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: ringbuffer.go
    path of file: ./repos/sliver/vendor/github.com/aws/smithy-go/io
    
    the code of the file until where you have to start completion: package io

import (
	"bytes"
	"io"
)

// RingBuffer struct satisfies io.ReadWrite interface.
//
// ReadBuffer is a revolving buffer data structure, which can be used to store snapshots of data in a
// revolving window.
type RingBuffer struct {
	slice []byte
	start int
	end   int
	size  int
}

// NewRingBuffer method takes in a byte slice as an input and returns a RingBuffer.
func NewRingBuffer(slice []byte) *Ring
    
func (r *RingBuffer) Write(p []byte) (int, error) {
	for _, b := range p {
		// check if end points to invalid index, we need to circle back
		if r.end == len(r.slice) {
			r.end = 0
		}
		// check if start points to invalid index, we need to circle back
		if r.start == len(r.slice) {
			r.start = 0
		}
		// if ring buffer is filled, increment the start index
		if r.size == len(r.slice) {
			r.size--
			r.start++
		}

		r.slice[r.end] = b
		r.end++
		r.size++
	}
	return len(p), nil
}