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/goHackTools/vendor/golang.org/x/crypto/ssh
    
    the code of the file until where you have to start completion: // Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by 
    
func (b *buffer) Read(buf []byte) (n int, err error) {
	b.Cond.L.Lock()
	defer b.Cond.L.Unlock()

	for len(buf) > 0 {
		// if there is data in b.head, copy it
		if len(b.head.buf) > 0 {
			r := copy(buf, b.head.buf)
			buf, b.head.buf = buf[r:], b.head.buf[r:]
			n += r
			continue
		}
		// if there is a next buffer, make it the head
		if len(b.head.buf) == 0 && b.head != b.tail {
			b.head = b.head.next
			continue
		}

		// if at least one byte has been copied, return
		if n > 0 {
			break
		}

		// if nothing was read, and there is nothing outstanding
		// check to see if the buffer is closed.
		if b.closed {
			err = io.EOF
			break
		}
		// out of buffers, wait for producer
		b.Cond.Wait()
	}
	return
}