// 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 decgen.go -output dec_helpers.go
package gob
import (
"encoding"
"errors"
"io"
"math"
"math/bits"
"reflect"
)
var (
errBadUint = errors.New("gob: encoded unsigned integer out of range")
errBadType = errors.New("gob: unknown type id or corrupted data")
errRange = errors.New("gob: bad data: field numbers out of bounds")
)
type decHelper func(state *decoderState, v reflect.Value, length int, ovfl error) bool
// decoderState is the execution state of an instance of the decoder. A new state
// is created for nested objects.
type decoderState struct {
dec *Decoder
// The buffer is stored with an extra indirection because it may be replaced
// if we load a type during decode (when reading an interface value).
b *decBuffer
fieldnum int // the last field number read.
next *decoderState // for free list
}
// decBuffer is an extremely simple, fast implementation of a read-only byte buffer.
// It is initialized by calling Size and then copying the data into the slice returned by Bytes().
type decBuffer struct {
data []byte
offset int // Read offset.
}
func (d *decBuffer) Read(p []byte) (int, error) {
n := copy(p, d.data[d.offset:])
if n == 0 && len(p) != 0 {
return 0, io.EOF
}
d.offset += n
return n, nil
}
func (d *decBuffer) Drop(n int) {
if n > d.Len() {
panic("drop")
}
d.offset += n
}
// Size grows the buffer to exactly n bytes, so d.Bytes() will
// return a slice of length n. Existing data is first discarded.
func (d *decBuffer) Size(n int) {
d.Reset()
if cap(d.data) < n {
d.data = make([]byte, n)
} else {
d.data = d.data[0:n]
}
}
func (d *decBuffer) ReadByte() (byte, error) {
if d.offset >= len(d.data) {
return 0, io.EOF
}
c := d.data[d.offset]
d.offset++
return c, nil
}
func (d *decBuffer) Len() int {
return len(d.data) - d.offset
}
func (d *decBuffer) Bytes() []byte {
return d.data[d.offset:]
}
func (d *decBuffer) Reset() {
d.data = d.data[0:0]
d.offset = 0
}
// We pass the bytes.Buffer separately for easier testing of the infrastructure
// without requiring a full Decoder.
func (dec *Decoder) newDecoderState(buf *decBuffer) *decoderState {
d := dec.freeList
if d == nil {
d = new(decoderState)
d.dec = dec
} else {
dec.freeList = d.next
}
d.b = buf
return d
}
func (dec *Decoder) freeDecoderState(d *decoderState) {
d.next = dec.freeList
dec.freeList = d
}
func overflow(name string) error {
return errors.New(`value for "` + name + `" out of range`)
}
// decodeUintReader reads an encoded unsigned integer from an io.Reader.
// Used only by the Decoder to read the message length.
func decodeUintReader(r io.Reader, buf []byte) (x uint64, width int, err error) {
width = 1
n, err := io.ReadFull(r, buf[0:width])
if n == 0 {
return
}
b := buf[0]
if b <= 0x7f {
return uint64(b), width, nil
}
n = -int(int8(b))
if n > uint64Size {
err = errBadUint
return
}
width, err = io.ReadFull(r, buf[0:n])
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return
}
// Could check that the high byte is zero but it's not worth it.
for _, b := range buf[0:width] {
x = x<<8 | uint64(b)
}
width++ // +1 for length byte
return
}
// decodeUint reads an encoded unsigned integer from state.r.
// Does not check for overflow.
func (state *decoderState) decodeUint() (x uint64) {
b, err := state.b.ReadByte()
if err != nil {
error_(err)
}
if b <= 0x7f {
return uint64(b)
}
n := -int(int8(b))
if n > uint64Size {
error_(errBadUint)
}
buf := state.b.Bytes()
if len(buf) < n {
errorf("invalid uint data length %d: exceeds input size %d", n, len(buf))
}
// Don't need to check error; it's safe to loop regardless.
// Could check that the high byte is zero but it's not worth it.
for _, b := range buf[0:n] {
x = x<<8 | uint64(b)
}
state.b.Drop(n)
return x
}
// decodeInt reads an encoded signed integer from state.r.
// Does not check for overflow.
func (state *decoderState) decodeInt() int64 {
x := state.decodeUint()
if x&1 != 0 {
return ^int64(x >> 1)
}
return int64(x >> 1)
}
// getLength decodes the next uint and makes sure it is a possible
// size for a data item that follows, which means it must fit in a
// non-negative int and fit in the buffer.
func (state *decoderState) getLength() (int, bool) {
n := int(state.decodeUint())
if n < 0 || state.b.Len() < n || tooBig <= n {
return 0, false
}
return n, true
}
// decOp is the signature of a decoding operator for a given type.
type decOp func(i *decInstr, state *decoderState, v reflect.Value)
// The 'instructions' of the decoding machine
type decInstr struct {
op decOp
field int // field number of the wire type
index []int // field access indices for destination type
ovfl error // error message for overflow/underflow (for arrays, of the elements)
}
// ignoreUint discards a uint value with no destination.
func ignoreUint(i *decInstr, state *decoderState, v reflect.Value) {
state.decodeUint()
}
// ignoreTwoUints discards a uint value with no destination. It's used to skip
// complex values.
func ignoreTwoUints(i *decInstr, state *decoderState, v reflect.Value) {
state.decodeUint()
state.decodeUint()
}
// Since the encoder writes no zeros, if we arrive at a decoder we have
// a value to extract and store. The field number has already been read
// (it's how we knew to call this decoder).
