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Zeal Jagannatha
72
README.md
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72
README.md
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# ring
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--
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import "git.sky/shenzhen/ring"
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## Usage
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```go
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var DefaultCapacity int = 10
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```
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The DefaultCapacity of an uninitialized Ring buffer.
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Changing this value only affects ring buffers created after it is changed.
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#### type Ring
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```go
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type Ring struct {
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}
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```
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Type Ring implements a Circular Buffer. The default value of the Ring struct is
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a valid (empty) Ring buffer with capacity DefaultCapacify.
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#### func (Ring) Capacity
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```go
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func (r Ring) Capacity() int
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```
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Capacity returns the current capacity of the ring buffer.
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#### func (*Ring) Dequeue
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```go
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func (r *Ring) Dequeue() interface{}
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```
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Dequeue a value from the Ring buffer.
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Returns nil if the ring buffer is empty.
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#### func (*Ring) Enqueue
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```go
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func (r *Ring) Enqueue(i interface{})
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```
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Enqueue a value into the Ring buffer.
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#### func (*Ring) Peek
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```go
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func (r *Ring) Peek() interface{}
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```
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Read the value that Dequeue would have dequeued without actually dequeuing it.
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Returns nil if the ring buffer is empty.
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#### func (*Ring) SetCapacity
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```go
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func (r *Ring) SetCapacity(size int)
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```
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Set the maximum size of the ring buffer.
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#### func (*Ring) Values
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```go
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func (r *Ring) Values() []interface{}
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```
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Values returns a slice of all the values in the circular buffer without
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modifying them at all. The returned slice can be modified independently of the
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circular buffer. However, the values inside the slice are shared between the
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slice and circular buffer.
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141
ring.go
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141
ring.go
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package ring
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/*
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The DefaultCapacity of an uninitialized Ring buffer.
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Changing this value only affects ring buffers created after it is changed.
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*/
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var DefaultCapacity int = 10
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/*
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Type Ring implements a Circular Buffer.
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The default value of the Ring struct is a valid (empty) Ring buffer with capacity DefaultCapacify.
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*/
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type Ring struct {
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head int // the most recent value written
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tail int // the least recent value written
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buff []interface{}
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}
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/*
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Set the maximum size of the ring buffer.
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*/
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func (r *Ring) SetCapacity(size int) {
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r.checkInit()
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r.extend(size)
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}
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/*
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Capacity returns the current capacity of the ring buffer.
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*/
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func (r Ring) Capacity() int {
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return len(r.buff)
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}
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/*
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Enqueue a value into the Ring buffer.
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*/
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func (r *Ring) Enqueue(i interface{}) {
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r.checkInit()
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r.set(r.head+1, i)
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old := r.head
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r.head = r.mod(r.head+1)
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if old != -1 && r.head == r.tail {
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r.tail = r.mod(r.tail + 1)
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}
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}
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/*
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Dequeue a value from the Ring buffer.
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Returns nil if the ring buffer is empty.
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*/
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func (r *Ring) Dequeue() interface{} {
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r.checkInit()
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if r.head == -1 {
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return nil
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}
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v := r.get(r.tail)
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if r.tail == r.head {
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r.head = -1
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r.tail = 0
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} else {
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r.tail = r.mod(r.tail + 1)
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}
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return v
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}
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/*
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Read the value that Dequeue would have dequeued without actually dequeuing it.
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Returns nil if the ring buffer is empty.
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*/
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func (r *Ring) Peek() interface{} {
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r.checkInit()
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if r.head == -1 {
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return nil
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}
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return r.get(r.tail)
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}
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/*
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Values returns a slice of all the values in the circular buffer without modifying them at all.
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The returned slice can be modified independently of the circular buffer. However, the values inside the slice
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are shared between the slice and circular buffer.
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*/
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func (r *Ring) Values() []interface{} {
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if r.head == -1 {
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return []interface{}{}
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}
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arr := make([]interface{}, 0, r.Capacity())
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for i := 0; i < r.Capacity(); i++ {
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idx := r.mod(i+r.tail)
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arr = append(arr, r.get(idx))
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if idx == r.head {
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break
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}
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}
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return arr
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}
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/**
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*** Unexported methods beyond this point.
