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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) *RingBuffer {
ringBuf := RingBuffer{
slice: slice,
}
return &ringBuf
}
// Write method inserts the elements in a byte slice, and returns the number of bytes written along with any error.
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
}
// Read copies the data on the ring buffer into the byte slice provided to the method.
// Returns the read count along with any error encountered while reading.
func (r *RingBuffer) Read(p []byte) (int, error) {
// readCount keeps track of the number of bytes read
var readCount int
for j := 0; j < len(p); j++ {
// if ring buffer is empty or completely read
// return EOF error.
if r.size == 0 {
return readCount, io.EOF
}
if r.start == len(r.slice) {
r.start = 0
}
p[j] = r.slice[r.start]
readCount++
// increment the start pointer for ring buffer
r.start++
// decrement the size of ring buffer
r.size--
}
return readCount, nil
}
// Len returns the number of unread bytes in the buffer.
func (r *RingBuffer) Len() int {
return r.size
}
// Bytes returns a copy of the RingBuffer's bytes.
func (r RingBuffer) Bytes() []byte {
var b bytes.Buffer
io.Copy(&b, &r)
return b.Bytes()
}
// Reset resets the ring buffer.
func (r *RingBuffer) Reset() {
*r = RingBuffer{
slice: r.slice,
}
}
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