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-rw-r--r--src/encoding/gob/encode.go661
1 files changed, 661 insertions, 0 deletions
diff --git a/src/encoding/gob/encode.go b/src/encoding/gob/encode.go
new file mode 100644
index 0000000000..5d35db20e6
--- /dev/null
+++ b/src/encoding/gob/encode.go
@@ -0,0 +1,661 @@
+// 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"
+ "encoding"
+ "math"
+ "reflect"
+)
+
+const uint64Size = 8
+
+// 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 *bytes.Buffer
+ 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
+}
+
+func (enc *Encoder) newEncoderState(b *bytes.Buffer) *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
+ 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 {
+ err := state.b.WriteByte(uint8(x))
+ if err != nil {
+ error_(err)
+ }
+ return
+ }
+ i := uint64Size
+ for x > 0 {
+ state.buf[i] = uint8(x)
+ x >>= 8
+ i--
+ }
+ state.buf[i] = uint8(i - uint64Size) // = loop count, negated
+ _, err := state.b.Write(state.buf[i : uint64Size+1])
+ if err != nil {
+ error_(err)
+ }
+}
+
+// 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(uint64(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)
+ var v uint64
+ for i := 0; i < 8; i++ {
+ v <<= 8
+ v |= u & 0xFF
+ u >>= 8
+ }
+ return v
+}
+
+// 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 *bytes.Buffer, 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 *bytes.Buffer, 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)
+ }
+ if !valid(field) {
+ continue
+ }
+ instr.op(instr, state, field)
+ }
+}
+
+// encodeArray encodes the array whose 0th element is at p.
+func (enc *Encoder) encodeArray(b *bytes.Buffer, value reflect.Value, op encOp, elemIndir int, length int) {
+ state := enc.newEncoderState(b)
+ defer enc.freeEncoderState(state)
+ state.fieldnum = -1
+ state.sendZero = true
+ state.encodeUint(uint64(length))
+ for i := 0; i < length; i++ {
+ elem := value.Index(i)
+ if elemIndir > 0 {
+ elem = encIndirect(elem, elemIndir)
+ 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 *bytes.Buffer, 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 *bytes.Buffer, 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())
+ registerLock.RLock()
+ name, ok := concreteTypeToName[ut.base]
+ registerLock.RUnlock()
+ if !ok {
+ errorf("type not registered for interface: %s", ut.base)
+ }
+ // Send the name.
+ state.encodeUint(uint64(len(name)))
+ _, err := state.b.WriteString(name)
+ if err != nil {
+ error_(err)
+ }
+ // 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 := new(bytes.Buffer)
+ data.Write(spaceForLength)
+ enc.encode(data, elem, ut)
+ if enc.err != nil {
+ error_(enc.err)
+ }
+ enc.popWriter()
+ enc.writeMessage(b, data)
+ if enc.err != nil {
+ error_(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 *bytes.Buffer, 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) (*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)
+ 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())
+ }
+ case reflect.Array:
+ // True arrays have size in the type.
+ elemOp, elemIndir := encOpFor(t.Elem(), inProgress)
+ op = func(i *encInstr, state *encoderState, array reflect.Value) {
+ state.update(i)
+ state.enc.encodeArray(state.b, array, *elemOp, elemIndir, array.Len())
+ }
+ case reflect.Map:
+ keyOp, keyIndir := encOpFor(t.Key(), inProgress)
+ elemOp, elemIndir := encOpFor(t.Elem(), inProgress)
+ 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))
+ info := mustGetTypeInfo(typ)
+ op = func(i *encInstr, state *encoderState, sv reflect.Value) {
+ state.update(i)
+ // indirect through info to delay evaluation for recursive structs
+ state.enc.encodeStruct(state.b, info.encoder, 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) *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)
+ 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)
+ engine.instr[0] = encInstr{*op, singletonField, nil, indir}
+ }
+ return engine
+}
+
+// getEncEngine returns the engine to compile the type.
+// typeLock must be held (or we're in initialization and guaranteed single-threaded).
+func getEncEngine(ut *userTypeInfo) *encEngine {
+ info, err1 := getTypeInfo(ut)
+ if err1 != nil {
+ error_(err1)
+ }
+ if info.encoder == nil {
+ // Assign the encEngine now, so recursive types work correctly. But...
+ info.encoder = new(encEngine)
+ // ... if we fail to complete building the engine, don't cache the half-built machine.
+ // Doing this here means we won't cache a type that is itself OK but
+ // that contains a nested type that won't compile. The result is consistent
+ // error behavior when Encode is called multiple times on the top-level type.
+ ok := false
+ defer func() {
+ if !ok {
+ info.encoder = nil
+ }
+ }()
+ info.encoder = compileEnc(ut)
+ ok = true
+ }
+ return info.encoder
+}
+
+// lockAndGetEncEngine is a function that locks and compiles.
+// This lets us hold the lock only while compiling, not when encoding.
+func lockAndGetEncEngine(ut *userTypeInfo) *encEngine {
+ typeLock.Lock()
+ defer typeLock.Unlock()
+ return getEncEngine(ut)
+}
+
+func (enc *Encoder) encode(b *bytes.Buffer, value reflect.Value, ut *userTypeInfo) {
+ defer catchError(&enc.err)
+ engine := lockAndGetEncEngine(ut)
+ 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)
+ }
+}
generated by cgit v1.3 (git 2.53.0) at 2026-04-15 09:08:35 +0000