// Each decoder is responsible for handling any indirections associated
// with the data structure. If any pointer so reached is nil, allocation must
// be done.
// decAlloc takes a value and returns a settable value that can
// be assigned to. If the value is a pointer, decAlloc guarantees it points to storage.
// The callers to the individual decoders are expected to have used decAlloc.
// The individual decoders don't need to it.
func decAlloc(v reflect.Value) reflect.Value {
for v.Kind() == reflect.Ptr {
if v.IsNil() {
v.Set(reflect.New(v.Type().Elem()))
}
v = v.Elem()
}
return v
}
// decBool decodes a uint and stores it as a boolean in value.
func decBool(i *decInstr, state *decoderState, value reflect.Value) {
value.SetBool(state.decodeUint() != 0)
}
// decInt8 decodes an integer and stores it as an int8 in value.
func decInt8(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeInt()
if v < math.MinInt8 || math.MaxInt8 < v {
error_(i.ovfl)
}
value.SetInt(v)
}
// decUint8 decodes an unsigned integer and stores it as a uint8 in value.
func decUint8(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeUint()
if math.MaxUint8 < v {
error_(i.ovfl)
}
value.SetUint(v)
}
// decInt16 decodes an integer and stores it as an int16 in value.
func decInt16(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeInt()
if v < math.MinInt16 || math.MaxInt16 < v {
error_(i.ovfl)
}
value.SetInt(v)
}
// decUint16 decodes an unsigned integer and stores it as a uint16 in value.
func decUint16(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeUint()
if math.MaxUint16 < v {
error_(i.ovfl)
}
value.SetUint(v)
}
// decInt32 decodes an integer and stores it as an int32 in value.
func decInt32(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeInt()
if v < math.MinInt32 || math.MaxInt32 < v {
error_(i.ovfl)
}
value.SetInt(v)
}
// decUint32 decodes an unsigned integer and stores it as a uint32 in value.
func decUint32(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeUint()
if math.MaxUint32 < v {
error_(i.ovfl)
}
value.SetUint(v)
}
// decInt64 decodes an integer and stores it as an int64 in value.
func decInt64(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeInt()
value.SetInt(v)
}
// decUint64 decodes an unsigned integer and stores it as a uint64 in value.
func decUint64(i *decInstr, state *decoderState, value reflect.Value) {
v := state.decodeUint()
value.SetUint(v)
}
// 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
// unswizzling.
func float64FromBits(u uint64) float64 {
v := bits.ReverseBytes64(u)
return math.Float64frombits(v)
}
// float32FromBits decodes an unsigned integer, treats it as a 32-bit floating-point
// number, and returns it. It's a helper function for float32 and complex64.
// It returns a float64 because that's what reflection needs, but its return
// value is known to be accurately representable in a float32.
func float32FromBits(u uint64, ovfl error) float64 {
v := float64FromBits(u)
av := v
if av < 0 {
av = -av
}
// +Inf is OK in both 32- and 64-bit floats. Underflow is always OK.
if math.MaxFloat32 < av && av <= math.MaxFloat64 {
error_(ovfl)
}
return v
}
// decFloat32 decodes an unsigned integer, treats it as a 32-bit floating-point
// number, and stores it in value.
func decFloat32(i *decInstr, state *decoderState, value reflect.Value) {
value.SetFloat(float32FromBits(state.decodeUint(), i.ovfl))
}
// decFloat64 decodes an unsigned integer, treats it as a 64-bit floating-point
// number, and stores it in value.
func decFloat64(i *decInstr, state *decoderState, value reflect.Value) {
value.SetFloat(float64FromBits(state.decodeUint()))
}
// decComplex64 decodes a pair of unsigned integers, treats them as a
// pair of floating point numbers, and stores them as a complex64 in value.
// The real part comes first.
func decComplex64(i *decInstr, state *decoderState, value reflect.Value) {
real := float32FromBits(state.decodeUint(), i.ovfl)
imag := float32FromBits(state.decodeUint(), i.ovfl)
value.SetComplex(complex(real, imag))
}
// decComplex128 decodes a pair of unsigned integers, treats them as a
// pair of floating point numbers, and stores them as a complex128 in value.
// The real part comes first.
func decComplex128(i *decInstr, state *decoderState, value reflect.Value) {
real := float64FromBits(state.decodeUint())
imag := float64FromBits(state.decodeUint())
value.SetComplex(complex(real, imag))
}
// decUint8Slice decodes a byte slice and stores in value a slice header
// describing the data.
