rlp/decode.go

@@ -329,16 +329,10 @@ type field struct {
 }
 
 func makeStructDecoder(typ reflect.Type) (decoder, error) {
-	var fields []field
-	for i := 0; i < typ.NumField(); i++ {
-		if f := typ.Field(i); f.PkgPath == "" { // exported
-			info, err := cachedTypeInfo1(f.Type)
+	fields, err := structFields(typ)
 	if err != nil {
 		return nil, err
 	}
-			fields = append(fields, field{i, info})
-		}
-	}
 	dec := func(s *Stream, val reflect.Value) (err error) {
 		if _, err = s.List(); err != nil {
 			return wrapStreamError(err, typ)

rlp/decode_test.go

@@ -8,8 +8,6 @@ import (
 	"math/big"
 	"reflect"
 	"testing"
-
-	"github.com/ethereum/go-ethereum/ethutil"
 )
 
 func TestStreamKind(t *testing.T) {
@@ -509,13 +507,13 @@ func ExampleStream() {
 }
 
 func BenchmarkDecode(b *testing.B) {
-	enc := encTest(90000)
+	enc := encodeTestSlice(90000)
 	b.SetBytes(int64(len(enc)))
 	b.ReportAllocs()
 	b.ResetTimer()
 
 	for i := 0; i < b.N; i++ {
-		var s []int
+		var s []uint
 		r := bytes.NewReader(enc)
 		if err := Decode(r, &s); err != nil {
 			b.Fatalf("Decode error: %v", err)
@@ -524,12 +522,12 @@ func BenchmarkDecode(b *testing.B) {
 }
 
 func BenchmarkDecodeIntSliceReuse(b *testing.B) {
-	enc := encTest(100000)
+	enc := encodeTestSlice(100000)
 	b.SetBytes(int64(len(enc)))
 	b.ReportAllocs()
 	b.ResetTimer()
 
-	var s []int
+	var s []uint
 	for i := 0; i < b.N; i++ {
 		r := bytes.NewReader(enc)
 		if err := Decode(r, &s); err != nil {
@@ -538,12 +536,16 @@ func BenchmarkDecodeIntSliceReuse(b *testing.B) {
 	}
 }
 
-func encTest(n int) []byte {
-	s := make([]interface{}, n)
-	for i := 0; i < n; i++ {
+func encodeTestSlice(n uint) []byte {
+	s := make([]uint, n)
+	for i := uint(0); i < n; i++ {
 		s[i] = i
 	}
-	return ethutil.Encode(s)
+	b, err := EncodeToBytes(s)
+	if err != nil {
+		panic(fmt.Sprintf("encode error: %v", err))
+	}
+	return b
 }
 
 func unhex(str string) []byte {

rlp/encoder_example_test.go

+package rlp
+
+import (
+	"fmt"
+	"io"
+)
+
+type MyCoolType struct {
+	Name string
+	a, b uint
+}
+
+// EncodeRLP writes x as RLP list [a, b] that omits the Name field.
+func (x *MyCoolType) EncodeRLP(w io.Writer) (err error) {
+	// Note: the receiver can be a nil pointer. This allows you to
+	// control the encoding of nil, but it also means that you have to
+	// check for a nil receiver.
+	if x == nil {
+		err = Encode(w, []uint{0, 0})
+	} else {
+		err = Encode(w, []uint{x.a, x.b})
+	}
+	return err
+}
+
+func ExampleEncoder() {
+	var t *MyCoolType // t is nil pointer to MyCoolType
+	bytes, _ := EncodeToBytes(t)
+	fmt.Printf("%v → %X\n", t, bytes)
+
+	t = &MyCoolType{Name: "foobar", a: 5, b: 6}
+	bytes, _ = EncodeToBytes(t)
+	fmt.Printf("%v → %X\n", t, bytes)
+
+	// Output:
+	// <nil> → C28080
+	// &{foobar 5 6} → C20506
+}

rlp/typecache.go

@@ -5,16 +5,19 @@ import (
 	"sync"
 )
 
-type decoder func(*Stream, reflect.Value) error
+var (
+	typeCacheMutex sync.RWMutex
+	typeCache      = make(map[reflect.Type]*typeinfo)
+)
 
 type typeinfo struct {
 	decoder
+	writer
 }
 
-var (
-	typeCacheMutex sync.RWMutex
-	typeCache      = make(map[reflect.Type]*typeinfo)
-)
+type decoder func(*Stream, reflect.Value) error
+
+type writer func(reflect.Value, *encbuf) error
 
 func cachedTypeInfo(typ reflect.Type) (*typeinfo, error) {
 	typeCacheMutex.RLock()
@@ -49,11 +52,27 @@ func cachedTypeInfo1(typ reflect.Type) (*typeinfo, error) {
 	return typeCache[typ], err
 }
 
+func structFields(typ reflect.Type) (fields []field, err error) {
+	for i := 0; i < typ.NumField(); i++ {
+		if f := typ.Field(i); f.PkgPath == "" { // exported
+			info, err := cachedTypeInfo1(f.Type)
+			if err != nil {
+				return nil, err
+			}
+			fields = append(fields, field{i, info})
+		}
+	}
+	return fields, nil
+}
+
 func genTypeInfo(typ reflect.Type) (info *typeinfo, err error) {
 	info = new(typeinfo)
 	if info.decoder, err = makeDecoder(typ); err != nil {
 		return nil, err
 	}
+	if info.writer, err = makeWriter(typ); err != nil {
+		return nil, err
+	}
 	return info, nil
 }