1 files changed, 207 insertions, 0 deletions
diff --git a/libgo/go/gob/encoder.go b/libgo/go/gob/encoder.go
new file mode 100644
index 000000000..8869b2629
--- /dev/null
+++ b/libgo/go/gob/encoder.go
@@ -0,0 +1,207 @@
+// 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.
+
+package gob
+
+import (
+	"bytes"
+	"io"
+	"os"
+	"reflect"
+	"sync"
+)
+
+// An Encoder manages the transmission of type and data information to the
+// other side of a connection.
+type Encoder struct {
+	mutex      sync.Mutex              // each item must be sent atomically
+	w          io.Writer               // where to send the data
+	sent       map[reflect.Type]typeId // which types we've already sent
+	state      *encoderState           // so we can encode integers, strings directly
+	countState *encoderState           // stage for writing counts
+	buf        []byte                  // for collecting the output.
+	err        os.Error
+}
+
+// NewEncoder returns a new encoder that will transmit on the io.Writer.
+func NewEncoder(w io.Writer) *Encoder {
+	enc := new(Encoder)
+	enc.w = w
+	enc.sent = make(map[reflect.Type]typeId)
+	enc.state = newEncoderState(enc, new(bytes.Buffer))
+	enc.countState = newEncoderState(enc, new(bytes.Buffer))
+	return enc
+}
+
+func (enc *Encoder) badType(rt reflect.Type) {
+	enc.setError(os.ErrorString("gob: can't encode type " + rt.String()))
+}
+
+func (enc *Encoder) setError(err os.Error) {
+	if enc.err == nil { // remember the first.
+		enc.err = err
+	}
+	enc.state.b.Reset()
+}
+
+// Send the data item preceded by a unsigned count of its length.
+func (enc *Encoder) send() {
+	// Encode the length.
+	enc.countState.encodeUint(uint64(enc.state.b.Len()))
+	// Build the buffer.
+	countLen := enc.countState.b.Len()
+	total := countLen + enc.state.b.Len()
+	if total > len(enc.buf) {
+		enc.buf = make([]byte, total+1000) // extra for growth
+	}
+	// Place the length before the data.
+	// TODO(r): avoid the extra copy here.
+	enc.countState.b.Read(enc.buf[0:countLen])
+	// Now the data.
+	enc.state.b.Read(enc.buf[countLen:total])
+	// Write the data.
+	_, err := enc.w.Write(enc.buf[0:total])
+	if err != nil {
+		enc.setError(err)
+	}
+}
+
+func (enc *Encoder) sendType(origt reflect.Type) (sent bool) {
+	// Drill down to the base type.
+	rt, _ := indirect(origt)
+
+	switch rt := rt.(type) {
+	default:
+		// Basic types and interfaces do not need to be described.
+		return
+	case *reflect.SliceType:
+		// If it's []uint8, don't send; it's considered basic.
+		if rt.Elem().Kind() == reflect.Uint8 {
+			return
+		}
+		// Otherwise we do send.
+		break
+	case *reflect.ArrayType:
+		// arrays must be sent so we know their lengths and element types.
+		break
+	case *reflect.MapType:
+		// maps must be sent so we know their lengths and key/value types.
+		break
+	case *reflect.StructType:
+		// structs must be sent so we know their fields.
+		break
+	case *reflect.ChanType, *reflect.FuncType:
+		// Probably a bad field in a struct.
+		enc.badType(rt)
+		return
+	}
+
+	// Have we already sent this type?  This time we ask about the base type.
+	if _, alreadySent := enc.sent[rt]; alreadySent {
+		return
+	}
+
+	// Need to send it.
+	typeLock.Lock()
+	info, err := getTypeInfo(rt)
+	typeLock.Unlock()
+	if err != nil {
+		enc.setError(err)
+		return
+	}
+	// Send the pair (-id, type)
+	// Id:
+	enc.state.encodeInt(-int64(info.id))
+	// Type:
+	enc.encode(enc.state.b, reflect.NewValue(info.wire))
+	enc.send()
+	if enc.err != nil {
+		return
+	}
+
+	// Remember we've sent this type.
+	enc.sent[rt] = info.id
+	// Remember we've sent the top-level, possibly indirect type too.
+	enc.sent[origt] = info.id
+	// Now send the inner types
+	switch st := rt.(type) {
+	case *reflect.StructType:
+		for i := 0; i < st.NumField(); i++ {
+			enc.sendType(st.Field(i).Type)
+		}
+	case reflect.ArrayOrSliceType:
+		enc.sendType(st.Elem())
+	}
+	return true
+}
+
+// Encode transmits the data item represented by the empty interface value,
+// guaranteeing that all necessary type information has been transmitted first.
+func (enc *Encoder) Encode(e interface{}) os.Error {
+	return enc.EncodeValue(reflect.NewValue(e))
+}
+
+// sendTypeId makes sure the remote side knows about this type.
+// It will send a descriptor if this is the first time the type has been
+// sent.  Regardless, it sends the id.
+func (enc *Encoder) sendTypeDescriptor(rt reflect.Type) {
+	// Make sure the type is known to the other side.
+	// First, have we already sent this type?
+	if _, alreadySent := enc.sent[rt]; !alreadySent {
+		// No, so send it.
+		sent := enc.sendType(rt)
+		if enc.err != nil {
+			return
+		}
+		// If the type info has still not been transmitted, it means we have
+		// a singleton basic type (int, []byte etc.) at top level.  We don't
+		// need to send the type info but we do need to update enc.sent.
+		if !sent {
+			typeLock.Lock()
+			info, err := getTypeInfo(rt)
+			typeLock.Unlock()
+			if err != nil {
+				enc.setError(err)
+				return
+			}
+			enc.sent[rt] = info.id
+		}
+	}
+
+	// Identify the type of this top-level value.
+	enc.state.encodeInt(int64(enc.sent[rt]))
+}
+
+// EncodeValue transmits the data item represented by the reflection value,
+// guaranteeing that all necessary type information has been transmitted first.
+func (enc *Encoder) EncodeValue(value reflect.Value) os.Error {
+	// Make sure we're single-threaded through here, so multiple
+	// goroutines can share an encoder.
+	enc.mutex.Lock()
+	defer enc.mutex.Unlock()
+
+	enc.err = nil
+	rt, _ := indirect(value.Type())
+
+	// Sanity check only: encoder should never come in with data present.
+	if enc.state.b.Len() > 0 || enc.countState.b.Len() > 0 {
+		enc.err = os.ErrorString("encoder: buffer not empty")
+		return enc.err
+	}
+
+	enc.sendTypeDescriptor(rt)
+	if enc.err != nil {
+		return enc.err
+	}
+
+	// Encode the object.
+	err := enc.encode(enc.state.b, value)
+	if err != nil {
+		enc.setError(err)
+	} else {
+		enc.send()
+	}
+
+	return enc.err
+}