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104f1574c8a217e3180d9ee0860fa7c19a98ee35
weave-scope/vendor/github.com/ugorji/go/codec/decode.go
Tom Wilkie bb755979b1 Add vendored dependancies
2015-10-24 11:19:50 +01:00

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// Copyright (c) 2012-2015 Ugorji Nwoke. All rights reserved.
// Use of this source code is governed by a MIT license found in the LICENSE file.
package codec
import (
"encoding"
"errors"
"fmt"
"io"
"reflect"
)
// Some tagging information for error messages.
const (
msgBadDesc = "Unrecognized descriptor byte"
msgDecCannotExpandArr = "cannot expand go array from %v to stream length: %v"
)
var (
onlyMapOrArrayCanDecodeIntoStructErr = errors.New("only encoded map or array can be decoded into a struct")
cannotDecodeIntoNilErr = errors.New("cannot decode into nil")
)
// decReader abstracts the reading source, allowing implementations that can
// read from an io.Reader or directly off a byte slice with zero-copying.
type decReader interface {
unreadn1()
// readx will use the implementation scratch buffer if possible i.e. n < len(scratchbuf), OR
// just return a view of the []byte being decoded from.
// Ensure you call detachZeroCopyBytes later if this needs to be sent outside codec control.
readx(n int) []byte
readb([]byte)
readn1() uint8
readn1eof() (v uint8, eof bool)
numread() int // number of bytes read
track()
stopTrack() []byte
}
type decReaderByteScanner interface {
io.Reader
io.ByteScanner
}
type decDriver interface {
// this will check if the next token is a break.
CheckBreak() bool
TryDecodeAsNil() bool
// check if a container type: vt is one of: Bytes, String, Nil, Slice or Map.
// if vt param == valueTypeNil, and nil is seen in stream, consume the nil.
IsContainerType(vt valueType) bool
IsBuiltinType(rt uintptr) bool
DecodeBuiltin(rt uintptr, v interface{})
//decodeNaked: Numbers are decoded as int64, uint64, float64 only (no smaller sized number types).
//for extensions, decodeNaked must completely decode them as a *RawExt.
//extensions should also use readx to decode them, for efficiency.
//kInterface will extract the detached byte slice if it has to pass it outside its realm.
DecodeNaked() (v interface{}, vt valueType, decodeFurther bool)
DecodeInt(bitsize uint8) (i int64)
DecodeUint(bitsize uint8) (ui uint64)
DecodeFloat(chkOverflow32 bool) (f float64)
DecodeBool() (b bool)
// DecodeString can also decode symbols.
// It looks redundant as DecodeBytes is available.
// However, some codecs (e.g. binc) support symbols and can
// return a pre-stored string value, meaning that it can bypass
// the cost of []byte->string conversion.
DecodeString() (s string)
// DecodeBytes may be called directly, without going through reflection.
// Consequently, it must be designed to handle possible nil.
DecodeBytes(bs []byte, isstring, zerocopy bool) (bsOut []byte)
// decodeExt will decode into a *RawExt or into an extension.
DecodeExt(v interface{}, xtag uint64, ext Ext) (realxtag uint64)
// decodeExt(verifyTag bool, tag byte) (xtag byte, xbs []byte)
ReadMapStart() int
ReadArrayStart() int
// ReadEnd registers the end of a map or array.
ReadEnd()
}
type decNoSeparator struct{}
func (_ decNoSeparator) ReadEnd() {}
type DecodeOptions struct {
// MapType specifies type to use during schema-less decoding of a map in the stream.
// If nil, we use map[interface{}]interface{}
MapType reflect.Type
// SliceType specifies type to use during schema-less decoding of an array in the stream.
// If nil, we use []interface{}
SliceType reflect.Type
// MaxInitLen defines the initial length that we "make" a collection (slice, chan or map) with.
// If 0 or negative, we default to a sensible value based on the size of an element in the collection.
//
// For example, when decoding, a stream may say that it has MAX_UINT elements.
// We should not auto-matically provision a slice of that length, to prevent Out-Of-Memory crash.
// Instead, we provision up to MaxInitLen, fill that up, and start appending after that.
MaxInitLen int
// If ErrorIfNoField, return an error when decoding a map
// from a codec stream into a struct, and no matching struct field is found.
ErrorIfNoField bool
// If ErrorIfNoArrayExpand, return an error when decoding a slice/array that cannot be expanded.
// For example, the stream contains an array of 8 items, but you are decoding into a [4]T array,
// or you are decoding into a slice of length 4 which is non-addressable (and so cannot be set).
ErrorIfNoArrayExpand bool
// If SignedInteger, use the int64 during schema-less decoding of unsigned values (not uint64).
SignedInteger bool
// MapValueReset controls how we decode into a map value.
//
// By default, we MAY retrieve the mapping for a key, and then decode into that.
// However, especially with big maps, that retrieval may be expensive and unnecessary
// if the stream already contains all that is necessary to recreate the value.
//
// If true, we will never retrieve the previous mapping,
// but rather decode into a new value and set that in the map.
//
// If false, we will retrieve the previous mapping if necessary e.g.
// the previous mapping is a pointer, or is a struct or array with pre-set state,
// or is an interface.
MapValueReset bool
// InterfaceReset controls how we decode into an interface.
//
// By default, when we see a field that is an interface{...},
// or a map with interface{...} value, we will attempt decoding into the
// "contained" value.
//
// However, this prevents us from reading a string into an interface{}
// that formerly contained a number.
//
// If true, we will decode into a new "blank" value, and set that in the interface.
// If false, we will decode into whatever is contained in the interface.
InterfaceReset bool
// InternString controls interning of strings during decoding.
//
// Some handles, e.g. json, typically will read map keys as strings.
// If the set of keys are finite, it may help reduce allocation to
// look them up from a map (than to allocate them afresh).
//
// Note: Handles will be smart when using the intern functionality.
// So everything will not be interned.
