1 files changed, 705 insertions, 0 deletions
diff --git a/src/encoding/gob/encode.go b/src/encoding/gob/encode.go
new file mode 100644
index 0000000..8f8f170
--- /dev/null
+++ b/src/encoding/gob/encode.go
@@ -0,0 +1,705 @@
+// 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.
+
+//go:generate go run encgen.go -output enc_helpers.go
+
+package gob
+
+import (
+	"encoding"
+	"encoding/binary"
+	"math"
+	"math/bits"
+	"reflect"
+	"sync"
+)
+
+const uint64Size = 8
+
+type encHelper func(state *encoderState, v reflect.Value) bool
+
+// encoderState is 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 encoderState struct {
+	enc      *Encoder
+	b        *encBuffer
+	sendZero bool                 // encoding an array element or map key/value pair; send zero values
+	fieldnum int                  // the last field number written.
+	buf      [1 + uint64Size]byte // buffer used by the encoder; here to avoid allocation.
+	next     *encoderState        // for free list
+}
+
+// encBuffer is an extremely simple, fast implementation of a write-only byte buffer.
+// It never returns a non-nil error, but Write returns an error value so it matches io.Writer.
+type encBuffer struct {
+	data    []byte
+	scratch [64]byte
+}
+
+var encBufferPool = sync.Pool{
+	New: func() interface{} {
+		e := new(encBuffer)
+		e.data = e.scratch[0:0]
+		return e
+	},
+}
+
+func (e *encBuffer) writeByte(c byte) {
+	e.data = append(e.data, c)
+}
+
+func (e *encBuffer) Write(p []byte) (int, error) {
+	e.data = append(e.data, p...)
+	return len(p), nil
+}
+
+func (e *encBuffer) WriteString(s string) {
+	e.data = append(e.data, s...)
+}
+
+func (e *encBuffer) Len() int {
+	return len(e.data)
+}
+
+func (e *encBuffer) Bytes() []byte {
+	return e.data
+}
+
+func (e *encBuffer) Reset() {
+	if len(e.data) >= tooBig {
+		e.data = e.scratch[0:0]
+	} else {
+		e.data = e.data[0:0]
+	}
+}
+
+func (enc *Encoder) newEncoderState(b *encBuffer) *encoderState {
+	e := enc.freeList
+	if e == nil {
+		e = new(encoderState)
+		e.enc = enc
+	} else {
+		enc.freeList = e.next
+	}
+	e.sendZero = false
+	e.fieldnum = 0
+	e.b = b
+	if len(b.data) == 0 {
+		b.data = b.scratch[0:0]
+	}
+	return e
+}
+
+func (enc *Encoder) freeEncoderState(e *encoderState) {
+	e.next = enc.freeList
+	enc.freeList = e
+}
+
+// Unsigned integers have a two-state encoding. If the number is less
+// than 128 (0 through 0x7F), its value is written directly.
+// Otherwise the value is written in big-endian byte order preceded
+// by the byte length, negated.
+
+// encodeUint writes an encoded unsigned integer to state.b.
+func (state *encoderState) encodeUint(x uint64) {
+	if x <= 0x7F {
+		state.b.writeByte(uint8(x))
+		return
+	}
+
+	binary.BigEndian.PutUint64(state.buf[1:], x)
+	bc := bits.LeadingZeros64(x) >> 3      // 8 - bytelen(x)
+	state.buf[bc] = uint8(bc - uint64Size) // and then we subtract 8 to get -bytelen(x)
+
+	state.b.Write(state.buf[bc : uint64Size+1])
+}
+
+// encodeInt writes an encoded signed integer to state.w.
+// The low bit of the encoding says whether to bit complement the (other bits of the)
+// uint to recover the int.
+func (state *encoderState) encodeInt(i int64) {
+	var x uint64
+	if i < 0 {
+		x = uint64(^i<<1) | 1
+	} else {
+		x = uint64(i << 1)
+	}
+	state.encodeUint(x)
+}
+
+// encOp is the signature of an encoding operator for a given type.
