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  1. // Copyright 2013 Matt T. Proud
  2. //
  3. // Licensed under the Apache License, Version 2.0 (the "License");
  4. // you may not use this file except in compliance with the License.
  5. // You may obtain a copy of the License at
  6. //
  7. // http://www.apache.org/licenses/LICENSE-2.0
  8. //
  9. // Unless required by applicable law or agreed to in writing, software
  10. // distributed under the License is distributed on an "AS IS" BASIS,
  11. // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12. // See the License for the specific language governing permissions and
  13. // limitations under the License.
  14. package pbutil
  15. import (
  16. "encoding/binary"
  17. "io"
  18. "github.com/golang/protobuf/proto"
  19. )
  20. // WriteDelimited encodes and dumps a message to the provided writer prefixed
  21. // with a 32-bit varint indicating the length of the encoded message, producing
  22. // a length-delimited record stream, which can be used to chain together
  23. // encoded messages of the same type together in a file. It returns the total
  24. // number of bytes written and any applicable error. This is roughly
  25. // equivalent to the companion Java API's MessageLite#writeDelimitedTo.
  26. func WriteDelimited(w io.Writer, m proto.Message) (n int, err error) {
  27. buffer, err := proto.Marshal(m)
  28. if err != nil {
  29. return 0, err
  30. }
  31. var buf [binary.MaxVarintLen32]byte
  32. encodedLength := binary.PutUvarint(buf[:], uint64(len(buffer)))
  33. sync, err := w.Write(buf[:encodedLength])
  34. if err != nil {
  35. return sync, err
  36. }
  37. n, err = w.Write(buffer)
  38. return n + sync, err
  39. }
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