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gob: decode into nil, this time for sure.

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Yesterday's change was too simple-minded and failed if an
interface value was being discarded.  We need to parse the
data stream and remember any type information that arrives.

Also fix a minor bug when ignoring an interface: toss only what
we know about, not everything.

R=rsc
CC=golang-dev
https://golang.org/cl/4179045
This commit is contained in:
Rob Pike 2011-02-14 10:17:30 -08:00
parent 1723fbe13e
commit 1778f50da3
3 changed files with 113 additions and 54 deletions
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50
src/pkg/gob/decode.go
View file

@ -481,6 +481,19 @@ func (dec *Decoder) ignoreStruct(engine *decEngine) (err os.Error) {
return nil
}
func (dec *Decoder) ignoreSingle(engine *decEngine) (err os.Error) {
defer catchError(&err)
state := newDecodeState(dec, &dec.buf)
state.fieldnum = singletonField
delta := int(state.decodeUint())
if delta != 0 {
errorf("gob decode: corrupted data: non-zero delta for singleton")
}
instr := &engine.instr[singletonField]
instr.op(instr, state, unsafe.Pointer(nil))
return nil
}
func (dec *Decoder) decodeArrayHelper(state *decodeState, p uintptr, elemOp decOp, elemWid uintptr, length, elemIndir int, ovfl os.ErrorString) {
instr := &decInstr{elemOp, 0, elemIndir, 0, ovfl}
for i := 0; i < length; i++ {
@ -653,8 +666,8 @@ func (dec *Decoder) ignoreInterface(state *decodeState) {
if id < 0 {
error(dec.err)
}
// At this point, the decoder buffer contains the value. Just toss it.
state.b.Reset()
// At this point, the decoder buffer contains a delimited value. Just toss it.
state.b.Next(int(state.decodeUint()))
}
// Index by Go types.
@ -901,6 +914,16 @@ func (dec *Decoder) compileSingle(remoteId typeId, rt reflect.Type) (engine *dec
return
}
func (dec *Decoder) compileIgnoreSingle(remoteId typeId) (engine *decEngine, err os.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, 0, 0, ovfl}
engine.numInstr = 1
return
}
// Is this an exported - upper case - name?
func isExported(name string) bool {
rune, _ := utf8.DecodeRuneInString(name)
@ -984,7 +1007,12 @@ func (dec *Decoder) getIgnoreEnginePtr(wireId typeId) (enginePtr **decEngine, er
// To handle recursive types, mark this engine as underway before compiling.
enginePtr = new(*decEngine)
dec.ignorerCache[wireId] = enginePtr
*enginePtr, err = dec.compileDec(wireId, emptyStructType)
wire := dec.wireType[wireId]
if wire != nil && wire.StructT != nil {
*enginePtr, err = dec.compileDec(wireId, emptyStructType)
} else {
*enginePtr, err = dec.compileIgnoreSingle(wireId)
}
if err != nil {
dec.ignorerCache[wireId] = nil, false
}
@ -993,6 +1021,10 @@ func (dec *Decoder) getIgnoreEnginePtr(wireId typeId) (enginePtr **decEngine, er
}
func (dec *Decoder) decodeValue(wireId typeId, val reflect.Value) os.Error {
// If the value is nil, it means we should just ignore this item.
if val == nil {
return dec.decodeIgnoredValue(wireId)
}
// Dereference down to the underlying struct type.
rt, indir := indirect(val.Type())
enginePtr, err := dec.getDecEnginePtr(wireId, rt)
@ -1010,6 +1042,18 @@ func (dec *Decoder) decodeValue(wireId typeId, val reflect.Value) os.Error {
return dec.decodeSingle(engine, rt, uintptr(val.Addr()), indir)
}
func (dec *Decoder) decodeIgnoredValue(wireId typeId) os.Error {
enginePtr, err := dec.getIgnoreEnginePtr(wireId)
if err != nil {
return err
}
wire := dec.wireType[wireId]
if wire != nil && wire.StructT != nil {
return dec.ignoreStruct(*enginePtr)
}
return dec.ignoreSingle(*enginePtr)
}
func init() {
var iop, uop decOp
switch reflect.Typeof(int(0)).Bits() {