+type encOp func(i *encInstr, state *encoderState, v reflect.Value)
+
+// The 'instructions' of the encoding machine
+type encInstr struct {
+	op    encOp
+	field int   // field number in input
+	index []int // struct index
+	indir int   // how many pointer indirections to reach the value in the struct
+}
+
+// update emits a field number and updates the state to record its value for delta encoding.
+// If the instruction pointer is nil, it does nothing
+func (state *encoderState) update(instr *encInstr) {
+	if instr != nil {
+		state.encodeUint(uint64(instr.field - state.fieldnum))
+		state.fieldnum = instr.field
+	}
+}
+
+// Each encoder for a composite is responsible for handling any
+// indirections associated with the elements of the data structure.
+// If any pointer so reached is nil, no bytes are written. If the
+// data item is zero, no bytes are written. Single values - ints,
+// strings etc. - are indirected before calling their encoders.
+// Otherwise, the output (for a scalar) is the field number, as an
+// encoded integer, followed by the field data in its appropriate
+// format.
+
+// encIndirect dereferences pv indir times and returns the result.
+func encIndirect(pv reflect.Value, indir int) reflect.Value {
+	for ; indir > 0; indir-- {
+		if pv.IsNil() {
+			break
+		}
+		pv = pv.Elem()
+	}
+	return pv
+}
+
+// encBool encodes the bool referenced by v as an unsigned 0 or 1.
+func encBool(i *encInstr, state *encoderState, v reflect.Value) {
+	b := v.Bool()
+	if b || state.sendZero {
+		state.update(i)
+		if b {
+			state.encodeUint(1)
+		} else {
+			state.encodeUint(0)
+		}
+	}
+}
+
+// encInt encodes the signed integer (int int8 int16 int32 int64) referenced by v.
+func encInt(i *encInstr, state *encoderState, v reflect.Value) {
+	value := v.Int()
+	if value != 0 || state.sendZero {
+		state.update(i)
+		state.encodeInt(value)
+	}
+}
+
+// encUint encodes the unsigned integer (uint uint8 uint16 uint32 uint64 uintptr) referenced by v.
+func encUint(i *encInstr, state *encoderState, v reflect.Value) {
+	value := v.Uint()
+	if value != 0 || state.sendZero {
+		state.update(i)
+		state.encodeUint(value)
+	}
+}
+
+// floatBits returns a uint64 holding the bits of a floating-point number.
+// Floating-point numbers are transmitted as uint64s holding the bits
+// of the underlying representation. They are sent byte-reversed, with
+// the exponent end coming out first, so integer floating point numbers
+// (for example) transmit more compactly. This routine does the
+// swizzling.
+func floatBits(f float64) uint64 {
+	u := math.Float64bits(f)
+	return bits.ReverseBytes64(u)
+}
+
+// encFloat encodes the floating point value (float32 float64) referenced by v.
+func encFloat(i *encInstr, state *encoderState, v reflect.Value) {
+	f := v.Float()
+	if f != 0 || state.sendZero {
+		bits := floatBits(f)
+		state.update(i)
+		state.encodeUint(bits)
+	}
+}
+
+// encComplex encodes the complex value (complex64 complex128) referenced by v.
+// Complex numbers are just a pair of floating-point numbers, real part first.
+func encComplex(i *encInstr, state *encoderState, v reflect.Value) {
+	c := v.Complex()
+	if c != 0+0i || state.sendZero {
+		rpart := floatBits(real(c))
+		ipart := floatBits(imag(c))
+		state.update(i)
+		state.encodeUint(rpart)
+		state.encodeUint(ipart)
+	}
+}
+
+// encUint8Array encodes the byte array referenced by v.
+// Byte arrays are encoded as an unsigned count followed by the raw bytes.
+func encUint8Array(i *encInstr, state *encoderState, v reflect.Value) {
+	b := v.Bytes()
+	if len(b) > 0 || state.sendZero {
+		state.update(i)
+		state.encodeUint(uint64(len(b)))
+		state.b.Write(b)
+	}
+}
+
+// encString encodes the string referenced by v.
+// Strings are encoded as an unsigned count followed by the raw bytes.
