You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: buffer.go
    path of file: ./repos/kubernetes/vendor/github.com/soheilhy/cmux
    
    the code of the file until where you have to start completion: // Copyright 2016 The CMux Authors. All rights reserved.
//
// 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 CONDITIO
    
func (s *bufferedReader) Read(p []byte) (int, error) {
	if s.bufferSize > s.bufferRead {
		// If we have already read something from the buffer before, we return the
		// same data and the last error if any. We need to immediately return,
		// otherwise we may block for ever, if we try to be smart and call
		// source.Read() seeking a little bit of more data.
		bn := copy(p, s.buffer.Bytes()[s.bufferRead:s.bufferSize])
		s.bufferRead += bn
		return bn, s.lastErr
	} else if !s.sniffing && s.buffer.Cap() != 0 {
		// We don't need the buffer anymore.
		// Reset it to release the internal slice.
		s.buffer = bytes.Buffer{}
	}

	// If there is nothing more to return in the sniffed buffer, read from the
	// source.
	sn, sErr := s.source.Read(p)
	if sn > 0 && s.sniffing {
		s.lastErr = sErr
		if wn, wErr := s.buffer.Write(p[:sn]); wErr != nil {
			return wn, wErr
		}
	}
	return sn, sErr
}