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Diffstat (limited to 'src/pkg/encoding/gob/encoder.go')
-rw-r--r-- | src/pkg/encoding/gob/encoder.go | 253 |
1 files changed, 0 insertions, 253 deletions
diff --git a/src/pkg/encoding/gob/encoder.go b/src/pkg/encoding/gob/encoder.go deleted file mode 100644 index a3301c3bd..000000000 --- a/src/pkg/encoding/gob/encoder.go +++ /dev/null @@ -1,253 +0,0 @@ -// Copyright 2009 The Go Authors. All rights reserved. -// Use of this source code is governed by a BSD-style -// license that can be found in the LICENSE file. - -package gob - -import ( - "bytes" - "io" - "reflect" - "sync" -) - -// An Encoder manages the transmission of type and data information to the -// other side of a connection. -type Encoder struct { - mutex sync.Mutex // each item must be sent atomically - w []io.Writer // where to send the data - sent map[reflect.Type]typeId // which types we've already sent - countState *encoderState // stage for writing counts - freeList *encoderState // list of free encoderStates; avoids reallocation - byteBuf bytes.Buffer // buffer for top-level encoderState - err error -} - -// Before we encode a message, we reserve space at the head of the -// buffer in which to encode its length. This means we can use the -// buffer to assemble the message without another allocation. -const maxLength = 9 // Maximum size of an encoded length. -var spaceForLength = make([]byte, maxLength) - -// NewEncoder returns a new encoder that will transmit on the io.Writer. -func NewEncoder(w io.Writer) *Encoder { - enc := new(Encoder) - enc.w = []io.Writer{w} - enc.sent = make(map[reflect.Type]typeId) - enc.countState = enc.newEncoderState(new(bytes.Buffer)) - return enc -} - -// writer() returns the innermost writer the encoder is using -func (enc *Encoder) writer() io.Writer { - return enc.w[len(enc.w)-1] -} - -// pushWriter adds a writer to the encoder. -func (enc *Encoder) pushWriter(w io.Writer) { - enc.w = append(enc.w, w) -} - -// popWriter pops the innermost writer. -func (enc *Encoder) popWriter() { - enc.w = enc.w[0 : len(enc.w)-1] -} - -func (enc *Encoder) setError(err error) { - if enc.err == nil { // remember the first. - enc.err = err - } -} - -// writeMessage sends the data item preceded by a unsigned count of its length. -func (enc *Encoder) writeMessage(w io.Writer, b *bytes.Buffer) { - // Space has been reserved for the length at the head of the message. - // This is a little dirty: we grab the slice from the bytes.Buffer and massage - // it by hand. - message := b.Bytes() - messageLen := len(message) - maxLength - // Encode the length. - enc.countState.b.Reset() - enc.countState.encodeUint(uint64(messageLen)) - // Copy the length to be a prefix of the message. - offset := maxLength - enc.countState.b.Len() - copy(message[offset:], enc.countState.b.Bytes()) - // Write the data. - _, err := w.Write(message[offset:]) - // Drain the buffer and restore the space at the front for the count of the next message. - b.Reset() - b.Write(spaceForLength) - if err != nil { - enc.setError(err) - } -} - -// sendActualType sends the requested type, without further investigation, unless -// it's been sent before. -func (enc *Encoder) sendActualType(w io.Writer, state *encoderState, ut *userTypeInfo, actual reflect.Type) (sent bool) { - if _, alreadySent := enc.sent[actual]; alreadySent { - return false - } - typeLock.Lock() - info, err := getTypeInfo(ut) - typeLock.Unlock() - if err != nil { - enc.setError(err) - return - } - // Send the pair (-id, type) - // Id: - state.encodeInt(-int64(info.id)) - // Type: - enc.encode(state.b, reflect.ValueOf(info.wire), wireTypeUserInfo) - enc.writeMessage(w, state.b) - if enc.err != nil { - return - } - - // Remember we've sent this type, both what the user gave us and the base type. - enc.sent[ut.base] = info.id - if ut.user != ut.base { - enc.sent[ut.user] = info.id - } - // Now send the inner types - switch st := actual; st.Kind() { - case reflect.Struct: - for i := 0; i < st.NumField(); i++ { - if