InternString bool
}
// ------------------------------------
// ioDecByteScanner implements Read(), ReadByte(...), UnreadByte(...) methods
// of io.Reader, io.ByteScanner.
type ioDecByteScanner struct {
r io.Reader
l byte // last byte
ls byte // last byte status. 0: init-canDoNothing, 1: canRead, 2: canUnread
b [1]byte // tiny buffer for reading single bytes
}
func (z *ioDecByteScanner) Read(p []byte) (n int, err error) {
var firstByte bool
if z.ls == 1 {
z.ls = 2
p[0] = z.l
if len(p) == 1 {
n = 1
return
}
firstByte = true
p = p[1:]
}
n, err = z.r.Read(p)
if n > 0 {
if err == io.EOF && n == len(p) {
err = nil // read was successful, so postpone EOF (till next time)
}
z.l = p[n-1]
z.ls = 2
}
if firstByte {
n++
}
return
}
func (z *ioDecByteScanner) ReadByte() (c byte, err error) {
n, err := z.Read(z.b[:])
if n == 1 {
c = z.b[0]
if err == io.EOF {
err = nil // read was successful, so postpone EOF (till next time)
}
}
return
}
func (z *ioDecByteScanner) UnreadByte() (err error) {
x := z.ls
if x == 0 {
err = errors.New("cannot unread - nothing has been read")
} else if x == 1 {
err = errors.New("cannot unread - last byte has not been read")
} else if x == 2 {
z.ls = 1
}
return
}
// ioDecReader is a decReader that reads off an io.Reader
type ioDecReader struct {
br decReaderByteScanner
// temp byte array re-used internally for efficiency during read.
// shares buffer with Decoder, so we keep size of struct within 8 words.
x *[scratchByteArrayLen]byte
bs ioDecByteScanner
n int // num read
tr []byte // tracking bytes read
trb bool
}
func (z *ioDecReader) numread() int {
return z.n
}
func (z *ioDecReader) readx(n int) (bs []byte) {
if n <= 0 {
return
}
if n < len(z.x) {
bs = z.x[:n]
} else {
bs = make([]byte, n)
}
if _, err := io.ReadAtLeast(z.br, bs, n); err != nil {
panic(err)
}
z.n += len(bs)
if z.trb {
z.tr = append(z.tr, bs...)
}
return
}
func (z *ioDecReader) readb(bs []byte) {
if len(bs) == 0 {
return
}
n, err := io.ReadAtLeast(z.br, bs, len(bs))
z.n += n
if err != nil {
panic(err)
}
if z.trb {
z.tr = append(z.tr, bs...)
}
}
func (z *ioDecReader) readn1() (b uint8) {
b, err := z.br.ReadByte()
if err != nil {
panic(err)
}
z.n++
if z.trb {
z.tr = append(z.tr, b)
}
return b
}
func (z *ioDecReader) readn1eof() (b uint8, eof bool) {
b, err := z.br.ReadByte()
if err == nil {
z.n++
if z.trb {
z.tr = append(z.tr, b)
}
} else if err == io.EOF {
eof = true
} else {
panic(err)
}
return
}
func (z *ioDecReader) unreadn1() {
err := z.br.UnreadByte()
if err != nil {
panic(err)
}
z.n--
if z.trb {
if l := len(z.tr) - 1; l >= 0 {
z.tr = z.tr[:l]
}
}
}
func (z *ioDecReader) track() {
if z.tr != nil {
z.tr = z.tr[:0]
}
z.trb = true
}
func (z *ioDecReader) stopTrack() (bs []byte) {
z.trb = false
return z.tr
}
// ------------------------------------
var bytesDecReaderCannotUnreadErr = errors.New("cannot unread last byte read")
// bytesDecReader is a decReader that reads off a byte slice with zero copying
type bytesDecReader struct {
b []byte // data
c int // cursor
a int // available
t int // track start
}
func (z *bytesDecReader) numread() int {
return z.c
}
func (z *bytesDecReader) unreadn1() {
if z.c == 0 || len(z.b) == 0 {
panic(bytesDecReaderCannotUnreadErr)
}
z.c--
z.a++
return
}
func (z *bytesDecReader) readx(n int) (bs []byte) {
// slicing from a non-constant start position is more expensive,
// as more computation is required to decipher the pointer start position.
// However, we do it only once, and it's better than reslicing both z.b and return value.
if n <= 0 {
} else if z.a == 0 {
panic(io.EOF)
} else if n > z.a {
panic(io.ErrUnexpectedEOF)
} else {
c0 := z.c
z.c = c0 + n
z.a = z.a - n
bs = z.b[c0:z.c]
}
return
}
func (z *bytesDecReader) readn1() (v uint8) {
if z.a == 0 {
panic(io.EOF)
}
v = z.b[z.c]
z.c++
z.a--
return
}
func (z *bytesDecReader) readn1eof() (v uint8, eof bool) {
if z.a == 0 {
eof = true
return
}
v = z.b[z.c]
z.c++
z.a--
return
}
func (z *bytesDecReader) readb(bs []byte) {
copy(bs, z.readx(len(bs)))
}
func (z *bytesDecReader) track() {
z.t = z.c
}
func (z *bytesDecReader) stopTrack() (bs []byte) {
return z.b[z.t:z.c]
}
// ------------------------------------
type decFnInfo struct {
d *Decoder
ti *typeInfo
xfFn Ext
xfTag uint64
seq seqType
}
// ----------------------------------------
type decFn struct {
i decFnInfo
f func(*decFnInfo, reflect.Value)
}
func (f *decFnInfo) builtin(rv reflect.Value) {
f.d.d.DecodeBuiltin(f.ti.rtid, rv.Addr().Interface())
}
func (f *decFnInfo) rawExt(rv reflect.Value) {
f.d.d.DecodeExt(rv.Addr().Interface(), 0, nil)
}
func (f *decFnInfo) ext(rv reflect.Value) {
f.d.d.DecodeExt(rv.Addr().Interface(), f.xfTag, f.xfFn)
}
func (f *decFnInfo) getValueForUnmarshalInterface(rv reflect.Value, indir int8) (v interface{}) {
if indir == -1 {
v = rv.Addr().Interface()
} else if indir == 0 {
v = rv.Interface()
} else {
for j := int8(0); j < indir; j++ {
if rv.IsNil() {
rv.Set(reflect.New(rv.Type().Elem()))
}
rv = rv.Elem()
}
v = rv.Interface()
}
return
}
func (f *decFnInfo) selferUnmarshal(rv reflect.Value) {
f.getValueForUnmarshalInterface(rv, f.ti.csIndir).(Selfer).CodecDecodeSelf(f.d)
}
func (f *decFnInfo) binaryUnmarshal(rv reflect.Value) {
bm := f.getValueForUnmarshalInterface(rv, f.ti.bunmIndir).(encoding.BinaryUnmarshaler)
xbs := f.d.d.DecodeBytes(nil, false, true)
if fnerr := bm.UnmarshalBinary(xbs); fnerr != nil {
panic(fnerr)
}
}
func (f *decFnInfo) textUnmarshal(rv reflect.Value) {
tm := f.getValueForUnmarshalInterface(rv, f.ti.tunmIndir).(encoding.TextUnmarshaler)
fnerr := tm.UnmarshalText(f.d.d.DecodeBytes(f.d.b[:], true, true))
if fnerr != nil {
panic(fnerr)
}
}
func (f *decFnInfo) jsonUnmarshal(rv reflect.Value) {
tm := f.getValueForUnmarshalInterface(rv, f.ti.junmIndir).(jsonUnmarshaler)
// bs := f.d.d.DecodeBytes(f.d.b[:], true, true)
// grab the bytes to be read, as UnmarshalJSON wants the full JSON to unmarshal it itself.
