Encode and decode engines for gobs.

R=rsc
DELTA=468  (292 added, 18 deleted, 158 changed)
OCL=31008
CL=31012

src/pkg/gob/codec_test.go

@@ -8,6 +8,7 @@ import (
 	"bytes";
 	"gob";
 	"os";
+	"reflect";
 	"testing";
 	"unsafe";
 )
@@ -106,35 +107,42 @@ func TestIntCodec(t *testing.T) {
 	verifyInt(-1<<63, t);	// a tricky case
 }
 
-
 // The result of encoding three true booleans with field numbers 0, 1, 2
-var boolResult = []byte{0x80, 0x81, 0x81, 0x81, 0x82, 0x81}
+var boolResult = []byte{0x81, 0x81, 0x81, 0x81, 0x81, 0x81}
 // The result of encoding three numbers = 17 with field numbers 0, 1, 2
-var signedResult = []byte{0x80, 0xa2, 0x81, 0xa2, 0x82, 0xa2}
+var signedResult = []byte{0x81, 0xa2, 0x81, 0xa2, 0x81, 0xa2}
-var unsignedResult = []byte{0x80, 0x91, 0x81, 0x91, 0x82, 0x91}
+var unsignedResult = []byte{0x81, 0x91, 0x81, 0x91, 0x81, 0x91}
-var floatResult = []byte{0x80, 0x40, 0xe2, 0x81, 0x40, 0xe2, 0x82, 0x40, 0xe2}
+var floatResult = []byte{0x81, 0x40, 0xe2, 0x81, 0x40, 0xe2, 0x81, 0x40, 0xe2}
+
+func newEncState(b *bytes.Buffer) *EncState {
+	b.Reset();
+	state := new(EncState);
+	state.w = b;
+	state.fieldnum = -1;
+	return state;
+}
 
 // Test instruction execution for encoding.
 // Do not run the machine yet; instead do individual instructions crafted by hand.
 func TestScalarEncInstructions(t *testing.T) {
 	var b = new(bytes.Buffer);
-	state := new(EncState);
 
 	// bool
 	{
-		b.Reset();
 		v := true;
 		pv := &v;
 		ppv := &pv;
 		data := (struct { a bool; b *bool; c **bool }){ v, pv, ppv };
 		instr := &encInstr{ encBool, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -152,13 +160,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a int; b *int; c **int }){ v, pv, ppv };
 		instr := &encInstr{ encInt, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -176,13 +186,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a uint; b *uint; c **uint }){ v, pv, ppv };
 		instr := &encInstr{ encUint, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -200,13 +212,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a int8; b *int8; c **int8 }){ v, pv, ppv };
 		instr := &encInstr{ encInt, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -224,13 +238,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a uint8; b *uint8; c **uint8 }){ v, pv, ppv };
 		instr := &encInstr{ encUint, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -248,13 +264,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a int16; b *int16; c **int16 }){ v, pv, ppv };
 		instr := &encInstr{ encInt16, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -272,13 +290,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a uint16; b *uint16; c **uint16 }){ v, pv, ppv };
 		instr := &encInstr{ encUint16, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -296,13 +316,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a int32; b *int32; c **int32 }){ v, pv, ppv };
 		instr := &encInstr{ encInt32, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -320,13 +342,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a uint32; b *uint32; c **uint32 }){ v, pv, ppv };
 		instr := &encInstr{ encUint32, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -344,13 +368,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a int64; b *int64; c **int64 }){ v, pv, ppv };
 		instr := &encInstr{ encInt64, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -368,13 +394,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a uint64; b *uint64; c **uint64 }){ v, pv, ppv };
 		instr := &encInstr{ encUint, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -392,13 +420,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a float; b *float; c **float }){ v, pv, ppv };
 		instr := &encInstr{ encFloat, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -416,13 +446,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a float32; b *float32; c **float32 }){ v, pv, ppv };
 		instr := &encInstr{ encFloat32, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -440,13 +472,15 @@ func TestScalarEncInstructions(t *testing.T) {
 		ppv := &pv;
 		data := (struct { a float64; b *float64; c **float64 }){ v, pv, ppv };
 		instr := &encInstr{ encFloat64, 0, 0, 0 };
-		state.w = b;
+		state := newEncState(b);
 		state.base = uintptr(unsafe.Pointer(&data));
 		instr.op(instr, state);
+		state.fieldnum = 0;
 		instr.field = 1;
 		instr.indir = 1;
 		instr.offset = uintptr(unsafe.Offsetof(data.b));
 		instr.op(instr, state);
+		state.fieldnum = 1;
 		instr.field = 2;
 		instr.indir = 2;
 		instr.offset = uintptr(unsafe.Offsetof(data.c));
@@ -462,22 +496,28 @@ func expectField(n int, state *DecState, t *testing.T) {
 	if state.err != nil {
 		t.Fatalf("decoding field number %d: %v", n, state.err);
 	}
-	if v != n {
+	if v + state.fieldnum != n {
 		t.Fatalf("decoding field number %d, got %d", n, v);
 	}
+	state.fieldnum = n;
+}
+
+func newDecState(data []byte) *DecState {
+	state := new(DecState);
+	state.r = bytes.NewBuffer(data);
+	state.fieldnum = -1;
+	return state;
 }
 