// uint8 slices are encoded as an unsigned count followed by the raw bytes.
func decUint8Slice(i *decInstr, state *decoderState, value reflect.Value) {
n, ok := state.getLength()
if !ok {
errorf("bad %s slice length: %d", value.Type(), n)
}
if value.Cap() < n {
value.Set(reflect.MakeSlice(value.Type(), n, n))
} else {
value.Set(value.Slice(0, n))
}
if _, err := state.b.Read(value.Bytes()); err != nil {
errorf("error decoding []byte: %s", err)
}
}
// decString decodes byte array and stores in value a string header
// describing the data.
// Strings are encoded as an unsigned count followed by the raw bytes.
func decString(i *decInstr, state *decoderState, value reflect.Value) {
n, ok := state.getLength()
if !ok {
errorf("bad %s slice length: %d", value.Type(), n)
}
// Read the data.
data := state.b.Bytes()
if len(data) < n {
errorf("invalid string length %d: exceeds input size %d", n, len(data))
}
s := string(data[:n])
state.b.Drop(n)
value.SetString(s)
}
// ignoreUint8Array skips over the data for a byte slice value with no destination.
func ignoreUint8Array(i *decInstr, state *decoderState, value reflect.Value) {
n, ok := state.getLength()
if !ok {
errorf("slice length too large")
}
bn := state.b.Len()
if bn < n {
errorf("invalid slice length %d: exceeds input size %d", n, bn)
}
state.b.Drop(n)
}
// Execution engine
// The encoder engine is an array of instructions indexed by field number of the incoming
// decoder. It is executed with random access according to field number.
type decEngine struct {
instr []decInstr
numInstr int // the number of active instructions
}
// decodeSingle decodes a top-level value that is not a struct and stores it in value.
// Such values are preceded by a zero, making them have the memory layout of a
// struct field (although with an illegal field number).
func (dec *Decoder) decodeSingle(engine *decEngine, value reflect.Value) {
state := dec.newDecoderState(&dec.buf)
defer dec.freeDecoderState(state)
state.fieldnum = singletonField
if state.decodeUint() != 0 {
errorf("decode: corrupted data: non-zero delta for singleton")
}
instr := &engine.instr[singletonField]
instr.op(instr, state, value)
}
// decodeStruct decodes a top-level struct and stores it in value.
// Indir is for the value, not the type. At the time of the call it may
// differ from ut.indir, which was computed when the engine was built.
// This state cannot arise for decodeSingle, which is called directly
// from the user's value, not from the innards of an engine.
func (dec *Decoder) decodeStruct(engine *decEngine, value reflect.Value) {
state := dec.newDecoderState(&dec.buf)
defer dec.freeDecoderState(state)
state.fieldnum = -1
for state.b.Len() > 0 {
delta := int(state.decodeUint())
if delta < 0 {
errorf("decode: corrupted data: negative delta")
}
if delta == 0 { // struct terminator is zero delta fieldnum
break
}
fieldnum := state.fieldnum + delta
if fieldnum >= len(engine.instr) {
error_(errRange)
break
}
instr := &engine.instr[fieldnum]
var field reflect.Value
if instr.index != nil {
// Otherwise the field is unknown to us and instr.op is an ignore op.
field = value.FieldByIndex(instr.index)
if field.Kind() == reflect.Ptr {
field = decAlloc(field)
}
}
instr.op(instr, state, field)
state.fieldnum = fieldnum
}
}
var noValue reflect.Value
// ignoreStruct discards the data for a struct with no destination.
func (dec *Decoder) ignoreStruct(engine *decEngine) {
state := dec.newDecoderState(&dec.buf)
defer dec.freeDecoderState(state)
state.fieldnum = -1
for state.b.Len() > 0 {
delta := int(state.decodeUint())
if delta < 0 {
errorf("ignore decode: corrupted data: negative delta")
}
if delta == 0 { // struct terminator is zero delta fieldnum
break
}
fieldnum := state.fieldnum + delta
if fieldnum >= len(engine.instr) {
error_(errRange)
}
instr := &engine.instr[fieldnum]
instr.op(instr, state, noValue)
state.fieldnum = fieldnum
}
}
// ignoreSingle discards the data for a top-level non-struct value with no
// destination. It's used when calling Decode with a nil value.
func (dec *Decoder) ignoreSingle(engine *decEngine) {
state := dec.newDecoderState(&dec.buf)
defer dec.freeDecoderState(state)
state.fieldnum = singletonField
delta := int(state.decodeUint())
if delta != 0 {
errorf("decode: corrupted data: non-zero delta for singleton")
}
instr := &engine.instr[singletonField]
instr.op(instr, state, noValue)
}
// decodeArrayHelper does the work for decoding arrays and slices.
func (dec *Decoder) decodeArrayHelper(state *decoderState, value reflect.Value, elemOp decOp, length int, ovfl error, helper decHelper) {
if helper != nil && helper(state, value, length, ovfl) {
return
}
instr := &decInstr{elemOp, 0, nil, ovfl}
isPtr := value.Type().Elem().Kind() == reflect.Ptr
for i := 0; i < length; i++ {
if state.b.Len() == 0 {
errorf("decoding array or slice: length exceeds input size (%d elements)", length)
}
v := value.Index(i)
if isPtr {
v = decAlloc(v)
}
elemOp(instr, state, v)
}
}
// decodeArray decodes an array and stores it in value.
