40 lines
875 B
JavaScript
40 lines
875 B
JavaScript
module.exports = class FixedFIFO {
|
|
constructor (hwm) {
|
|
if (!(hwm > 0) || ((hwm - 1) & hwm) !== 0) throw new Error('Max size for a FixedFIFO should be a power of two')
|
|
this.buffer = new Array(hwm)
|
|
this.mask = hwm - 1
|
|
this.top = 0
|
|
this.btm = 0
|
|
this.next = null
|
|
}
|
|
|
|
clear () {
|
|
this.top = this.btm = 0
|
|
this.next = null
|
|
this.buffer.fill(undefined)
|
|
}
|
|
|
|
push (data) {
|
|
if (this.buffer[this.top] !== undefined) return false
|
|
this.buffer[this.top] = data
|
|
this.top = (this.top + 1) & this.mask
|
|
return true
|
|
}
|
|
|
|
shift () {
|
|
const last = this.buffer[this.btm]
|
|
if (last === undefined) return undefined
|
|
this.buffer[this.btm] = undefined
|
|
this.btm = (this.btm + 1) & this.mask
|
|
return last
|
|
}
|
|
|
|
peek () {
|
|
return this.buffer[this.btm]
|
|
}
|
|
|
|
isEmpty () {
|
|
return this.buffer[this.btm] === undefined
|
|
}
|
|
}
|