f.d.r.track()
f.d.swallow()
bs := f.d.r.stopTrack()
// fmt.Printf(">>>>>> REFLECTION JSON: %s\n", bs)
fnerr := tm.UnmarshalJSON(bs)
if fnerr != nil {
panic(fnerr)
}
}
func (f *decFnInfo) kErr(rv reflect.Value) {
f.d.errorf("no decoding function defined for kind %v", rv.Kind())
}
func (f *decFnInfo) kString(rv reflect.Value) {
rv.SetString(f.d.d.DecodeString())
}
func (f *decFnInfo) kBool(rv reflect.Value) {
rv.SetBool(f.d.d.DecodeBool())
}
func (f *decFnInfo) kInt(rv reflect.Value) {
rv.SetInt(f.d.d.DecodeInt(intBitsize))
}
func (f *decFnInfo) kInt64(rv reflect.Value) {
rv.SetInt(f.d.d.DecodeInt(64))
}
func (f *decFnInfo) kInt32(rv reflect.Value) {
rv.SetInt(f.d.d.DecodeInt(32))
}
func (f *decFnInfo) kInt8(rv reflect.Value) {
rv.SetInt(f.d.d.DecodeInt(8))
}
func (f *decFnInfo) kInt16(rv reflect.Value) {
rv.SetInt(f.d.d.DecodeInt(16))
}
func (f *decFnInfo) kFloat32(rv reflect.Value) {
rv.SetFloat(f.d.d.DecodeFloat(true))
}
func (f *decFnInfo) kFloat64(rv reflect.Value) {
rv.SetFloat(f.d.d.DecodeFloat(false))
}
func (f *decFnInfo) kUint8(rv reflect.Value) {
rv.SetUint(f.d.d.DecodeUint(8))
}
func (f *decFnInfo) kUint64(rv reflect.Value) {
rv.SetUint(f.d.d.DecodeUint(64))
}
func (f *decFnInfo) kUint(rv reflect.Value) {
rv.SetUint(f.d.d.DecodeUint(uintBitsize))
}
func (f *decFnInfo) kUintptr(rv reflect.Value) {
rv.SetUint(f.d.d.DecodeUint(uintBitsize))
}
func (f *decFnInfo) kUint32(rv reflect.Value) {
rv.SetUint(f.d.d.DecodeUint(32))
}
func (f *decFnInfo) kUint16(rv reflect.Value) {
rv.SetUint(f.d.d.DecodeUint(16))
}
// func (f *decFnInfo) kPtr(rv reflect.Value) {
// debugf(">>>>>>> ??? decode kPtr called - shouldn't get called")
// if rv.IsNil() {
// rv.Set(reflect.New(rv.Type().Elem()))
// }
// f.d.decodeValue(rv.Elem())
// }
// var kIntfCtr uint64
func (f *decFnInfo) kInterfaceNaked() (rvn reflect.Value) {
// nil interface:
// use some hieristics to decode it appropriately
// based on the detected next value in the stream.
v, vt, decodeFurther := f.d.d.DecodeNaked()
if vt == valueTypeNil {
return
}
// We cannot decode non-nil stream value into nil interface with methods (e.g. io.Reader).
if num := f.ti.rt.NumMethod(); num > 0 {
f.d.errorf("cannot decode non-nil codec value into nil %v (%v methods)", f.ti.rt, num)
return
}
var useRvn bool
switch vt {
case valueTypeMap:
if f.d.h.MapType == nil {
var m2 map[interface{}]interface{}
v = &m2
} else {
rvn = reflect.New(f.d.h.MapType).Elem()
useRvn = true
}
case valueTypeArray:
if f.d.h.SliceType == nil {
var m2 []interface{}
v = &m2
} else {
rvn = reflect.New(f.d.h.SliceType).Elem()
useRvn = true
}
case valueTypeExt:
re := v.(*RawExt)
bfn := f.d.h.getExtForTag(re.Tag)
if bfn == nil {
re.Data = detachZeroCopyBytes(f.d.bytes, nil, re.Data)
rvn = reflect.ValueOf(*re)
} else {
rvnA := reflect.New(bfn.rt)
rvn = rvnA.Elem()
if re.Data != nil {
bfn.ext.ReadExt(rvnA.Interface(), re.Data)
} else {
bfn.ext.UpdateExt(rvnA.Interface(), re.Value)
}
}
return
}
if decodeFurther {
if useRvn {
f.d.decodeValue(rvn, nil)
} else if v != nil {
// this v is a pointer, so we need to dereference it when done
f.d.decode(v)
rvn = reflect.ValueOf(v).Elem()
useRvn = true
}
}
if !useRvn && v != nil {
rvn = reflect.ValueOf(v)
}
return
}
func (f *decFnInfo) kInterface(rv reflect.Value) {
// debugf("\t===> kInterface")
// Note:
// A consequence of how kInterface works, is that
// if an interface already contains something, we try
// to decode into what was there before.
// We do not replace with a generic value (as got from decodeNaked).
var rvn reflect.Value
if rv.IsNil() {
rvn = f.kInterfaceNaked()
if rvn.IsValid() {
rv.Set(rvn)
}
} else if f.d.h.InterfaceReset {
rvn = f.kInterfaceNaked()
if rvn.IsValid() {
rv.Set(rvn)
} else {
// reset to zero value based on current type in there.
rv.Set(reflect.Zero(rv.Elem().Type()))
}
} else {
rvn = rv.Elem()
// Note: interface{} is settable, but underlying type may not be.
// Consequently, we have to set the reflect.Value directly.
// if underlying type is settable (e.g. ptr or interface),
// we just decode into it.