+func encString(i *encInstr, state *encoderState, v reflect.Value) {
+	s := v.String()
+	if len(s) > 0 || state.sendZero {
+		state.update(i)
+		state.encodeUint(uint64(len(s)))
+		state.b.WriteString(s)
+	}
+}
+
+// encStructTerminator encodes the end of an encoded struct
+// as delta field number of 0.
+func encStructTerminator(i *encInstr, state *encoderState, v reflect.Value) {
+	state.encodeUint(0)
+}
+
+// Execution engine
+
+// encEngine 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
+}
+
+const singletonField = 0
+
+// valid reports whether the value is valid and a non-nil pointer.
+// (Slices, maps, and chans take care of themselves.)
+func valid(v reflect.Value) bool {
+	switch v.Kind() {
+	case reflect.Invalid:
+		return false
+	case reflect.Ptr:
+		return !v.IsNil()
+	}
+	return true
+}
+
+// encodeSingle encodes a single top-level non-struct value.
+func (enc *Encoder) encodeSingle(b *encBuffer, engine *encEngine, value reflect.Value) {
+	state := enc.newEncoderState(b)
+	defer enc.freeEncoderState(state)
+	state.fieldnum = singletonField
+	// There is no surrounding struct to frame the transmission, so we must
+	// generate data even if the item is zero. To do this, set sendZero.
+	state.sendZero = true
+	instr := &engine.instr[singletonField]
+	if instr.indir > 0 {
+		value = encIndirect(value, instr.indir)
+	}
+	if valid(value) {
+		instr.op(instr, state, value)
+	}
+}
+
+// encodeStruct encodes a single struct value.
+func (enc *Encoder) encodeStruct(b *encBuffer, engine *encEngine, value reflect.Value) {
+	if !valid(value) {
+		return
+	}
+	state := enc.newEncoderState(b)
+	defer enc.freeEncoderState(state)
+	state.fieldnum = -1
+	for i := 0; i < len(engine.instr); i++ {
+		instr := &engine.instr[i]
+		if i >= value.NumField() {
+			// encStructTerminator
+			instr.op(instr, state, reflect.Value{})
+			break
+		}
+		field := value.FieldByIndex(instr.index)
+		if instr.indir > 0 {
+			field = encIndirect(field, instr.indir)
+			// TODO: Is field guaranteed valid? If so we could avoid this check.
+			if !valid(field) {
+				continue
+			}
+		}
+		instr.op(instr, state, field)
+	}
+}
+
+// encodeArray encodes an array.
+func (enc *Encoder) encodeArray(b *encBuffer, value reflect.Value, op encOp, elemIndir int, length int, helper encHelper) {
+	state := enc.newEncoderState(b)
+	defer enc.freeEncoderState(state)
+	state.fieldnum = -1
+	state.sendZero = true
+	state.encodeUint(uint64(length))
+	if helper != nil && helper(state, value) {
+		return
+	}
+	for i := 0; i < length; i++ {
+		elem := value.Index(i)
+		if elemIndir > 0 {
+			elem = encIndirect(elem, elemIndir)
+			// TODO: Is elem guaranteed valid? If so we could avoid this check.
+			if !valid(elem) {
+				errorf("encodeArray: nil element")
+			}
+		}
+		op(nil, state, elem)
+	}
+}
+
+// encodeReflectValue is a helper for maps. It encodes the value v.
+func encodeReflectValue(state *encoderState, v reflect.Value, op encOp, indir int) {
+	for i := 0; i < indir && v.IsValid(); i++ {
+		v = reflect.Indirect(v)
+	}
+	if !v.IsValid() {
+		errorf("encodeReflectValue: nil element")
+	}
+	op(nil, state, v)
+}
+
+// encodeMap encodes a map as unsigned count followed by key:value pairs.
+func (enc *Encoder) encodeMap(b *encBuffer, mv reflect.Value, keyOp, elemOp encOp, keyIndir, elemIndir int) {
+	state := enc.newEncoderState(b)
+	state.fieldnum = -1
+	state.sendZero = true
+	keys := mv.MapKeys()
+	state.encodeUint(uint64(len(keys)))
+	for _, key := range keys {
+		encodeReflectValue(state, key, keyOp, keyIndir)
+		encodeReflectValue(state, mv.MapIndex(key), elemOp, elemIndir)
+	}
+	enc.freeEncoderState(state)
+}
+
+// encodeInterface encodes the interface value iv.
