Method Read

pkg/signer/request-signature-streaming.go:431–491

Read - this method performs chunk upload signature providing a io.Reader interface.

(buf []byte)

// Read - this method performs chunk upload signature providing a
// io.Reader interface.
func (s *StreamingReader) Read(buf []byte) (int, error) {
	switch {
	// After the last chunk is read from underlying reader, we
	// never re-fill s.buf.
	case s.done:

	// s.buf will be (re-)filled with next chunk when has lesser
	// bytes than asked for.
	case s.buf.Len() < len(buf):
		s.chunkBufLen = 0
		for {
			n1, err := s.baseReadCloser.Read(s.chunkBuf[s.chunkBufLen:])
			// Usually we validate `err` first, but in this case
			// we are validating n > 0 for the following reasons.
			//
			// 1. n > 0, err is one of io.EOF, nil (near end of stream)
			// A Reader returning a non-zero number of bytes at the end
			// of the input stream may return either err == EOF or err == nil
			//
			// 2. n == 0, err is io.EOF (actual end of stream)
			//
			// Callers should always process the n > 0 bytes returned
			// before considering the error err.
			if n1 > 0 {
				s.chunkBufLen += n1
				s.bytesRead += int64(n1)

				if s.chunkBufLen == payloadChunkSize ||
					(s.chunkNum == s.totalChunks-1 &&
						s.chunkBufLen == s.lastChunkSize) {
					// Sign the chunk and write it to s.buf.
					s.signChunk(s.chunkBufLen, true)
					break
				}
			}
			if err != nil {
				if err == io.EOF {
					// No more data left in baseReader - last chunk.
					// Done reading the last chunk from baseReader.
					s.done = true

					// bytes read from baseReader different than
					// content length provided.
					if s.bytesRead != s.contentLen {
						return 0, fmt.Errorf("http: ContentLength=%d with Body length %d", s.contentLen, s.bytesRead)
					}

					// Sign the chunk and write it to s.buf.
					s.signChunk(0, len(s.trailer) == 0)
					if len(s.trailer) > 0 {
						// Trailer must be set now.
						s.addSignedTrailer(s.trailer)
					}
					break
				}
				return 0, err
			}
		}