// The length is an unsigned integer preceding the elements. Even though the length is redundant
// (it's part of the type), it's a useful check and is included in the encoding.
func (dec *Decoder) decodeArray(state *decoderState, value reflect.Value, elemOp decOp, length int, ovfl error, helper decHelper) {
if n := state.decodeUint(); n != uint64(length) {
errorf("length mismatch in decodeArray")
}
dec.decodeArrayHelper(state, value, elemOp, length, ovfl, helper)
}
// decodeIntoValue is a helper for map decoding.
func decodeIntoValue(state *decoderState, op decOp, isPtr bool, value reflect.Value, instr *decInstr) reflect.Value {
v := value
if isPtr {
v = decAlloc(value)
}
op(instr, state, v)
return value
}
// decodeMap decodes a map and stores it in value.
// Maps are encoded as a length followed by key:value pairs.
// Because the internals of maps are not visible to us, we must
// use reflection rather than pointer magic.
func (dec *Decoder) decodeMap(mtyp reflect.Type, state *decoderState, value reflect.Value, keyOp, elemOp decOp, ovfl error) {
n := int(state.decodeUint())
if value.IsNil() {
value.Set(reflect.MakeMapWithSize(mtyp, n))
}
keyIsPtr := mtyp.Key().Kind() == reflect.Ptr
elemIsPtr := mtyp.Elem().Kind() == reflect.Ptr
keyInstr := &decInstr{keyOp, 0, nil, ovfl}
elemInstr := &decInstr{elemOp, 0, nil, ovfl}
keyP := reflect.New(mtyp.Key())
keyZ := reflect.Zero(mtyp.Key())
elemP := reflect.New(mtyp.Elem())
elemZ := reflect.Zero(mtyp.Elem())
for i := 0; i < n; i++ {
key := decodeIntoValue(state, keyOp, keyIsPtr, keyP.Elem(), keyInstr)
elem := decodeIntoValue(state, elemOp, elemIsPtr, elemP.Elem(), elemInstr)
value.SetMapIndex(key, elem)
keyP.Elem().Set(keyZ)
elemP.Elem().Set(elemZ)
}
}
// ignoreArrayHelper does the work for discarding arrays and slices.
func (dec *Decoder) ignoreArrayHelper(state *decoderState, elemOp decOp, length int) {
instr := &decInstr{elemOp, 0, nil, errors.New("no error")}
for i := 0; i < length; i++ {
if state.b.Len() == 0 {
errorf("decoding array or slice: length exceeds input size (%d elements)", length)
}
elemOp(instr, state, noValue)
}
}
// ignoreArray discards the data for an array value with no destination.
func (dec *Decoder) ignoreArray(state *decoderState, elemOp decOp, length int) {
if n := state.decodeUint(); n != uint64(length) {
errorf("length mismatch in ignoreArray")
}
dec.ignoreArrayHelper(state, elemOp, length)
}
// ignoreMap discards the data for a map value with no destination.
func (dec *Decoder) ignoreMap(state *decoderState, keyOp, elemOp decOp) {
n := int(state.decodeUint())
keyInstr := &decInstr{keyOp, 0, nil, errors.New("no error")}
elemInstr := &decInstr{elemOp, 0, nil, errors.New("no error")}
for i := 0; i < n; i++ {
keyOp(keyInstr, state, noValue)
elemOp(elemInstr, state, noValue)
}
}
// decodeSlice decodes a slice and stores it in value.
// Slices are encoded as an unsigned length followed by the elements.
func (dec *Decoder) decodeSlice(state *decoderState, value reflect.Value, elemOp decOp, ovfl error, helper decHelper) {
u := state.decodeUint()
typ := value.Type()
size := uint64(typ.Elem().Size())
nBytes := u * size
n := int(u)
// Take care with overflow in this calculation.
if n < 0 || uint64(n) != u || nBytes > tooBig || (size > 0 && nBytes/size != u) {
// We don't check n against buffer length here because if it's a slice
// of interfaces, there will be buffer reloads.
errorf("%s slice too big: %d elements of %d bytes", typ.Elem(), u, size)
}
if value.Cap() < n {
value.Set(reflect.MakeSlice(typ, n, n))
} else {
value.Set(value.Slice(0, n))
}
dec.decodeArrayHelper(state, value, elemOp, n, ovfl, helper)
}
// ignoreSlice skips over the data for a slice value with no destination.
func (dec *Decoder) ignoreSlice(state *decoderState, elemOp decOp) {
dec.ignoreArrayHelper(state, elemOp, int(state.decodeUint()))
}
// decodeInterface decodes an interface value and stores it in value.
// Interfaces are encoded as the name of a concrete type followed by a value.