+// To send an interface, we send a string identifying the concrete type, followed
+// by the type identifier (which might require defining that type right now), followed
+// by the concrete value. A nil value gets sent as the empty string for the name,
+// followed by no value.
+func (enc *Encoder) encodeInterface(b *encBuffer, iv reflect.Value) {
+	// Gobs can encode nil interface values but not typed interface
+	// values holding nil pointers, since nil pointers point to no value.
+	elem := iv.Elem()
+	if elem.Kind() == reflect.Ptr && elem.IsNil() {
+		errorf("gob: cannot encode nil pointer of type %s inside interface", iv.Elem().Type())
+	}
+	state := enc.newEncoderState(b)
+	state.fieldnum = -1
+	state.sendZero = true
+	if iv.IsNil() {
+		state.encodeUint(0)
+		return
+	}
+
+	ut := userType(iv.Elem().Type())
+	namei, ok := concreteTypeToName.Load(ut.base)
+	if !ok {
+		errorf("type not registered for interface: %s", ut.base)
+	}
+	name := namei.(string)
+
+	// Send the name.
+	state.encodeUint(uint64(len(name)))
+	state.b.WriteString(name)
+	// Define the type id if necessary.
+	enc.sendTypeDescriptor(enc.writer(), state, ut)
+	// Send the type id.
+	enc.sendTypeId(state, ut)
+	// Encode the value into a new buffer. Any nested type definitions
+	// should be written to b, before the encoded value.
+	enc.pushWriter(b)
+	data := encBufferPool.Get().(*encBuffer)
+	data.Write(spaceForLength)
+	enc.encode(data, elem, ut)
+	if enc.err != nil {
+		error_(enc.err)
+	}
+	enc.popWriter()
+	enc.writeMessage(b, data)
+	data.Reset()
+	encBufferPool.Put(data)
+	if enc.err != nil {
+		error_(enc.err)
+	}
+	enc.freeEncoderState(state)
+}
+
+// isZero reports whether the value is the zero of its type.
+func isZero(val reflect.Value) bool {
+	switch val.Kind() {
+	case reflect.Array:
+		for i := 0; i < val.Len(); i++ {
+			if !isZero(val.Index(i)) {
+				return false
+			}
+		}
+		return true
+	case reflect.Map, reflect.Slice, reflect.String:
+		return val.Len() == 0
+	case reflect.Bool:
+		return !val.Bool()
+	case reflect.Complex64, reflect.Complex128:
+		return val.Complex() == 0
+	case reflect.Chan, reflect.Func, reflect.Interface, reflect.Ptr:
+		return val.IsNil()
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return val.Int() == 0
+	case reflect.Float32, reflect.Float64:
+		return val.Float() == 0
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+		return val.Uint() == 0
+	case reflect.Struct:
+		for i := 0; i < val.NumField(); i++ {
+			if !isZero(val.Field(i)) {
+				return false
+			}
+		}
+		return true
+	}
+	panic("unknown type in isZero " + val.Type().String())
+}
+
+// encGobEncoder encodes a value that implements the GobEncoder interface.
+// The data is sent as a byte array.
+func (enc *Encoder) encodeGobEncoder(b *encBuffer, ut *userTypeInfo, v reflect.Value) {
+	// TODO: should we catch panics from the called method?
+
+	var data []byte
+	var err error
+	// We know it's one of these.
