diff options
Diffstat (limited to 'vendor/github.com/matttproud/golang_protobuf_extensions/pbutil/decode.go')
-rw-r--r-- | vendor/github.com/matttproud/golang_protobuf_extensions/pbutil/decode.go | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/vendor/github.com/matttproud/golang_protobuf_extensions/pbutil/decode.go b/vendor/github.com/matttproud/golang_protobuf_extensions/pbutil/decode.go new file mode 100644 index 000000000..258c0636a --- /dev/null +++ b/vendor/github.com/matttproud/golang_protobuf_extensions/pbutil/decode.go @@ -0,0 +1,75 @@ +// Copyright 2013 Matt T. Proud +// +// Licensed under the Apache License, Version 2.0 (the "License"); +// you may not use this file except in compliance with the License. +// You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, software +// distributed under the License is distributed on an "AS IS" BASIS, +// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +// See the License for the specific language governing permissions and +// limitations under the License. + +package pbutil + +import ( + "encoding/binary" + "errors" + "io" + + "github.com/golang/protobuf/proto" +) + +var errInvalidVarint = errors.New("invalid varint32 encountered") + +// ReadDelimited decodes a message from the provided length-delimited stream, +// where the length is encoded as 32-bit varint prefix to the message body. +// It returns the total number of bytes read and any applicable error. This is +// roughly equivalent to the companion Java API's +// MessageLite#parseDelimitedFrom. As per the reader contract, this function +// calls r.Read repeatedly as required until exactly one message including its +// prefix is read and decoded (or an error has occurred). The function never +// reads more bytes from the stream than required. The function never returns +// an error if a message has been read and decoded correctly, even if the end +// of the stream has been reached in doing so. In that case, any subsequent +// calls return (0, io.EOF). +func ReadDelimited(r io.Reader, m proto.Message) (n int, err error) { + // Per AbstractParser#parsePartialDelimitedFrom with + // CodedInputStream#readRawVarint32. + var headerBuf [binary.MaxVarintLen32]byte + var bytesRead, varIntBytes int + var messageLength uint64 + for varIntBytes == 0 { // i.e. no varint has been decoded yet. + if bytesRead >= len(headerBuf) { + return bytesRead, errInvalidVarint + } + // We have to read byte by byte here to avoid reading more bytes + // than required. Each read byte is appended to what we have + // read before. + newBytesRead, err := r.Read(headerBuf[bytesRead : bytesRead+1]) + if newBytesRead == 0 { + if err != nil { + return bytesRead, err + } + // A Reader should not return (0, nil), but if it does, + // it should be treated as no-op (according to the + // Reader contract). So let's go on... + continue + } + bytesRead += newBytesRead + // Now present everything read so far to the varint decoder and + // see if a varint can be decoded already. + messageLength, varIntBytes = proto.DecodeVarint(headerBuf[:bytesRead]) + } + + messageBuf := make([]byte, messageLength) + newBytesRead, err := io.ReadFull(r, messageBuf) + bytesRead += newBytesRead + if err != nil { + return bytesRead, err + } + + return bytesRead, proto.Unmarshal(messageBuf, m) +} |