type Reader interface {
	// ReadOnReady waits for data to arrive, fetches a buffer, and performs a
	// read. When the underlying IO is readable, it allocates a buffer of size
	// bufSize from the pool and reads up to bufSize bytes into the buffer.
	//
	// It returns a pointer to the buffer so it can be returned to the pool
	// later, the number of bytes read, and an error.
	//
	// Callers should always process the n > 0 bytes returned before considering
	// the error. Doing so correctly handles I/O errors that happen after
	// reading some bytes, as well as both of the allowed EOF behaviors.
	ReadOnReady(bufSize int, pool mem.BufferPool) (b *[]byte, n int, err error)
}