// Else we create a settable value, decode into it, and set on the interface.
if rvn.CanSet() {
f.d.decodeValue(rvn, nil)
} else {
rvn2 := reflect.New(rvn.Type()).Elem()
rvn2.Set(rvn)
f.d.decodeValue(rvn2, nil)
rv.Set(rvn2)
}
}
}
func (f *decFnInfo) kStruct(rv reflect.Value) {
fti := f.ti
d := f.d
dd := d.d
if dd.IsContainerType(valueTypeMap) {
containerLen := dd.ReadMapStart()
if containerLen == 0 {
dd.ReadEnd()
return
}
tisfi := fti.sfi
hasLen := containerLen >= 0
if hasLen {
for j := 0; j < containerLen; j++ {
// rvkencname := dd.DecodeString()
rvkencname := stringView(dd.DecodeBytes(f.d.b[:], true, true))
// rvksi := ti.getForEncName(rvkencname)
if k := fti.indexForEncName(rvkencname); k > -1 {
si := tisfi[k]
if dd.TryDecodeAsNil() {
si.setToZeroValue(rv)
} else {
d.decodeValue(si.field(rv, true), nil)
}
} else {
d.structFieldNotFound(-1, rvkencname)
}
}
} else {
for j := 0; !dd.CheckBreak(); j++ {
// rvkencname := dd.DecodeString()
rvkencname := stringView(dd.DecodeBytes(f.d.b[:], true, true))
// rvksi := ti.getForEncName(rvkencname)
if k := fti.indexForEncName(rvkencname); k > -1 {
si := tisfi[k]
if dd.TryDecodeAsNil() {
si.setToZeroValue(rv)
} else {
d.decodeValue(si.field(rv, true), nil)
}
} else {
d.structFieldNotFound(-1, rvkencname)
}
}
dd.ReadEnd()
}
} else if dd.IsContainerType(valueTypeArray) {
containerLen := dd.ReadArrayStart()
if containerLen == 0 {
dd.ReadEnd()
return
}
// Not much gain from doing it two ways for array.
// Arrays are not used as much for structs.
hasLen := containerLen >= 0
for j, si := range fti.sfip {
if hasLen {
if j == containerLen {
break
}
} else if dd.CheckBreak() {
break
}
if dd.TryDecodeAsNil() {
si.setToZeroValue(rv)
} else {
d.decodeValue(si.field(rv, true), nil)
}
}
if containerLen > len(fti.sfip) {
// read remaining values and throw away
for j := len(fti.sfip); j < containerLen; j++ {
d.structFieldNotFound(j, "")
}
}
dd.ReadEnd()
} else {
f.d.error(onlyMapOrArrayCanDecodeIntoStructErr)
return
}
}
func (f *decFnInfo) kSlice(rv reflect.Value) {
// A slice can be set from a map or array in stream.
// This way, the order can be kept (as order is lost with map).
ti := f.ti
d := f.d
dd := d.d
rtelem0 := ti.rt.Elem()
if dd.IsContainerType(valueTypeBytes) || dd.IsContainerType(valueTypeString) {
if ti.rtid == uint8SliceTypId || rtelem0.Kind() == reflect.Uint8 {
if f.seq == seqTypeChan {
bs2 := dd.DecodeBytes(nil, false, true)
ch := rv.Interface().(chan<- byte)
for _, b := range bs2 {
ch <- b
}
} else {
rvbs := rv.Bytes()
bs2 := dd.DecodeBytes(rvbs, false, false)
if rvbs == nil && bs2 != nil || rvbs != nil && bs2 == nil || len(bs2) != len(rvbs) {
if rv.CanSet() {
rv.SetBytes(bs2)
} else {
copy(rvbs, bs2)
}
}
}
return
}
}
// array := f.seq == seqTypeChan
slh, containerLenS := d.decSliceHelperStart()
var rvlen, numToRead int
var truncated bool // says that the len of the sequence is not same as the expected number of elements.
numToRead = containerLenS // if truncated, reset numToRead
// an array can never return a nil slice. so no need to check f.array here.
if rv.IsNil() {
// either chan or slice
if rvlen, truncated = decInferLen(containerLenS, f.d.h.MaxInitLen, int(rtelem0.Size())); truncated {
numToRead = rvlen
}
if f.seq == seqTypeSlice {
rv.Set(reflect.MakeSlice(ti.rt, rvlen, rvlen))
} else if f.seq == seqTypeChan {
rv.Set(reflect.MakeChan(ti.rt, rvlen))
}
} else {
rvlen = rv.Len()
}
if containerLenS == 0 {
if f.seq == seqTypeSlice && rvlen != 0 {
rv.SetLen(0)
}
// dd.ReadEnd()
return
}
rtelem := rtelem0
for rtelem.Kind() == reflect.Ptr {
rtelem = rtelem.Elem()
}
fn := d.getDecFn(rtelem, true, true)
var rv0, rv9 reflect.Value
rv0 = rv
rvChanged := false
rvcap := rv.Cap()
// for j := 0; j < containerLenS; j++ {
if containerLenS >= 0 { // hasLen
if f.seq == seqTypeChan {
// handle chan specially:
for j := 0; j < containerLenS; j++ {
rv9 = reflect.New(rtelem0).Elem()
d.decodeValue(rv9, fn)
rv.Send(rv9)
}
} else { // slice or array
if containerLenS > rvcap {
if f.seq == seqTypeArray {
d.arrayCannotExpand(rvlen, containerLenS)
} else {
oldRvlenGtZero := rvlen > 0
rvlen, truncated = decInferLen(containerLenS, f.d.h.MaxInitLen, int(rtelem0.Size()))
rv = reflect.MakeSlice(ti.rt, rvlen, rvlen)
if oldRvlenGtZero && !isImmutableKind(rtelem0.Kind()) {
reflect.Copy(rv, rv0) // only copy up to length NOT cap i.e. rv0.Slice(0, rvcap)
}
rvChanged = true
}
numToRead = rvlen
} else if containerLenS != rvlen {
if f.seq == seqTypeSlice {
rv.SetLen(containerLenS)
rvlen = containerLenS
}
}
j := 0
// we read up to the numToRead
for ; j < numToRead; j++ {
d.decodeValue(rv.Index(j), fn)
}
// if slice, expand and read up to containerLenS (or EOF) iff truncated
// if array, swallow all the rest.