+	switch ut.externalEnc {
+	case xGob:
+		data, err = v.Interface().(GobEncoder).GobEncode()
+	case xBinary:
+		data, err = v.Interface().(encoding.BinaryMarshaler).MarshalBinary()
+	case xText:
+		data, err = v.Interface().(encoding.TextMarshaler).MarshalText()
+	}
+	if err != nil {
+		error_(err)
+	}
+	state := enc.newEncoderState(b)
+	state.fieldnum = -1
+	state.encodeUint(uint64(len(data)))
+	state.b.Write(data)
+	enc.freeEncoderState(state)
+}
+
+var encOpTable = [...]encOp{
+	reflect.Bool:       encBool,
+	reflect.Int:        encInt,
+	reflect.Int8:       encInt,
+	reflect.Int16:      encInt,
+	reflect.Int32:      encInt,
+	reflect.Int64:      encInt,
+	reflect.Uint:       encUint,
+	reflect.Uint8:      encUint,
+	reflect.Uint16:     encUint,
+	reflect.Uint32:     encUint,
+	reflect.Uint64:     encUint,
+	reflect.Uintptr:    encUint,
+	reflect.Float32:    encFloat,
+	reflect.Float64:    encFloat,
+	reflect.Complex64:  encComplex,
+	reflect.Complex128: encComplex,
+	reflect.String:     encString,
+}
+
+// encOpFor returns (a pointer to) the encoding op for the base type under rt and
+// the indirection count to reach it.
+func encOpFor(rt reflect.Type, inProgress map[reflect.Type]*encOp, building map[*typeInfo]bool) (*encOp, int) {
+	ut := userType(rt)
+	// If the type implements GobEncoder, we handle it without further processing.
+	if ut.externalEnc != 0 {
+		return gobEncodeOpFor(ut)
+	}
+	// If this type is already in progress, it's a recursive type (e.g. map[string]*T).
+	// Return the pointer to the op we're already building.
+	if opPtr := inProgress[rt]; opPtr != nil {
+		return opPtr, ut.indir
+	}
+	typ := ut.base
+	indir := ut.indir
+	k := typ.Kind()
+	var op encOp
+	if int(k) < len(encOpTable) {
+		op = encOpTable[k]
+	}
+	if op == nil {
+		inProgress[rt] = &op
+		// Special cases
+		switch t := typ; t.Kind() {
+		case reflect.Slice:
+			if t.Elem().Kind() == reflect.Uint8 {
+				op = encUint8Array
+				break
+			}
+			// Slices have a header; we decode it to find the underlying array.
+			elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+			helper := encSliceHelper[t.Elem().Kind()]
+			op = func(i *encInstr, state *encoderState, slice reflect.Value) {
+				if !state.sendZero && slice.Len() == 0 {
+					return
+				}
+				state.update(i)
+				state.enc.encodeArray(state.b, slice, *elemOp, elemIndir, slice.Len(), helper)
+			}
+		case reflect.Array:
+			// True arrays have size in the type.
+			elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+			helper := encArrayHelper[t.Elem().Kind()]
+			op = func(i *encInstr, state *encoderState, array reflect.Value) {
+				state.update(i)
+				state.enc.encodeArray(state.b, array, *elemOp, elemIndir, array.Len(), helper)
+			}
+		case reflect.Map:
+			keyOp, keyIndir := encOpFor(t.Key(), inProgress, building)
+			elemOp, elemIndir := encOpFor(t.Elem(), inProgress, building)
+			op = func(i *encInstr, state *encoderState, mv reflect.Value) {
+				// We send zero-length (but non-nil) maps because the
+				// receiver might want to use the map.  (Maps don't use append.)
+				if !state.sendZero && mv.IsNil() {
+					return
+				}
+				state.update(i)
+				state.enc.encodeMap(state.b, mv, *keyOp, *elemOp, keyIndir, elemIndir)
+			}
+		case reflect.Struct:
+			// Generate a closure that calls out to the engine for the nested type.
+			getEncEngine(userType(typ), building)
+			info := mustGetTypeInfo(typ)
+			op = func(i *encInstr, state *encoderState, sv reflect.Value) {
+				state.update(i)
+				// indirect through info to delay evaluation for recursive structs
+				enc := info.encoder.Load().(*encEngine)
+				state.enc.encodeStruct(state.b, enc, sv)
+			}
+		case reflect.Interface:
+			op = func(i *encInstr, state *encoderState, iv reflect.Value) {
+				if !state.sendZero && (!iv.IsValid() || iv.IsNil()) {
+					return
+				}
+				state.update(i)
+				state.enc.encodeInterface(state.b, iv)
+			}
+		}
+	}
+	if op == nil {
+		errorf("can't happen: encode type %s", rt)
+	}
+	return &op, indir
+}
+
+// gobEncodeOpFor returns the op for a type that is known to implement GobEncoder.