isExported(st.Field(i).Name) { - enc.sendType(w, state, st.Field(i).Type) - } - } - case reflect.Array, reflect.Slice: - enc.sendType(w, state, st.Elem()) - case reflect.Map: - enc.sendType(w, state, st.Key()) - enc.sendType(w, state, st.Elem()) - } - return true -} - -// sendType sends the type info to the other side, if necessary. -func (enc *Encoder) sendType(w io.Writer, state *encoderState, origt reflect.Type) (sent bool) { - ut := userType(origt) - if ut.externalEnc != 0 { - // The rules are different: regardless of the underlying type's representation, - // we need to tell the other side that the base type is a GobEncoder. - return enc.sendActualType(w, state, ut, ut.base) - } - - // It's a concrete value, so drill down to the base type. - switch rt := ut.base; rt.Kind() { - default: - // Basic types and interfaces do not need to be described. - return - case reflect.Slice: - // If it's []uint8, don't send; it's considered basic. - if rt.Elem().Kind() == reflect.Uint8 { - return - } - // Otherwise we do send. - break - case reflect.Array: - // arrays must be sent so we know their lengths and element types. - break - case reflect.Map: - // maps must be sent so we know their lengths and key/value types. - break - case reflect.Struct: - // structs must be sent so we know their fields. - break - case reflect.Chan, reflect.Func: - // If we get here, it's a field of a struct; ignore it. - return - } - - return enc.sendActualType(w, state, ut, ut.base) -} - -// Encode transmits the data item represented by the empty interface value, -// guaranteeing that all necessary type information has been transmitted first. -func (enc *Encoder) Encode(e interface{}) error { - return enc.EncodeValue(reflect.ValueOf(e)) -} - -// sendTypeDescriptor makes sure the remote side knows about this type. -// It will send a descriptor if this is the first time the type has been -// sent. -func (enc *Encoder) sendTypeDescriptor(w io.Writer, state *encoderState, ut *userTypeInfo) { - // Make sure the type is known to the other side. - // First, have we already sent this type? - rt := ut.base - if ut.externalEnc != 0 { - rt = ut.user - } - if _, alreadySent := enc.sent[rt]; !alreadySent { - // No, so send it. - sent := enc.sendType(w, state, rt) - if enc.err != nil { - return - } - // If the type info has still not been transmitted, it means we have - // a singleton basic type (int, []byte etc.) at top level. We don't - // need to send the type info but we do need to update enc.sent. - if !sent { - typeLock.Lock() - info, err := getTypeInfo(ut) - typeLock.Unlock() - if err != nil { - enc.setError(err) - return - } - enc.sent[rt] = info.id - } - } -} - -// sendTypeId sends the id, which must have already been defined. -func (enc *Encoder) sendTypeId(state *encoderState, ut *userTypeInfo) { - // Identify the type of this top-level value. - state.encodeInt(int64(enc.sent[ut.base])) -} - -// EncodeValue transmits the data item represented by the reflection value, -// guaranteeing that all necessary type information has been transmitted first. -func (enc *Encoder) EncodeValue(value reflect.Value) error { - // Gobs contain values. They cannot represent nil pointers, which - // have no value to encode. - if value.Kind() == reflect.Ptr && value.IsNil() { - panic("gob: cannot encode nil pointer of type " + value.Type().String()) - } - - // Make sure we're single-threaded through here, so multiple - // goroutines can share an encoder. - enc.mutex.Lock() - defer enc.mutex.Unlock() - - // Remove any nested writers remaining due to previous errors. - enc.w = enc.w[0:1] - - ut, err := validUserType(value.Type()) - if err != nil { - return err - } - - enc.err = nil - enc.byteBuf.Reset() - enc.byteBuf.Write(spaceForLength) - state := enc.newEncoderState(&enc.byteBuf) - - enc.sendTypeDescriptor(enc.writer(), state, ut) - enc.sendTypeId(state, ut) - if enc.err != nil { - return enc.err - } - - // Encode the object. - enc.encode(state.b, value, ut) - if enc.err == nil { - enc.writeMessage(enc.writer(), state.b) - } - - enc.freeEncoderState(state) - return enc.err -} |