Simple queue implementation

queue.go

package types

// Note: this queue does not shrink the underlying buffer.                                                                                                               
type queue struct {
        buf  [][4]int // change to the element data type that you need                                                                                                   
        head int
        tail int
}

func (q *queue) extend(need int) {
        if need-(len(q.buf)-q.head) > 0 {
                if need-len(q.buf) <= 0 {
                        copy(q.buf, q.buf[q.head:q.tail])
			q.tail = q.tail - q.head
                        q.head = 0
                        return
                }

                newSize := len(q.buf) * 2
                if newSize == 0 {
	                newSize = 100
	        }
                newBuf := make([][4]int, newSize)
                copy(newBuf, q.buf[q.head:q.tail])
                q.buf = newBuf
		q.tail = q.tail - q.head
                q.head = 0
        }
}

func (q *queue) push(p [4]int) {
        q.extend(q.tail + 1)
        q.buf[q.tail] = p
        q.tail++
}

func (q *queue) pop() [4]int {
        r := q.buf[q.head]
        q.head++
        return r
}

func (q *queue) size() int {
        return q.tail - q.head
}


// put the following into queue_test.go
package types

import (
        "testing"

        "github.com/stretchr/testify/assert"
)

func TestQueue(t *testing.T) {
        const total = 1000
        q := &queue{}
        for i := 0; i < total; i++ {
                q.push([4]int{i, i, i, i})
                assert.Equal(t, i+1, q.size())
        }

	for i := 0; i < total; i++ {
                v := q.pop()
                assert.Equal(t, [4]int{i, i, i, i}, v)
                assert.Equal(t, total-1-i, q.size())
        }
}