 // Test instruction execution for decoding.
 // Do not run the machine yet; instead do individual instructions crafted by hand.
 func TestScalarDecInstructions(t *testing.T) {
-	state := new(DecState);
 
 	// bool
 	{
-		b := bytes.NewBuffer(boolResult);
 		var data struct { a bool; b *bool; c **bool };
 		instr := &decInstr{ decBool, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(boolResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -504,10 +544,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// int
 	{
-		b := bytes.NewBuffer(signedResult);
 		var data struct { a int; b *int; c **int };
 		instr := &decInstr{ decInt, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(signedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -534,10 +573,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// uint
 	{
-		b := bytes.NewBuffer(unsignedResult);
 		var data struct { a uint; b *uint; c **uint };
 		instr := &decInstr{ decUint, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(unsignedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -564,10 +602,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// int8
 	{
-		b := bytes.NewBuffer(signedResult);
 		var data struct { a int8; b *int8; c **int8 };
 		instr := &decInstr{ decInt8, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(signedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -594,10 +631,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// uint8
 	{
-		b := bytes.NewBuffer(unsignedResult);
 		var data struct { a uint8; b *uint8; c **uint8 };
 		instr := &decInstr{ decUint8, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(unsignedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -624,10 +660,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// int16
 	{
-		b := bytes.NewBuffer(signedResult);
 		var data struct { a int16; b *int16; c **int16 };
 		instr := &decInstr{ decInt16, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(signedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -654,10 +689,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// uint16
 	{
-		b := bytes.NewBuffer(unsignedResult);
 		var data struct { a uint16; b *uint16; c **uint16 };
 		instr := &decInstr{ decUint16, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(unsignedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -684,10 +718,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// int32
 	{
-		b := bytes.NewBuffer(signedResult);
 		var data struct { a int32; b *int32; c **int32 };
 		instr := &decInstr{ decInt32, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(signedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -714,10 +747,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// uint32
 	{
-		b := bytes.NewBuffer(unsignedResult);
 		var data struct { a uint32; b *uint32; c **uint32 };
 		instr := &decInstr{ decUint32, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(unsignedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -744,10 +776,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// int64
 	{
-		b := bytes.NewBuffer(signedResult);
 		var data struct { a int64; b *int64; c **int64 };
 		instr := &decInstr{ decInt64, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(signedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -774,10 +805,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// uint64
 	{
-		b := bytes.NewBuffer(unsignedResult);
 		var data struct { a uint64; b *uint64; c **uint64 };
 		instr := &decInstr{ decUint64, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(unsignedResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -804,10 +834,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// float
 	{
-		b := bytes.NewBuffer(floatResult);
 		var data struct { a float; b *float; c **float };
 		instr := &decInstr{ decFloat, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(floatResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -834,10 +863,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// float32
 	{
-		b := bytes.NewBuffer(floatResult);
 		var data struct { a float32; b *float32; c **float32 };
 		instr := &decInstr{ decFloat32, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(floatResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -864,10 +892,9 @@ func TestScalarDecInstructions(t *testing.T) {
 