if f.seq == seqTypeArray {
for ; j < containerLenS; j++ {
d.swallow()
}
} else if truncated { // slice was truncated, as chan NOT in this block
for ; j < containerLenS; j++ {
rv = expandSliceValue(rv, 1)
rv9 = rv.Index(j)
if resetSliceElemToZeroValue {
rv9.Set(reflect.Zero(rtelem0))
}
d.decodeValue(rv9, fn)
}
}
}
} else {
for j := 0; !dd.CheckBreak(); j++ {
var decodeIntoBlank bool
// if indefinite, etc, then expand the slice if necessary
if j >= rvlen {
if f.seq == seqTypeArray {
d.arrayCannotExpand(rvlen, j+1)
decodeIntoBlank = true
} else if f.seq == seqTypeSlice {
// rv = reflect.Append(rv, reflect.Zero(rtelem0)) // uses append logic, plus varargs
rv = expandSliceValue(rv, 1)
rv9 = rv.Index(j)
// rv.Index(rv.Len() - 1).Set(reflect.Zero(rtelem0))
if resetSliceElemToZeroValue {
rv9.Set(reflect.Zero(rtelem0))
}
rvlen++
rvChanged = true
}
} else if f.seq != seqTypeChan { // slice or array
rv9 = rv.Index(j)
}
if f.seq == seqTypeChan {
rv9 = reflect.New(rtelem0).Elem()
d.decodeValue(rv9, fn)
rv.Send(rv9)
} else if decodeIntoBlank {
d.swallow()
} else { // seqTypeSlice
d.decodeValue(rv9, fn)
}
}
slh.End()
}
if rvChanged {
rv0.Set(rv)
}
}
func (f *decFnInfo) kArray(rv reflect.Value) {
// f.d.decodeValue(rv.Slice(0, rv.Len()))
f.kSlice(rv.Slice(0, rv.Len()))
}
func (f *decFnInfo) kMap(rv reflect.Value) {
d := f.d
dd := d.d
containerLen := dd.ReadMapStart()
ti := f.ti
if rv.IsNil() {
rv.Set(reflect.MakeMap(ti.rt))
}
if containerLen == 0 {
// It is not length-prefix style container. They have no End marker.
// dd.ReadMapEnd()
return
}
ktype, vtype := ti.rt.Key(), ti.rt.Elem()
ktypeId := reflect.ValueOf(ktype).Pointer()
var keyFn, valFn *decFn
var xtyp reflect.Type
for xtyp = ktype; xtyp.Kind() == reflect.Ptr; xtyp = xtyp.Elem() {
}
keyFn = d.getDecFn(xtyp, true, true)
for xtyp = vtype; xtyp.Kind() == reflect.Ptr; xtyp = xtyp.Elem() {
}
valFn = d.getDecFn(xtyp, true, true)
var mapGet bool
if !f.d.h.MapValueReset {
// if pointer, mapGet = true
// if interface, mapGet = true if !DecodeNakedAlways (else false)
// if builtin, mapGet = false
// else mapGet = true
vtypeKind := vtype.Kind()
if vtypeKind == reflect.Ptr {
mapGet = true
} else if vtypeKind == reflect.Interface {
if !f.d.h.InterfaceReset {
mapGet = true
}
} else if !isImmutableKind(vtypeKind) {
mapGet = true
}
}
var rvk, rvv reflect.Value
// for j := 0; j < containerLen; j++ {
if containerLen > 0 {
for j := 0; j < containerLen; j++ {
rvk = reflect.New(ktype).Elem()
d.decodeValue(rvk, keyFn)
// special case if a byte array.
if ktypeId == intfTypId {
rvk = rvk.Elem()
if rvk.Type() == uint8SliceTyp {
rvk = reflect.ValueOf(d.string(rvk.Bytes()))
}
}
if mapGet {
rvv = rv.MapIndex(rvk)
if !rvv.IsValid() {
rvv = reflect.New(vtype).Elem()
}
} else {
rvv = reflect.New(vtype).Elem()
}
d.decodeValue(rvv, valFn)
rv.SetMapIndex(rvk, rvv)
}
} else {
for j := 0; !dd.CheckBreak(); j++ {
rvk = reflect.New(ktype).Elem()
d.decodeValue(rvk, keyFn)
// special case if a byte array.
if ktypeId == intfTypId {
rvk = rvk.Elem()
if rvk.Type() == uint8SliceTyp {
rvk = reflect.ValueOf(d.string(rvk.Bytes()))
}
}
if mapGet {
rvv = rv.MapIndex(rvk)
if !rvv.IsValid() {
rvv = reflect.New(vtype).Elem()
}
} else {
rvv = reflect.New(vtype).Elem()
}
d.decodeValue(rvv, valFn)
rv.SetMapIndex(rvk, rvv)
}
dd.ReadEnd()
}
}
type decRtidFn struct {
rtid uintptr
fn decFn
}
// A Decoder reads and decodes an object from an input stream in the codec format.
type Decoder struct {
// hopefully, reduce derefencing cost by laying the decReader inside the Decoder.
// Try to put things that go together to fit within a cache line (8 words).
d decDriver
// NOTE: Decoder shouldn't call it's read methods,
// as the handler MAY need to do some coordination.
r decReader
// sa [initCollectionCap]decRtidFn
s []decRtidFn
h *BasicHandle
rb bytesDecReader
hh Handle
be bool // is binary encoding
bytes bool // is bytes reader
js bool // is json handle
ri ioDecReader
f map[uintptr]*decFn
is map[string]string // used for interning strings
// _ uintptr // for alignment purposes, so next one starts from a cache line
b [scratchByteArrayLen]byte
}
// NewDecoder returns a Decoder for decoding a stream of bytes from an io.Reader.
