https://vc64web.github.io/js/ringbuffer.js

1//ported from Emulator/Utilities/RingBuffer.h and speed optimized for Javascript mithrendal
2class RingBuffer {
3    constructor(capacity) {
4        this.capacity = capacity+1;
5        this.capacity_usable = capacity;
6        this.r = 0;
7        this.w = 0;
8        this.elements = new ArrayBuffer(this.capacity);
9    }
10 
11    clear(){
12        this.r = 0;
13        this.w = 0;
14        for (let i = 0; i < this.capacity; i++) { this.elements[i] = null; }
15    }
16 
17    align(offset) {
18        this.w = (this.r + offset) % this.capacity;
19    }
20 
21    count() {
22        return (this.capacity + this.w - this.r) % this.capacity;
23    }
24    free()  { return this.capacity - this.count() - 1; }
25    fillLevel() { return this.count() / this.capacity; }
26    isEmpty()  { return this.r == this.w; }
27    isFull()  { return this.count() == this.capacity - 1; }
28 
29    begin()  { return this.r; }
30    end()  { return this.w; }
31    next(i) { return i < this.capacity - 1 ? i + 1 : 0; }
32    prev(i) { return i > 0 ? i - 1 : this.capacity - 1; }
33 
34    read()
35    {
36//        console.assert(!this.isEmpty(), "Ringbuffer.read() -> !isEmpty()");
37 
38        let oldr = this.r;
39        //this.r = this.next(this.r);
40        this.r = this.r < this.capacity_usable ? this.r + 1 : 0;
41        return this.elements[oldr];
42    }
43 
44    write(element)
45    {
46//        console.log("write "+element)
47//        console.assert(!this.isFull(), "Ringbuffer.write() -> !isFull()");
48 
49        this.elements[this.w] = element;
50        //this.w = this.next(this.w);
51        this.w = this.w < this.capacity_usable ? this.w + 1 : 0;
52    }
53  
54    skip()
55    {
56        this.r = this.next(this.r);
57    }
58   
59    skip(n)
60    {
61        this.r = (this.r + n) % this.capacity;
62    }
63   
64    current(offset)
65    {
66        return this.elements[(this.r + offset) % this.capacity];
67    }
68}
69