// If the name is empty, the value is nil and no value is sent.
func (dec *Decoder) decodeInterface(ityp reflect.Type, state *decoderState, value reflect.Value) {
// Read the name of the concrete type.
nr := state.decodeUint()
if nr > 1<<31 { // zero is permissible for anonymous types
errorf("invalid type name length %d", nr)
}
if nr > uint64(state.b.Len()) {
errorf("invalid type name length %d: exceeds input size", nr)
}
n := int(nr)
name := state.b.Bytes()[:n]
state.b.Drop(n)
// Allocate the destination interface value.
if len(name) == 0 {
// Copy the nil interface value to the target.
value.Set(reflect.Zero(value.Type()))
return
}
if len(name) > 1024 {
errorf("name too long (%d bytes): %.20q...", len(name), name)
}
// The concrete type must be registered.
typi, ok := nameToConcreteType.Load(string(name))
if !ok {
errorf("name not registered for interface: %q", name)
}
typ := typi.(reflect.Type)
// Read the type id of the concrete value.
concreteId := dec.decodeTypeSequence(true)
if concreteId < 0 {
error_(dec.err)
}
// Byte count of value is next; we don't care what it is (it's there
// in case we want to ignore the value by skipping it completely).
state.decodeUint()
// Read the concrete value.
v := allocValue(typ)
dec.decodeValue(concreteId, v)
if dec.err != nil {
error_(dec.err)
}
// Assign the concrete value to the interface.
// Tread carefully; it might not satisfy the interface.
if !typ.AssignableTo(ityp) {
errorf("%s is not assignable to type %s", typ, ityp)
}
// Copy the interface value to the target.
value.Set(v)
}
// ignoreInterface discards the data for an interface value with no destination.
func (dec *Decoder) ignoreInterface(state *decoderState) {
// Read the name of the concrete type.
n, ok := state.getLength()
if !ok {
errorf("bad interface encoding: name too large for buffer")
}
bn := state.b.Len()
if bn < n {
errorf("invalid interface value length %d: exceeds input size %d", n, bn)
}
state.b.Drop(n)
id := dec.decodeTypeSequence(true)
if id < 0 {
error_(dec.err)
}
// At this point, the decoder buffer contains a delimited value. Just toss it.
n, ok = state.getLength()
if !ok {
errorf("bad interface encoding: data length too large for buffer")
}
state.b.Drop(n)
}
// decodeGobDecoder decodes something implementing the GobDecoder interface.
// The data is encoded as a byte slice.
func (dec *Decoder) decodeGobDecoder(ut *userTypeInfo, state *decoderState, value reflect.Value) {
// Read the bytes for the value.
n, ok := state.getLength()
if !ok {
errorf("GobDecoder: length too large for buffer")
}
b := state.b.Bytes()
if len(b) < n {
errorf("GobDecoder: invalid data length %d: exceeds input size %d", n, len(b))
}
b = b[:n]
state.b.Drop(n)
var err error
// We know it's one of these.
switch ut.externalDec {
case xGob:
err = value.Interface().(GobDecoder).GobDecode(b)
case xBinary:
err = value.Interface().(encoding.BinaryUnmarshaler).UnmarshalBinary(b)
case xText:
err = value.Interface().(encoding.TextUnmarshaler).UnmarshalText(b)
}
if err != nil {
error_(err)
}
}
// ignoreGobDecoder discards the data for a GobDecoder value with no destination.
func (dec *Decoder) ignoreGobDecoder(state *decoderState) {
// Read the bytes for the value.
n, ok := state.getLength()
if !ok {
errorf("GobDecoder: length too large for buffer")
}
bn := state.b.Len()
if bn < n {
errorf("GobDecoder: invalid data length %d: exceeds input size %d", n, bn)
}
state.b.Drop(n)
}
// Index by Go types.
var decOpTable = [...]decOp{
reflect.Bool: decBool,
reflect.Int8: decInt8,
reflect.Int16: decInt16,
reflect.Int32: decInt32,
reflect.Int64: decInt64,
reflect.Uint8: decUint8,
reflect.Uint16: decUint16,
reflect.Uint32: decUint32,
reflect.Uint64: decUint64,
reflect.Float32: decFloat32,
reflect.Float64: decFloat64,
reflect.Complex64: decComplex64,
reflect.Complex128: decComplex128,
reflect.String: decString,
}
// Indexed by gob types. tComplex will be added during type.init().
var decIgnoreOpMap = map[typeId]decOp{
tBool: ignoreUint,
tInt: ignoreUint,
tUint: ignoreUint,
tFloat: ignoreUint,
tBytes: ignoreUint8Array,
tString: ignoreUint8Array,
tComplex: ignoreTwoUints,
}
// decOpFor returns the decoding op for the base type under rt and
// the indirection count to reach it.
func (dec *Decoder) decOpFor(wireId typeId, rt reflect.Type, name string, inProgress map[reflect.Type]*decOp) *decOp {
ut := userType(rt)
// If the type implements GobEncoder, we handle it without further processing.