//
// For efficiency, Users are encouraged to pass in a memory buffered reader
// (eg bufio.Reader, bytes.Buffer).
func NewDecoder(r io.Reader, h Handle) (d *Decoder) {
d = &Decoder{hh: h, h: h.getBasicHandle(), be: h.isBinary()}
// d.s = d.sa[:0]
d.ri.x = &d.b
d.ri.bs.r = r
var ok bool
d.ri.br, ok = r.(decReaderByteScanner)
if !ok {
d.ri.br = &d.ri.bs
}
d.r = &d.ri
if d.h.InternString {
d.is = make(map[string]string, 32)
}
_, d.js = h.(*JsonHandle)
d.d = h.newDecDriver(d)
return
}
// NewDecoderBytes returns a Decoder which efficiently decodes directly
// from a byte slice with zero copying.
func NewDecoderBytes(in []byte, h Handle) (d *Decoder) {
d = &Decoder{hh: h, h: h.getBasicHandle(), be: h.isBinary(), bytes: true}
// d.s = d.sa[:0]
d.rb.b = in
d.rb.a = len(in)
d.r = &d.rb
if d.h.InternString {
d.is = make(map[string]string, 32)
}
_, d.js = h.(*JsonHandle)
d.d = h.newDecDriver(d)
// d.d = h.newDecDriver(decReaderT{true, &d.rb, &d.ri})
return
}
// Decode decodes the stream from reader and stores the result in the
// value pointed to by v. v cannot be a nil pointer. v can also be
// a reflect.Value of a pointer.
//
// Note that a pointer to a nil interface is not a nil pointer.
// If you do not know what type of stream it is, pass in a pointer to a nil interface.
// We will decode and store a value in that nil interface.
//
// Sample usages:
// // Decoding into a non-nil typed value
// var f float32
// err = codec.NewDecoder(r, handle).Decode(&f)
//
// // Decoding into nil interface
// var v interface{}
// dec := codec.NewDecoder(r, handle)
// err = dec.Decode(&v)
//
// When decoding into a nil interface{}, we will decode into an appropriate value based
// on the contents of the stream:
// - Numbers are decoded as float64, int64 or uint64.
// - Other values are decoded appropriately depending on the type:
// bool, string, []byte, time.Time, etc
// - Extensions are decoded as RawExt (if no ext function registered for the tag)
// Configurations exist on the Handle to override defaults
// (e.g. for MapType, SliceType and how to decode raw bytes).
//
// When decoding into a non-nil interface{} value, the mode of encoding is based on the
// type of the value. When a value is seen:
// - If an extension is registered for it, call that extension function
// - If it implements BinaryUnmarshaler, call its UnmarshalBinary(data []byte) error
// - Else decode it based on its reflect.Kind
//
// There are some special rules when decoding into containers (slice/array/map/struct).
// Decode will typically use the stream contents to UPDATE the container.
// - A map can be decoded from a stream map, by updating matching keys.
// - A slice can be decoded from a stream array,
// by updating the first n elements, where n is length of the stream.
// - A slice can be decoded from a stream map, by decoding as if
// it contains a sequence of key-value pairs.
// - A struct can be decoded from a stream map, by updating matching fields.
// - A struct can be decoded from a stream array,
// by updating fields as they occur in the struct (by index).
//
// When decoding a stream map or array with length of 0 into a nil map or slice,
// we reset the destination map or slice to a zero-length value.
//
// However, when decoding a stream nil, we reset the destination container
// to its "zero" value (e.g. nil for slice/map, etc).
//
func (d *Decoder) Decode(v interface{}) (err error) {
defer panicToErr(&err)
d.decode(v)
return
}
// this is not a smart swallow, as it allocates objects and does unnecessary work.
func (d *Decoder) swallowViaHammer() {
var blank interface{}
d.decodeValue(reflect.ValueOf(&blank).Elem(), nil)
}
func (d *Decoder) swallow() {
// smarter decode that just swallows the content
dd := d.d
switch {
case dd.TryDecodeAsNil():
case dd.IsContainerType(valueTypeMap):
containerLen := dd.ReadMapStart()
clenGtEqualZero := containerLen >= 0
for j := 0; ; j++ {
if clenGtEqualZero {
if j >= containerLen {
break
}
} else if dd.CheckBreak() {
break
}
d.swallow()
d.swallow()
}
dd.ReadEnd()
case dd.IsContainerType(valueTypeArray):
containerLenS := dd.ReadArrayStart()
clenGtEqualZero := containerLenS >= 0
for j := 0; ; j++ {
if clenGtEqualZero {
if j >= containerLenS {
break
}
} else if dd.CheckBreak() {
break
}
d.swallow()
}
dd.ReadEnd()
case dd.IsContainerType(valueTypeBytes):
dd.DecodeBytes(d.b[:], false, true)
case dd.IsContainerType(valueTypeString):
dd.DecodeBytes(d.b[:], true, true)
// dd.DecodeStringAsBytes(d.b[:])
default:
// these are all primitives, which we can get from decodeNaked
dd.DecodeNaked()
}
}
// MustDecode is like Decode, but panics if unable to Decode.
// This provides insight to the code location that triggered the error.
func (d *Decoder) MustDecode(v interface{}) {
d.decode(v)
}
func (d *Decoder) decode(iv interface{}) {
// if ics, ok := iv.(Selfer); ok {
// ics.CodecDecodeSelf(d)
// return
// }
if d.d.TryDecodeAsNil() {
switch v := iv.(type) {
case nil:
case *string:
*v = ""
case *bool:
*v = false
case *int:
*v = 0
case *int8:
*v = 0
case *int16:
*v = 0
case *int32:
*v = 0
case *int64:
*v = 0
case *uint:
*v = 0
case *uint8:
*v = 0
case *uint16:
*v = 0
case *uint32:
*v = 0
case *uint64:
*v = 0
case *float32:
*v = 0
case *float64:
*v = 0
case *[]uint8:
*v = nil
case reflect.Value:
d.chkPtrValue(v)
v = v.Elem()
if v.IsValid() {
v.Set(reflect.Zero(v.Type()))
}
default:
rv := reflect.ValueOf(iv)
d.chkPtrValue(rv)
rv = rv.Elem()
if rv.IsValid() {
rv.Set(reflect.Zero(rv.Type()))
}
}
return
}
switch v := iv.(type) {
case nil:
d.error(cannotDecodeIntoNilErr)
return
case Selfer:
v.CodecDecodeSelf(d)
case reflect.Value:
d.chkPtrValue(v)
d.decodeValueNotNil(v.Elem(), nil)
case *string:
*v = d.d.DecodeString()
case *bool:
*v = d.d.DecodeBool()
case *int:
*v = int(d.d.DecodeInt(intBitsize))
case *int8:
*v = int8(d.d.DecodeInt(8))
case *int16:
*v = int16(d.d.DecodeInt(16))
case *int32:
*v = int32(d.d.DecodeInt(32))
case *int64:
*v = d.d.DecodeInt(64)
case *uint:
*v = uint(d.d.DecodeUint(uintBitsize))
case *uint8:
*v = uint8(d.d.DecodeUint(8))
case *uint16:
*v = uint16(d.d.DecodeUint(16))
case *uint32:
*v = uint32(d.d.DecodeUint(32))
case *uint64:
*v = d.d.DecodeUint(64)
case *float32:
*v = float32(d.d.DecodeFloat(true))
case *float64:
*v = d.d.DecodeFloat(false)
case *[]uint8:
*v = d.d.DecodeBytes(*v, false, false)
case *interface{}:
d.decodeValueNotNil(reflect.ValueOf(iv).Elem(), nil)
default:
if !fastpathDecodeTypeSwitch(iv, d) {
d.decodeI(iv, true, false, false, false)
}
}
}
func (d *Decoder) preDecodeValue(rv reflect.Value, tryNil bool) (rv2 reflect.Value, proceed bool) {
if tryNil && d.d.TryDecodeAsNil() {
// No need to check if a ptr, recursively, to determine
// whether to set value to nil.