 	// float64
 	{
-		b := bytes.NewBuffer(floatResult);
 		var data struct { a float64; b *float64; c **float64 };
 		instr := &decInstr{ decFloat64, 0, 0, 0 };
-		state.r = b;
+		state := newDecState(floatResult);
 		state.base = uintptr(unsafe.Pointer(&data));
 		expectField(0, state, t);
 		instr.op(instr, state);
@@ -892,3 +919,18 @@ func TestScalarDecInstructions(t *testing.T) {
 		}
 	}
 }
+
+type T1 struct {
+	a, b,c int
+}
+
+func TestEncode(t *testing.T) {
+	t1 := &T1{17,18,-5};
+	b := new(bytes.Buffer);
+	Encode(b, t1);
+	var _t1 T1;
+	Decode(b, &_t1);
+	if !reflect.DeepEqual(t1, &_t1) {
+		t.Errorf("encode expected %v got %v", *t1, _t1);
+	}
+}

src/pkg/gob/decode.go

@@ -5,9 +5,11 @@
 package gob
 
 import (
+	"gob";
 	"io";
 	"math";
 	"os";
+	"reflect";
 	"unsafe";
 )
 
@@ -16,6 +18,7 @@ type DecState struct {
 	r	io.Reader;
 	err	os.Error;
 	base	uintptr;
+	fieldnum	int;	// the last field number read.
 	buf [1]byte;	// buffer used by the decoder; here to avoid allocation.
 }
 
@@ -333,3 +336,114 @@ func decFloat64(i *decInstr, state *DecState) {
 		*(*float64)(p) = v;
 	}
 }
+
+// Execution engine
+
+// The encoder engine is an array of instructions indexed by field number of the incoming
+// data.  It is executed with random access according to field number.
+type decEngine struct {
+	instr	[]decInstr
+}
+
+var decEngineMap = make(map[reflect.Type] *decEngine)
+var decOp = map[int] func(*decInstr, *DecState) {
+	 reflect.BoolKind: decBool,
+	 reflect.IntKind: decInt,
+	 reflect.Int8Kind: decInt8,
+	 reflect.Int16Kind: decInt16,
+	 reflect.Int32Kind: decInt32,
+	 reflect.Int64Kind: decInt64,
+	 reflect.UintKind: decUint,
+	 reflect.Uint8Kind: decUint8,
+	 reflect.Uint16Kind: decUint16,
+	 reflect.Uint32Kind: decUint32,
+	 reflect.Uint64Kind: decUint64,
+	 reflect.FloatKind: decFloat,
+	 reflect.Float32Kind: decFloat32,
+	 reflect.Float64Kind: decFloat64,
+}
+
+func compileDec(rt reflect.Type, typ Type) *decEngine {
+	srt, ok1 := rt.(reflect.StructType);
+	styp, ok2 := typ.(*structType);
+	if !ok1 || !ok2 {
+		panicln("TODO: can't handle non-structs");
+	}
+	engine := new(decEngine);
+	engine.instr = make([]decInstr, len(styp.field));
+	for fieldnum := 0; fieldnum < len(styp.field); fieldnum++ {
+		field := styp.field[fieldnum];
+		// TODO(r): verify compatibility with corresponding field of data.
+		// For now, assume perfect correspondence between struct and gob.
+		_name, ftyp, _tag, offset := srt.Field(fieldnum);
+		// How many indirections to the underlying data?
+		indir := 0;
+		for {
+			pt, ok := ftyp.(reflect.PtrType);
+			if !ok {
+				break
+			}
+			ftyp = pt.Sub();
+			indir++;
+		}
+		op, ok := decOp[ftyp.Kind()];
+		if !ok {
+			panicln("can't handle decode for type", ftyp.String());
+		}
+		engine.instr[fieldnum] = decInstr{op, fieldnum, indir, uintptr(offset)};
+	}
+	return engine;
+}
+
+
+func getDecEngine(rt reflect.Type) *decEngine {
+	engine, ok := decEngineMap[rt];
+	if !ok {
+		return compileDec(rt, newType(rt.Name(), rt));
+		decEngineMap[rt] = engine;
+	}
+	return engine;
+}
+
+func (engine *decEngine) decode(r io.Reader, v reflect.Value) os.Error {
+	sv, ok := v.(reflect.StructValue);
+	if !ok {
+		panicln("decoder can't handle non-struct values yet");
+	}
+	state := new(DecState);
+	state.r = r;
+	state.base = uintptr(sv.Addr());
+	state.fieldnum = -1;
+	for state.err == nil {
+		delta := int(DecodeUint(state));
+		if state.err != nil || delta == 0 {	// struct terminator is zero delta fieldnum
+			break
+		}
+		fieldnum := state.fieldnum + delta;
+		if fieldnum >= len(engine.instr) {
+			panicln("TODO(r): need to handle unknown data");
+		}
+		instr := &engine.instr[fieldnum];
+		instr.op(instr, state);
+		state.fieldnum = fieldnum;
+	}
+	return state.err
+}
+
+func Decode(r io.Reader, e interface{}) os.Error {
+	// Dereference down to the underlying object.
+	rt := reflect.Typeof(e);
+	v := reflect.NewValue(e);
+	for {
+		pt, ok := rt.(reflect.PtrType);
+		if !ok {
+			break
+		}
+		rt = pt.Sub();
+		v = reflect.Indirect(v);
+	}
+	typeLock.Lock();
+	engine := getDecEngine(rt);
+	typeLock.Unlock();
+	return engine.decode(r, v);
+}