if ut.externalDec != 0 {
return dec.gobDecodeOpFor(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
}
typ := ut.base
var op decOp
k := typ.Kind()
if int(k) < len(decOpTable) {
op = decOpTable[k]
}
if op == nil {
inProgress[rt] = &op
// Special cases
switch t := typ; t.Kind() {
case reflect.Array:
name = "element of " + name
elemId := dec.wireType[wireId].ArrayT.Elem
elemOp := dec.decOpFor(elemId, t.Elem(), name, inProgress)
ovfl := overflow(name)
helper := decArrayHelper[t.Elem().Kind()]
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.decodeArray(state, value, *elemOp, t.Len(), ovfl, helper)
}
case reflect.Map:
keyId := dec.wireType[wireId].MapT.Key
elemId := dec.wireType[wireId].MapT.Elem
keyOp := dec.decOpFor(keyId, t.Key(), "key of "+name, inProgress)
elemOp := dec.decOpFor(elemId, t.Elem(), "element of "+name, inProgress)
ovfl := overflow(name)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.decodeMap(t, state, value, *keyOp, *elemOp, ovfl)
}
case reflect.Slice:
name = "element of " + name
if t.Elem().Kind() == reflect.Uint8 {
op = decUint8Slice
break
}
var elemId typeId
if tt, ok := builtinIdToType[wireId]; ok {
elemId = tt.(*sliceType).Elem
} else {
elemId = dec.wireType[wireId].SliceT.Elem
}
elemOp := dec.decOpFor(elemId, t.Elem(), name, inProgress)
ovfl := overflow(name)
helper := decSliceHelper[t.Elem().Kind()]
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.decodeSlice(state, value, *elemOp, ovfl, helper)
}
case reflect.Struct:
// Generate a closure that calls out to the engine for the nested type.
ut := userType(typ)
enginePtr, err := dec.getDecEnginePtr(wireId, ut)
if err != nil {
error_(err)
}
op = func(i *decInstr, state *decoderState, value reflect.Value) {
// indirect through enginePtr to delay evaluation for recursive structs.
dec.decodeStruct(*enginePtr, value)
}
case reflect.Interface:
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.decodeInterface(t, state, value)
}
}
}
if op == nil {
errorf("decode can't handle type %s", rt)
}
return &op
}
// decIgnoreOpFor returns the decoding op for a field that has no destination.
func (dec *Decoder) decIgnoreOpFor(wireId typeId, inProgress map[typeId]*decOp) *decOp {
// 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[wireId]; opPtr != nil {
return opPtr
}
op, ok := decIgnoreOpMap[wireId]
if !ok {
inProgress[wireId] = &op
if wireId == tInterface {
// Special case because it's a method: the ignored item might
// define types and we need to record their state in the decoder.
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreInterface(state)
}
return &op
}
// Special cases
wire := dec.wireType[wireId]
switch {
case wire == nil:
errorf("bad data: undefined type %s", wireId.string())
case wire.ArrayT != nil:
elemId := wire.ArrayT.Elem
elemOp := dec.decIgnoreOpFor(elemId, inProgress)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreArray(state, *elemOp, wire.ArrayT.Len)
}
case wire.MapT != nil:
keyId := dec.wireType[wireId].MapT.Key
elemId := dec.wireType[wireId].MapT.Elem
keyOp := dec.decIgnoreOpFor(keyId, inProgress)
elemOp := dec.decIgnoreOpFor(elemId, inProgress)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreMap(state, *keyOp, *elemOp)
}
case wire.SliceT != nil:
elemId := wire.SliceT.Elem
elemOp := dec.decIgnoreOpFor(elemId, inProgress)
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreSlice(state, *elemOp)
}
case wire.StructT != nil:
// Generate a closure that calls out to the engine for the nested type.
enginePtr, err := dec.getIgnoreEnginePtr(wireId)
if err != nil {
error_(err)
}
op = func(i *decInstr, state *decoderState, value reflect.Value) {
// indirect through enginePtr to delay evaluation for recursive structs
state.dec.ignoreStruct(*enginePtr)
}
case wire.GobEncoderT != nil, wire.BinaryMarshalerT != nil, wire.TextMarshalerT != nil:
op = func(i *decInstr, state *decoderState, value reflect.Value) {
state.dec.ignoreGobDecoder(state)
}
}
}
if op == nil {
errorf("bad data: ignore can't handle type %s", wireId.string())
}
return &op
}
// gobDecodeOpFor returns the op for a type that is known to implement
// GobDecoder.
func (dec *Decoder) gobDecodeOpFor(ut *userTypeInfo) *decOp {
rcvrType := ut.user
if ut.decIndir == -1 {
rcvrType = reflect.PtrTo(rcvrType)
} else if ut.decIndir > 0 {
for i := int8(0); i < ut.decIndir; i++ {
rcvrType = rcvrType.Elem()
}
}
var op decOp
op = func(i *decInstr, state *decoderState, value reflect.Value) {
// We now have the base type. We need its address if the receiver is a pointer.
if value.Kind() != reflect.Ptr && rcvrType.Kind() == reflect.Ptr {
value = value.Addr()
}
state.dec.decodeGobDecoder(ut, state, value)
}
return &op
}
// compatibleType asks: Are these two gob Types compatible?
// Answers the question for basic types, arrays, maps and slices, plus
// GobEncoder/Decoder pairs.
// Structs are considered ok; fields will be checked later.
func (dec *Decoder) compatibleType(fr reflect.Type, fw typeId, inProgress map[reflect.Type]typeId) bool {
if rhs, ok := inProgress[fr]; ok {
return rhs == fw
}
inProgress[fr] = fw
ut := userType(fr)
wire, ok := dec.wireType[fw]
// If wire was encoded with an encoding method, fr must have that method.