// Just always set value to its zero type.
if rv.IsValid() { // rv.CanSet() // always settable, except it's invalid
rv.Set(reflect.Zero(rv.Type()))
}
return
}
// If stream is not containing a nil value, then we can deref to the base
// non-pointer value, and decode into that.
for rv.Kind() == reflect.Ptr {
if rv.IsNil() {
rv.Set(reflect.New(rv.Type().Elem()))
}
rv = rv.Elem()
}
return rv, true
}
func (d *Decoder) decodeI(iv interface{}, checkPtr, tryNil, checkFastpath, checkCodecSelfer bool) {
rv := reflect.ValueOf(iv)
if checkPtr {
d.chkPtrValue(rv)
}
rv, proceed := d.preDecodeValue(rv, tryNil)
if proceed {
fn := d.getDecFn(rv.Type(), checkFastpath, checkCodecSelfer)
fn.f(&fn.i, rv)
}
}
func (d *Decoder) decodeValue(rv reflect.Value, fn *decFn) {
if rv, proceed := d.preDecodeValue(rv, true); proceed {
if fn == nil {
fn = d.getDecFn(rv.Type(), true, true)
}
fn.f(&fn.i, rv)
}
}
func (d *Decoder) decodeValueNotNil(rv reflect.Value, fn *decFn) {
if rv, proceed := d.preDecodeValue(rv, false); proceed {
if fn == nil {
fn = d.getDecFn(rv.Type(), true, true)
}
fn.f(&fn.i, rv)
}
}
func (d *Decoder) getDecFn(rt reflect.Type, checkFastpath, checkCodecSelfer bool) (fn *decFn) {
rtid := reflect.ValueOf(rt).Pointer()
// retrieve or register a focus'ed function for this type
// to eliminate need to do the retrieval multiple times
// if d.f == nil && d.s == nil { debugf("---->Creating new dec f map for type: %v\n", rt) }
var ok bool
if useMapForCodecCache {
fn, ok = d.f[rtid]
} else {
for i := range d.s {
v := &(d.s[i])
if v.rtid == rtid {
fn, ok = &(v.fn), true
break
}
}
}
if ok {
return
}
if useMapForCodecCache {
if d.f == nil {
d.f = make(map[uintptr]*decFn, initCollectionCap)
}
fn = new(decFn)
d.f[rtid] = fn
} else {
if d.s == nil {
d.s = make([]decRtidFn, 0, initCollectionCap)
}
d.s = append(d.s, decRtidFn{rtid: rtid})
fn = &(d.s[len(d.s)-1]).fn
}
// debugf("\tCreating new dec fn for type: %v\n", rt)
ti := d.h.getTypeInfo(rtid, rt)
fi := &(fn.i)
fi.d = d
fi.ti = ti
// An extension can be registered for any type, regardless of the Kind
// (e.g. type BitSet int64, type MyStruct { / * unexported fields * / }, type X []int, etc.
//
// We can't check if it's an extension byte here first, because the user may have
// registered a pointer or non-pointer type, meaning we may have to recurse first
// before matching a mapped type, even though the extension byte is already detected.
//
// NOTE: if decoding into a nil interface{}, we return a non-nil
// value except even if the container registers a length of 0.
if checkCodecSelfer && ti.cs {
fn.f = (*decFnInfo).selferUnmarshal
} else if rtid == rawExtTypId {
fn.f = (*decFnInfo).rawExt
} else if d.d.IsBuiltinType(rtid) {
fn.f = (*decFnInfo).builtin
} else if xfFn := d.h.getExt(rtid); xfFn != nil {
fi.xfTag, fi.xfFn = xfFn.tag, xfFn.ext
fn.f = (*decFnInfo).ext
} else if supportMarshalInterfaces && d.be && ti.bunm {
fn.f = (*decFnInfo).binaryUnmarshal
} else if supportMarshalInterfaces && !d.be && d.js && ti.junm {
//If JSON, we should check JSONUnmarshal before textUnmarshal
fn.f = (*decFnInfo).jsonUnmarshal
} else if supportMarshalInterfaces && !d.be && ti.tunm {
fn.f = (*decFnInfo).textUnmarshal
} else {
rk := rt.Kind()
if fastpathEnabled && checkFastpath && (rk == reflect.Map || rk == reflect.Slice) {
if rt.PkgPath() == "" {
if idx := fastpathAV.index(rtid); idx != -1 {
fn.f = fastpathAV[idx].decfn
}
} else {
// use mapping for underlying type if there
ok = false
var rtu reflect.Type
if rk == reflect.Map {
rtu = reflect.MapOf(rt.Key(), rt.Elem())
} else {
rtu = reflect.SliceOf(rt.Elem())
}
rtuid := reflect.ValueOf(rtu).Pointer()
if idx := fastpathAV.index(rtuid); idx != -1 {
xfnf := fastpathAV[idx].decfn
xrt := fastpathAV[idx].rt
fn.f = func(xf *decFnInfo, xrv reflect.Value) {
// xfnf(xf, xrv.Convert(xrt))
xfnf(xf, xrv.Addr().Convert(reflect.PtrTo(xrt)).Elem())
}
}
}
}
if fn.f == nil {
switch rk {
case reflect.String:
fn.f = (*decFnInfo).kString
case reflect.Bool:
fn.f = (*decFnInfo).kBool
case reflect.Int:
fn.f = (*decFnInfo).kInt
case reflect.Int64:
fn.f = (*decFnInfo).kInt64
case reflect.Int32:
fn.f = (*decFnInfo).kInt32
case reflect.Int8:
fn.f = (*decFnInfo).kInt8
case reflect.Int16:
fn.f = (*decFnInfo).kInt16
case reflect.Float32:
fn.f = (*decFnInfo).kFloat32
case reflect.Float64:
fn.f = (*decFnInfo).kFloat64
case reflect.Uint8:
fn.f = (*decFnInfo).kUint8
case reflect.Uint64:
fn.f = (*decFnInfo).kUint64
case reflect.Uint:
fn.f = (*decFnInfo).kUint
case reflect.Uint32:
fn.f = (*decFnInfo).kUint32
case reflect.Uint16:
fn.f = (*decFnInfo).kUint16
// case reflect.Ptr:
// fn.f = (*decFnInfo).kPtr
case reflect.Uintptr:
fn.f = (*decFnInfo).kUintptr
case reflect.Interface:
fn.f = (*decFnInfo).kInterface
case reflect.Struct:
fn.f = (*decFnInfo).kStruct
case reflect.Chan:
fi.seq = seqTypeChan
fn.f = (*decFnInfo).kSlice
case reflect.Slice:
fi.seq = seqTypeSlice
fn.f = (*decFnInfo).kSlice
case reflect.Array:
fi.seq = seqTypeArray
fn.f = (*decFnInfo).kArray
case reflect.Map:
fn.f = (*decFnInfo).kMap
default:
fn.f = (*decFnInfo).kErr
}
}
}
return
}
func (d *Decoder) structFieldNotFound(index int, rvkencname string) {
if d.h.ErrorIfNoField {
if index >= 0 {
d.errorf("no matching struct field found when decoding stream array at index %v", index)
return
} else if rvkencname != "" {
d.errorf("no matching struct field found when decoding stream map with key %s", rvkencname)
return
}
}
d.swallow()
}
func (d *Decoder) arrayCannotExpand(sliceLen, streamLen int) {
if d.h.ErrorIfNoArrayExpand {
d.errorf("cannot expand array len during decode from %v to %v", sliceLen, streamLen)
}
}
func (d *Decoder) chkPtrValue(rv reflect.Value) {
// We can only decode into a non-nil pointer
if rv.Kind() == reflect.Ptr && !rv.IsNil() {
return
}
if !rv.IsValid() {
d.error(cannotDecodeIntoNilErr)
return
}
if !rv.CanInterface() {
d.errorf("cannot decode into a value without an interface: %v", rv)
return
}
rvi := rv.Interface()
d.errorf("cannot decode into non-pointer or nil pointer. Got: %v, %T, %v", rv.Kind(), rvi, rvi)
}
func (d *Decoder) error(err error) {
panic(err)
}
func (d *Decoder) errorf(format string, params ...interface{}) {
params2 := make([]interface{}, len(params)+1)
params2[0] = d.r.numread()
copy(params2[1:], params)
err := fmt.Errorf("[pos %d]: "+format, params2...)
panic(err)
}
func (d *Decoder) string(v []byte) (s string) {
if d.is != nil {
s, ok := d.is[string(v)] // no allocation here.
if !ok {
s = string(v)
d.is[s] = s
}
return s
}
return string(v) // don't return stringView, as we need a real string here.
}
func (d *Decoder) intern(s string) {
if d.is != nil {
d.is[s] = s
}
}
// --------------------------------------------------
// decSliceHelper assists when decoding into a slice, from a map or an array in the stream.
// A slice can be set from a map or array in stream. This supports the MapBySlice interface.
type decSliceHelper struct {
dd decDriver
ct valueType
}
func (d *Decoder) decSliceHelperStart() (x decSliceHelper, clen int) {
x.dd = d.d
if x.dd.IsContainerType(valueTypeArray) {
x.ct = valueTypeArray
clen = x.dd.ReadArrayStart()
} else if x.dd.IsContainerType(valueTypeMap) {
x.ct = valueTypeMap
clen = x.dd.ReadMapStart() * 2
} else {
d.errorf("only encoded map or array can be decoded into a slice")
}
return
}
func (x decSliceHelper) End() {
x.dd.ReadEnd()
}
func decByteSlice(r decReader, clen int, bs []byte) (bsOut []byte) {
if clen == 0 {
return zeroByteSlice
}
if len(bs) == clen {
bsOut = bs
} else if cap(bs) >= clen {
bsOut = bs[:clen]
} else {
bsOut = make([]byte, clen)
}
r.readb(bsOut)
return
}
func detachZeroCopyBytes(isBytesReader bool, dest []byte, in []byte) (out []byte) {
if xlen := len(in); xlen > 0 {
if isBytesReader || xlen <= scratchByteArrayLen {
if cap(dest) >= xlen {
out = dest[:xlen]
} else {
out = make([]byte, xlen)
}
copy(out, in)
return
}
}
return in
}
// decInferLen will infer a sensible length, given the following:
// - clen: length wanted.
// - maxlen: max length to be returned.
// if <= 0, it is unset, and we infer it based on the unit size
// - unit: number of bytes for each element of the collection
func decInferLen(clen, maxlen, unit int) (rvlen int, truncated bool) {
// handle when maxlen is not set i.e. <= 0
if clen <= 0 {
return
}
if maxlen <= 0 {
// no maxlen defined. Use maximum of 256K memory, with a floor of 4K items.
// maxlen = 256 * 1024 / unit
// if maxlen < (4 * 1024) {
// maxlen = 4 * 1024
// }
if unit < (256 / 4) {
maxlen = 256 * 1024 / unit
} else {
maxlen = 4 * 1024
}
}
if clen > maxlen {
rvlen = maxlen
truncated = true
} else {
rvlen = clen
}
return
// if clen <= 0 {
// rvlen = 0
// } else if maxlen > 0 && clen > maxlen {
// rvlen = maxlen
// truncated = true
// } else {
// rvlen = clen
// }
// return
}
// // implement overall decReader wrapping both, for possible use inline:
// type decReaderT struct {
// bytes bool
// rb *bytesDecReader
// ri *ioDecReader
// }
//
// // implement *Decoder as a decReader.
// // Using decReaderT (defined just above) caused performance degradation
// // possibly because of constant copying the value,
// // and some value->interface conversion causing allocation.
// func (d *Decoder) unreadn1() {
// if d.bytes {
// d.rb.unreadn1()
// } else {
// d.ri.unreadn1()
// }
// }
// ... for other methods of decReader.
// Testing showed that performance improvement was negligible.
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