src/pkg/gob/encode.go

@@ -5,17 +5,24 @@
 package gob
 
 import (
+	"gob";
 	"io";
 	"math";
 	"os";
+	"reflect";
+	"sync";
 	"unsafe";
 )
 
 // 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
+// 0 terminates the structure.
 type EncState struct {
 	w	io.Writer;
 	base	uintptr;	// the base address of the data structure being written
 	err	os.Error;	// error encountered during encoding;
+	fieldnum	int;	// the last field number written.
 	buf [16]byte;	// buffer used by the encoder; here to avoid allocation.
 }
 
@@ -86,7 +93,7 @@ func encBool(i *encInstr, state *EncState) {
 	}
 	b := *(*bool)(p);
 	if b {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, 1);
 	}
 }
@@ -100,7 +107,7 @@ func encInt(i *encInstr, state *EncState) {
 	}
 	v := int64(*(*int)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeInt(state, v);
 	}
 }
@@ -114,7 +121,7 @@ func encUint(i *encInstr, state *EncState) {
 	}
 	v := uint64(*(*uint)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -128,7 +135,7 @@ func encInt8(i *encInstr, state *EncState) {
 	}
 	v := int64(*(*int8)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeInt(state, v);
 	}
 }
@@ -142,7 +149,7 @@ func encUint8(i *encInstr, state *EncState) {
 	}
 	v := uint64(*(*uint8)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -156,7 +163,7 @@ func encInt16(i *encInstr, state *EncState) {
 	}
 	v := int64(*(*int16)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeInt(state, v);
 	}
 }
@@ -170,7 +177,7 @@ func encUint16(i *encInstr, state *EncState) {
 	}
 	v := uint64(*(*uint16)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -184,7 +191,7 @@ func encInt32(i *encInstr, state *EncState) {
 	}
 	v := int64(*(*int32)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeInt(state, v);
 	}
 }
@@ -198,7 +205,7 @@ func encUint32(i *encInstr, state *EncState) {
 	}
 	v := uint64(*(*uint32)(p));
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -212,7 +219,7 @@ func encInt64(i *encInstr, state *EncState) {
 	}
 	v := *(*int64)(p);
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeInt(state, v);
 	}
 }
@@ -226,7 +233,7 @@ func encUint64(i *encInstr, state *EncState) {
 	}
 	v := *(*uint64)(p);
 	if v != 0 {
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -257,7 +264,7 @@ func encFloat(i *encInstr, state *EncState) {
 	f := float(*(*float)(p));
 	if f != 0 {
 		v := floatBits(float64(f));
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -272,7 +279,7 @@ func encFloat32(i *encInstr, state *EncState) {
 	f := float32(*(*float32)(p));
 	if f != 0 {
 		v := floatBits(float64(f));
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
@@ -287,7 +294,118 @@ func encFloat64(i *encInstr, state *EncState) {
 	f := *(*float64)(p);
 	if f != 0 {
 		v := floatBits(f);
-		EncodeUint(state, uint64(i.field));
+		EncodeUint(state, uint64(i.field - state.fieldnum));
 		EncodeUint(state, v);
 	}
 }
+
+// The end of a struct is marked by a delta field number of 0.