+func gobEncodeOpFor(ut *userTypeInfo) (*encOp, int) {
+	rt := ut.user
+	if ut.encIndir == -1 {
+		rt = reflect.PtrTo(rt)
+	} else if ut.encIndir > 0 {
+		for i := int8(0); i < ut.encIndir; i++ {
+			rt = rt.Elem()
+		}
+	}
+	var op encOp
+	op = func(i *encInstr, state *encoderState, v reflect.Value) {
+		if ut.encIndir == -1 {
+			// Need to climb up one level to turn value into pointer.
+			if !v.CanAddr() {
+				errorf("unaddressable value of type %s", rt)
+			}
+			v = v.Addr()
+		}
+		if !state.sendZero && isZero(v) {
+			return
+		}
+		state.update(i)
+		state.enc.encodeGobEncoder(state.b, ut, v)
+	}
+	return &op, int(ut.encIndir) // encIndir: op will get called with p == address of receiver.
+}
+
+// compileEnc returns the engine to compile the type.
+func compileEnc(ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
+	srt := ut.base
+	engine := new(encEngine)
+	seen := make(map[reflect.Type]*encOp)
+	rt := ut.base
+	if ut.externalEnc != 0 {
+		rt = ut.user
+	}
+	if ut.externalEnc == 0 && srt.Kind() == reflect.Struct {
+		for fieldNum, wireFieldNum := 0, 0; fieldNum < srt.NumField(); fieldNum++ {
+			f := srt.Field(fieldNum)
+			if !isSent(&f) {
+				continue
+			}
+			op, indir := encOpFor(f.Type, seen, building)
+			engine.instr = append(engine.instr, encInstr{*op, wireFieldNum, f.Index, indir})
+			wireFieldNum++
+		}
+		if srt.NumField() > 0 && len(engine.instr) == 0 {
+			errorf("type %s has no exported fields", rt)
+		}
+		engine.instr = append(engine.instr, encInstr{encStructTerminator, 0, nil, 0})
+	} else {
+		engine.instr = make([]encInstr, 1)
+		op, indir := encOpFor(rt, seen, building)
+		engine.instr[0] = encInstr{*op, singletonField, nil, indir}
+	}
+	return engine
+}
+
+// getEncEngine returns the engine to compile the type.
+func getEncEngine(ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
+	info, err := getTypeInfo(ut)
+	if err != nil {
+		error_(err)
+	}
+	enc, ok := info.encoder.Load().(*encEngine)
+	if !ok {
+		enc = buildEncEngine(info, ut, building)
+	}
+	return enc
+}
+
+func buildEncEngine(info *typeInfo, ut *userTypeInfo, building map[*typeInfo]bool) *encEngine {
+	// Check for recursive types.
+	if building != nil && building[info] {
+		return nil
+	}
+	info.encInit.Lock()
+	defer info.encInit.Unlock()
+	enc, ok := info.encoder.Load().(*encEngine)
+	if !ok {
+		if building == nil {
+			building = make(map[*typeInfo]bool)
+		}
+		building[info] = true
+		enc = compileEnc(ut, building)
+		info.encoder.Store(enc)
+	}
+	return enc
+}
+
+func (enc *Encoder) encode(b *encBuffer, value reflect.Value, ut *userTypeInfo) {
+	defer catchError(&enc.err)
+	engine := getEncEngine(ut, nil)
+	indir := ut.indir
+	if ut.externalEnc != 0 {
+		indir = int(ut.encIndir)
+	}
+	for i := 0; i < indir; i++ {
+		value = reflect.Indirect(value)
+	}
+	if ut.externalEnc == 0 && value.Type().Kind() == reflect.Struct {
+		enc.encodeStruct(b, engine, value)
+	} else {
+		enc.encodeSingle(b, engine, value)
+	}
+}