// And if not, it must not.
// At most one of the booleans in ut is set.
// We could possibly relax this constraint in the future in order to
// choose the decoding method using the data in the wireType.
// The parentheses look odd but are correct.
if (ut.externalDec == xGob) != (ok && wire.GobEncoderT != nil) ||
(ut.externalDec == xBinary) != (ok && wire.BinaryMarshalerT != nil) ||
(ut.externalDec == xText) != (ok && wire.TextMarshalerT != nil) {
return false
}
if ut.externalDec != 0 { // This test trumps all others.
return true
}
switch t := ut.base; t.Kind() {
default:
// chan, etc: cannot handle.
return false
case reflect.Bool:
return fw == tBool
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return fw == tInt
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return fw == tUint
case reflect.Float32, reflect.Float64:
return fw == tFloat
case reflect.Complex64, reflect.Complex128:
return fw == tComplex
case reflect.String:
return fw == tString
case reflect.Interface:
return fw == tInterface
case reflect.Array:
if !ok || wire.ArrayT == nil {
return false
}
array := wire.ArrayT
return t.Len() == array.Len && dec.compatibleType(t.Elem(), array.Elem, inProgress)
case reflect.Map:
if !ok || wire.MapT == nil {
return false
}
MapType := wire.MapT
return dec.compatibleType(t.Key(), MapType.Key, inProgress) && dec.compatibleType(t.Elem(), MapType.Elem, inProgress)
case reflect.Slice:
// Is it an array of bytes?
if t.Elem().Kind() == reflect.Uint8 {
return fw == tBytes
}
// Extract and compare element types.
var sw *sliceType
if tt, ok := builtinIdToType[fw]; ok {
sw, _ = tt.(*sliceType)
} else if wire != nil {
sw = wire.SliceT
}
elem := userType(t.Elem()).base
return sw != nil && dec.compatibleType(elem, sw.Elem, inProgress)
case reflect.Struct:
return true
}
}
// typeString returns a human-readable description of the type identified by remoteId.
func (dec *Decoder) typeString(remoteId typeId) string {
typeLock.Lock()
defer typeLock.Unlock()
if t := idToType[remoteId]; t != nil {
// globally known type.
return t.string()
}
return dec.wireType[remoteId].string()
}
// compileSingle compiles the decoder engine for a non-struct top-level value, including
// GobDecoders.
func (dec *Decoder) compileSingle(remoteId typeId, ut *userTypeInfo) (engine *decEngine, err error) {
rt := ut.user
engine = new(decEngine)
engine.instr = make([]decInstr, 1) // one item
name := rt.String() // best we can do
if !dec.compatibleType(rt, remoteId, make(map[reflect.Type]typeId)) {
remoteType := dec.typeString(remoteId)
// Common confusing case: local interface type, remote concrete type.
if ut.base.Kind() == reflect.Interface && remoteId != tInterface {
return nil, errors.New("gob: local interface type " + name + " can only be decoded from remote interface type; received concrete type " + remoteType)
}
return nil, errors.New("gob: decoding into local type " + name + ", received remote type " + remoteType)
}
op := dec.decOpFor(remoteId, rt, name, make(map[reflect.Type]*decOp))
ovfl := errors.New(`value for "` + name + `" out of range`)
engine.instr[singletonField] = decInstr{*op, singletonField, nil, ovfl}
engine.numInstr = 1
return
}
// compileIgnoreSingle compiles the decoder engine for a non-struct top-level value that will be discarded.
func (dec *Decoder) compileIgnoreSingle(remoteId typeId) *decEngine {
engine := new(decEngine)
engine.instr = make([]decInstr, 1) // one item
op := dec.decIgnoreOpFor(remoteId, make(map[typeId]*decOp))
ovfl := overflow(dec.typeString(remoteId))
engine.instr[0] = decInstr{*op, 0, nil, ovfl}
engine.numInstr = 1
return engine
}
// compileDec compiles the decoder engine for a value. If the value is not a struct,
// it calls out to compileSingle.
func (dec *Decoder) compileDec(remoteId typeId, ut *userTypeInfo) (engine *decEngine, err error) {
defer catchError(&err)
rt := ut.base
srt := rt
if srt.Kind() != reflect.Struct || ut.externalDec != 0 {
return dec.compileSingle(remoteId, ut)
}
var wireStruct *structType
// Builtin types can come from global pool; the rest must be defined by the decoder.