+func encStructTerminator(i *encInstr, state *EncState) {
+	EncodeUint(state, 0);
+}
+
+// Execution engine
+
+// The encoder engine is an array of instructions indexed by field number of the encoding
+// data, typically a struct.  It is executed top to bottom, walking the struct.
+type encEngine struct {
+	instr	[]encInstr
+}
+
+var encEngineMap = make(map[reflect.Type] *encEngine)
+var encOp = map[int] func(*encInstr, *EncState) {
+	 reflect.BoolKind: encBool,
+	 reflect.IntKind: encInt,
+	 reflect.Int8Kind: encInt8,
+	 reflect.Int16Kind: encInt16,
+	 reflect.Int32Kind: encInt32,
+	 reflect.Int64Kind: encInt64,
+	 reflect.UintKind: encUint,
+	 reflect.Uint8Kind: encUint8,
+	 reflect.Uint16Kind: encUint16,
+	 reflect.Uint32Kind: encUint32,
+	 reflect.Uint64Kind: encUint64,
+	 reflect.FloatKind: encFloat,
+	 reflect.Float32Kind: encFloat32,
+	 reflect.Float64Kind: encFloat64,
+}
+
+// The local Type was compiled from the actual value, so we know
+// it's compatible.
+// TODO(r): worth checking?  typ is unused here.
+func compileEnc(rt reflect.Type, typ Type) *encEngine {
+	srt, ok := rt.(reflect.StructType);
+	if !ok {
+		panicln("TODO: can't handle non-structs");
+	}
+	engine := new(encEngine);
+	engine.instr = make([]encInstr, srt.Len()+1);	// +1 for terminator
+	for fieldnum := 0; fieldnum < srt.Len(); fieldnum++ {
+		_name, ftyp, _tag, offset := srt.Field(fieldnum);
+		// How many indirections to the underlying data?
+		indir := 0;
+		for {
+			pt, ok := ftyp.(reflect.PtrType);
+			if !ok {
+				break
+			}
+			ftyp = pt.Sub();
+			indir++;
+		}
+		op, ok := encOp[ftyp.Kind()];
+		if !ok {
+			panicln("encode can't handle type", ftyp.String());
+		}
+		engine.instr[fieldnum] = encInstr{op, fieldnum, indir, uintptr(offset)};
+	}
+	engine.instr[srt.Len()] = encInstr{encStructTerminator, 0, 0, 0};
+	return engine;
+}
+
+// typeLock must be held.
+func getEncEngine(rt reflect.Type) *encEngine {
+	engine, ok := encEngineMap[rt];
+	if !ok {
+		engine = compileEnc(rt, newType(rt.Name(), rt));
+		encEngineMap[rt] = engine;
+	}
+	return engine
+}
+
+func (engine *encEngine) encode(w io.Writer, v reflect.Value) os.Error {
+	sv, ok := v.(reflect.StructValue);
+	if !ok {
+		panicln("encoder can't handle non-struct values yet");
+	}
+	state := new(EncState);
+	state.w = w;
+	state.base = uintptr(sv.Addr());
+	state.fieldnum = -1;
+	for i := 0; i < len(engine.instr); i++ {
+		instr := &engine.instr[i];
+		instr.op(instr, state);
+		if state.err != nil {
+			break
+		}
+		state.fieldnum = i;
+	}
+	return state.err
+}
+
+func Encode(w io.Writer, e interface{}) os.Error {
+	// Dereference down to the underlying object.
+	rt := reflect.Typeof(e);
+	v := reflect.NewValue(e);
+	for {
+		pt, ok := rt.(reflect.PtrType);
+		if !ok {
+			break
+		}
+		rt = pt.Sub();
+		v = reflect.Indirect(v);
+	}
+	typeLock.Lock();
+	engine := getEncEngine(rt);
+	typeLock.Unlock();
+	return engine.encode(w, v);
+}