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**/
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// sets a value at the given unmodified index and returns the modified index of the value
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func (r *Ring) set(p int, v interface{}) {
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r.buff[r.mod(p)] = v
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}
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// gets a value based at a given unmodified index
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func (r *Ring) get(p int) interface{} {
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return r.buff[r.mod(p)]
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}
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// returns the modified index of an unmodified index
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func (r *Ring) mod(p int) int {
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return p % len(r.buff)
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}
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func (r *Ring) checkInit() {
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if r.buff == nil {
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r.buff = make([]interface{}, DefaultCapacity)
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for i := range r.buff {
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r.buff[i] = nil
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}
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r.head, r.tail = -1, 0
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}
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}
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func (r *Ring) extend(size int) {
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if size == len(r.buff) {
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return
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} else if size < len(r.buff) {
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r.buff = r.buff[0:size]
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}
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newb := make([]interface{}, size-len(r.buff))
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for i := range newb {
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newb[i] = nil
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}
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r.buff = append(r.buff, newb...)
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}
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116
ring_test.go
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116
ring_test.go
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@@ -0,0 +1,116 @@
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package ring
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import (
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// "fmt"
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"testing"
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)
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func TestSetsSize(t *testing.T) {
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r := &Ring{}
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r.SetCapacity(10)
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if r.Capacity() != 10 {
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t.Fatal("Size of ring was not 10", r.Capacity())
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}
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}
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func TestSavesSomeData(t *testing.T) {
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r := Ring{}
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r.SetCapacity(10)
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for i := 0; i < 7; i++ {
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r.Enqueue(i)
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}
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for i := 0; i < 7; i++ {
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x := r.Dequeue()
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if x != i {
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t.Fatal("Unexpected response", x, "wanted", i)
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}
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}
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}
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func TestReusesBuffer(t *testing.T) {
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r := Ring{}
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r.SetCapacity(10)
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for i := 0; i < 7; i++ {
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r.Enqueue(i)
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}
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for i := 0; i < 7; i++ {
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r.Dequeue()
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}
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for i := 7; i < 14; i++ {
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r.Enqueue(i)
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}
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for i := 7; i < 14; i++ {
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x := r.Dequeue()
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if x != i {
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t.Fatal("Unexpected response", x, "wanted", i)
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}
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}
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}
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func TestOverflowsBuffer(t *testing.T) {
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r := Ring{}
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r.SetCapacity(10)
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for i := 0; i < 20; i++ {
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r.Enqueue(i)
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}
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for i := 10; i < 20; i++ {
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x := r.Dequeue()
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if x != i {
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t.Fatal("Unexpected response", x, "wanted", i)
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}
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}
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}
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func TestPartiallyOverflows(t *testing.T) {
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r := Ring{}
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r.SetCapacity(10)
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for i := 0; i < 15; i++ {
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r.Enqueue(i)
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}
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for i := 5; i < 15; i++ {
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x := r.Dequeue()
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if x != i {
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t.Fatal("Unexpected response", x, "wanted", i)
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}
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}
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}
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func TestPeeks(t *testing.T) {
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r := Ring{}
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r.SetCapacity(10)
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for i := 0; i < 10; i++ {
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r.Enqueue(i)
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}
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for i := 0; i < 10; i++ {
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r.Peek()
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r.Peek()
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x1 := r.Peek()
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x := r.Dequeue()
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if x != i {
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t.Fatal("Unexpected response", x, "wanted", i)
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}
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if x1 != x {
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t.Fatal("Unexpected response", x1, "wanted", x)
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}
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}
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}
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func TestConstructsArr(t *testing.T) {
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r := Ring{}
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r.SetCapacity(10)
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v := r.Values()
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if len(v) != 0 {
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t.Fatal("Unexpected values", v, "wanted len of", 0)
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}
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for i := 1; i < 21; i++ {
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r.Enqueue(i)
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l := i
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if l > 10 {
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l = 10
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}
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v = r.Values()
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if len(v) != l {
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t.Fatal("Unexpected values", v, "wanted len of", l, "index", i)
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}
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}
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}
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