summaryrefslogtreecommitdiff
path: root/src/encoding/gob/decode.go
diff options
context:
space:
mode:
Diffstat (limited to 'src/encoding/gob/decode.go')
-rw-r--r--src/encoding/gob/decode.go1217
1 files changed, 1217 insertions, 0 deletions
diff --git a/src/encoding/gob/decode.go b/src/encoding/gob/decode.go
new file mode 100644
index 000000000..a5bef9314
--- /dev/null
+++ b/src/encoding/gob/decode.go
@@ -0,0 +1,1217 @@
+// 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"
+ "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.
+ buf []byte
+ 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
+ d.buf = make([]byte, uint64Size)
+ } 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)
+ }
+ width, err := state.b.Read(state.buf[0:n])
+ if err != nil {
+ error_(err)
+ }
+ // 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 state.buf[0:width] {
+ x = x<<8 | uint64(b)
+ }
+ 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)
+}
+
+// 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 {
+ var v uint64
+ for i := 0; i < 8; i++ {
+ v <<= 8
+ v |= u & 0xFF
+ u >>= 8
+ }
+ 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) {
+ u := state.decodeUint()
+ n := int(u)
+ if n < 0 || uint64(n) != u {
+ errorf("length of %s exceeds input size (%d bytes)", value.Type(), u)
+ }
+ if n > state.b.Len() {
+ errorf("%s data too long for buffer: %d", value.Type(), n)
+ }
+ if n > tooBig {
+ errorf("byte slice too big: %d", 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) {
+ u := state.decodeUint()
+ n := int(u)
+ if n < 0 || uint64(n) != u || n > state.b.Len() {
+ errorf("length of %s exceeds input size (%d bytes)", value.Type(), u)
+ }
+ if n > state.b.Len() {
+ errorf("%s data too long for buffer: %d", value.Type(), n)
+ }
+ // Read the data.
+ data := make([]byte, n)
+ if _, err := state.b.Read(data); err != nil {
+ errorf("error decoding string: %s", err)
+ }
+ value.SetString(string(data))
+}
+
+// ignoreUint8Array skips over the data for a byte slice value with no destination.
+func ignoreUint8Array(i *decInstr, state *decoderState, value reflect.Value) {
+ b := make([]byte, state.decodeUint())
+ state.b.Read(b)
+}
+
+// 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, ut *userTypeInfo, 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, ut *userTypeInfo, 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(atyp reflect.Type, 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, ovfl error) reflect.Value {
+ instr := &decInstr{op, 0, nil, ovfl}
+ 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) {
+ if value.IsNil() {
+ // Allocate map.
+ value.Set(reflect.MakeMap(mtyp))
+ }
+ n := int(state.decodeUint())
+ keyIsPtr := mtyp.Key().Kind() == reflect.Ptr
+ elemIsPtr := mtyp.Elem().Kind() == reflect.Ptr
+ for i := 0; i < n; i++ {
+ key := decodeIntoValue(state, keyOp, keyIsPtr, allocValue(mtyp.Key()), ovfl)
+ elem := decodeIntoValue(state, elemOp, elemIsPtr, allocValue(mtyp.Elem()), ovfl)
+ value.SetMapIndex(key, elem)
+ }
+}
+
+// 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++ {
+ 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 < 0 || 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)
+ }
+ b := make([]byte, nr)
+ state.b.Read(b)
+ name := string(b)
+ // Allocate the destination interface value.
+ if name == "" {
+ // 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.
+ registerLock.RLock()
+ typ, ok := nameToConcreteType[name]
+ registerLock.RUnlock()
+ if !ok {
+ errorf("name not registered for interface: %q", name)
+ }
+ // 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.
+ b := make([]byte, state.decodeUint())
+ _, err := state.b.Read(b)
+ if err != nil {
+ error_(err)
+ }
+ id := dec.decodeTypeSequence(true)
+ if id < 0 {
+ error_(dec.err)
+ }
+ // At this point, the decoder buffer contains a delimited value. Just toss it.
+ state.b.Drop(int(state.decodeUint()))
+}
+
+// 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.
+ b := make([]byte, state.decodeUint())
+ _, err := state.b.Read(b)
+ if err != nil {
+ error_(err)
+ }
+ // 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.
+ b := make([]byte, state.decodeUint())
+ _, err := state.b.Read(b)
+ if err != nil {
+ error_(err)
+ }
+}
+
+// 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(t, 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, ut, 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) decOp {
+ op, ok := decIgnoreOpMap[wireId]
+ if !ok {
+ 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)
+ 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)
+ elemOp := dec.decIgnoreOpFor(elemId)
+ 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)
+ 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 {
+ 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) (engine *decEngine, err error) {
+ engine = new(decEngine)
+ engine.instr = make([]decInstr, 1) // one item
+ op := dec.decIgnoreOpFor(remoteId)
+ ovfl := overflow(dec.typeString(remoteId))
+ engine.instr[0] = decInstr{op, 0, nil, ovfl}
+ engine.numInstr = 1
+ return
+}
+
+// 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) {
+ 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)
+ 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{})
+
+// getDecEnginePtr 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, err = 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 {
+ if engine.numInstr == 0 && st.NumField() > 0 &&
+ dec.wireType[wireId] != nil && len(dec.wireType[wireId].StructT.Field) > 0 {
+ name := base.Name()
+ errorf("type mismatch: no fields matched compiling decoder for %s", name)
+ }
+ dec.decodeStruct(engine, ut, value)
+ } else {
+ dec.decodeSingle(engine, ut, 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()
+}
generated by cgit v1.2.3 (git 2.46.0) at 2025-10-31 04:12:05 +0000