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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:23:18 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:23:18 +0000
commit43a123c1ae6613b3efeed291fa552ecd909d3acf (patch)
treefd92518b7024bc74031f78a1cf9e454b65e73665 /src/encoding/gob/encoder.go
parentInitial commit. (diff)
downloadgolang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz
golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/encoding/gob/encoder.go')
-rw-r--r--src/encoding/gob/encoder.go258
1 files changed, 258 insertions, 0 deletions
diff --git a/src/encoding/gob/encoder.go b/src/encoding/gob/encoder.go
new file mode 100644
index 0000000..5a80e6c
--- /dev/null
+++ b/src/encoding/gob/encoder.go
@@ -0,0 +1,258 @@
+// 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 (
+ "errors"
+ "io"
+ "reflect"
+ "sync"
+)
+
+// An Encoder manages the transmission of type and data information to the
+// other side of a connection. It is safe for concurrent use by multiple
+// goroutines.
+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 encBuffer // 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(encBuffer))
+ 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 *encBuffer) {
+ // 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
+ // Length cannot be bigger than the decoder can handle.
+ if messageLen >= tooBig {
+ enc.setError(errors.New("gob: encoder: message too big"))
+ return
+ }
+ // 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
+ }
+ info, err := getTypeInfo(ut)
+ 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.
+// Passing a nil pointer to Encoder will panic, as they cannot be transmitted by gob.
+func (enc *Encoder) Encode(e any) 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 {
+ info, err := getTypeInfo(ut)
+ 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.
+// Passing a nil pointer to EncodeValue will panic, as they cannot be transmitted by gob.
+func (enc *Encoder) EncodeValue(value reflect.Value) error {
+ if value.Kind() == reflect.Invalid {
+ return errors.New("gob: cannot encode nil value")
+ }
+ if value.Kind() == reflect.Pointer && 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
+}