// Also we know we're decoding a struct now, so the client must have sent one.
if t, ok := builtinIdToType[remoteId]; ok {
wireStruct, _ = t.(*structType)
} else {
wire := dec.wireType[remoteId]
if wire == nil {
error_(errBadType)
}
wireStruct = wire.StructT
}
if wireStruct == nil {
errorf("type mismatch in decoder: want struct type %s; got non-struct", rt)
}
engine = new(decEngine)
engine.instr = make([]decInstr, len(wireStruct.Field))
seen := make(map[reflect.Type]*decOp)
// Loop over the fields of the wire type.
for fieldnum := 0; fieldnum < len(wireStruct.Field); fieldnum++ {
wireField := wireStruct.Field[fieldnum]
if wireField.Name == "" {
errorf("empty name for remote field of type %s", wireStruct.Name)
}
ovfl := overflow(wireField.Name)
// Find the field of the local type with the same name.
localField, present := srt.FieldByName(wireField.Name)
// TODO(r): anonymous names
if !present || !isExported(wireField.Name) {
op := dec.decIgnoreOpFor(wireField.Id, make(map[typeId]*decOp))
engine.instr[fieldnum] = decInstr{*op, fieldnum, nil, ovfl}
continue
}
if !dec.compatibleType(localField.Type, wireField.Id, make(map[reflect.Type]typeId)) {
errorf("wrong type (%s) for received field %s.%s", localField.Type, wireStruct.Name, wireField.Name)
}
op := dec.decOpFor(wireField.Id, localField.Type, localField.Name, seen)
engine.instr[fieldnum] = decInstr{*op, fieldnum, localField.Index, ovfl}
engine.numInstr++
}
return
}
// getDecEnginePtr returns the engine for the specified type.
func (dec *Decoder) getDecEnginePtr(remoteId typeId, ut *userTypeInfo) (enginePtr **decEngine, err error) {
rt := ut.user
decoderMap, ok := dec.decoderCache[rt]
if !ok {
decoderMap = make(map[typeId]**decEngine)
dec.decoderCache[rt] = decoderMap
}
if enginePtr, ok = decoderMap[remoteId]; !ok {
// To handle recursive types, mark this engine as underway before compiling.
enginePtr = new(*decEngine)
decoderMap[remoteId] = enginePtr
*enginePtr, err = dec.compileDec(remoteId, ut)
if err != nil {
delete(decoderMap, remoteId)
}
}
return
}
// emptyStruct is the type we compile into when ignoring a struct value.
type emptyStruct struct{}
var emptyStructType = reflect.TypeOf(emptyStruct{})
// getIgnoreEnginePtr returns the engine for the specified type when the value is to be discarded.
func (dec *Decoder) getIgnoreEnginePtr(wireId typeId) (enginePtr **decEngine, err error) {
var ok bool
if enginePtr, ok = dec.ignorerCache[wireId]; !ok {
// To handle recursive types, mark this engine as underway before compiling.
enginePtr = new(*decEngine)
dec.ignorerCache[wireId] = enginePtr
wire := dec.wireType[wireId]
if wire != nil && wire.StructT != nil {
*enginePtr, err = dec.compileDec(wireId, userType(emptyStructType))
} else {
*enginePtr = dec.compileIgnoreSingle(wireId)
}
if err != nil {
delete(dec.ignorerCache, wireId)
}
}
return
}
// decodeValue decodes the data stream representing a value and stores it in value.
func (dec *Decoder) decodeValue(wireId typeId, value reflect.Value) {
defer catchError(&dec.err)
// If the value is nil, it means we should just ignore this item.
if !value.IsValid() {
dec.decodeIgnoredValue(wireId)
return
}
// Dereference down to the underlying type.
ut := userType(value.Type())
base := ut.base
var enginePtr **decEngine
enginePtr, dec.err = dec.getDecEnginePtr(wireId, ut)
if dec.err != nil {
return
}
value = decAlloc(value)
engine := *enginePtr
if st := base; st.Kind() == reflect.Struct && ut.externalDec == 0 {
wt := dec.wireType[wireId]
if engine.numInstr == 0 && st.NumField() > 0 &&
wt != nil && len(wt.StructT.Field) > 0 {
name := base.Name()
errorf("type mismatch: no fields matched compiling decoder for %s", name)
}
dec.decodeStruct(engine, value)
} else {
dec.decodeSingle(engine, value)
}
}
// decodeIgnoredValue decodes the data stream representing a value of the specified type and discards it.
func (dec *Decoder) decodeIgnoredValue(wireId typeId) {
var enginePtr **decEngine
enginePtr, dec.err = dec.getIgnoreEnginePtr(wireId)
if dec.err != nil {
return
}
wire := dec.wireType[wireId]
if wire != nil && wire.StructT != nil {
dec.ignoreStruct(*enginePtr)
} else {
dec.ignoreSingle(*enginePtr)
}
}
func init() {
var iop, uop decOp
switch reflect.TypeOf(int(0)).Bits() {
case 32:
iop = decInt32
uop = decUint32
case 64:
iop = decInt64
uop = decUint64
default:
panic("gob: unknown size of int/uint")
}
decOpTable[reflect.Int] = iop
decOpTable[reflect.Uint] = uop
// Finally uintptr
switch reflect.TypeOf(uintptr(0)).Bits() {
case 32:
uop = decUint32
case 64:
uop = decUint64
default:
panic("gob: unknown size of uintptr")
}
decOpTable[reflect.Uintptr] = uop
}
// Gob depends on being able to take the address
// of zeroed Values it creates, so use this wrapper instead
// of the standard reflect.Zero.
// Each call allocates once.
func allocValue(t reflect.Type) reflect.Value {
return reflect.New(t).Elem()
}
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