64 lines
2.4 KiB
JavaScript
64 lines
2.4 KiB
JavaScript
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// Recent known-pilot observations. Fixed memory; no audio or content retained.
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const CAPACITY = 1000;
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export class PilotWindow {
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constructor(windowMs) {
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if (!Number.isFinite(windowMs) || windowMs <= 0 || windowMs > 100) {
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throw new RangeError('pilot observation duration');
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}
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this.windowMs = windowMs;
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this.history = new Uint8Array(CAPACITY);
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this.next = 0;
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this.count = 0;
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this.lastEndMs = null;
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this.interruptions = 0;
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}
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interrupt() {
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this.next = 0;
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this.count = 0;
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this.lastEndMs = null;
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this.interruptions = Math.min(Number.MAX_SAFE_INTEGER, this.interruptions + 1);
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}
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observe(present, endMs) {
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if (typeof present !== 'boolean' || !Number.isFinite(endMs) || endMs < this.windowMs) {
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this.interrupt();
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return;
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}
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// The detector emits equal-sized, contiguous sample windows. Missing
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// callbacks are unknown coverage, not evidence of missing pilot PCM.
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if (this.lastEndMs !== null &&
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Math.abs(endMs - this.lastEndMs - this.windowMs) > 0.001) {
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this.interrupt();
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}
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this.history[this.next] = present ? 1 : 0;
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this.next = (this.next + 1) % CAPACITY;
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this.count = Math.min(CAPACITY, this.count + 1);
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this.lastEndMs = endMs;
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}
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summary(nowMs) {
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let missing = 0, run = 0, longest = 0;
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const start = (this.next + CAPACITY - this.count) % CAPACITY;
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for (let n = 0; n < this.count; n++) {
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if (this.history[(start + n) % CAPACITY]) run = 0;
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else { missing++; run++; longest = Math.max(longest, run); }
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}
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const age = this.lastEndMs !== null && Number.isFinite(nowMs) && nowMs >= this.lastEndMs
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? nowMs - this.lastEndMs : null;
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return {
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windowLimitMs: CAPACITY * this.windowMs,
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observedWindows: this.count,
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observedMs: this.count * this.windowMs,
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endMs: this.lastEndMs,
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observationAgeMs: age,
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coverageComplete: this.count === CAPACITY && age !== null && age <= 2 * this.windowMs,
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absentFraction: this.count ? missing / this.count : null,
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absenceMaxMs: this.count ? longest * this.windowMs : null,
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trailingAbsenceMs: this.count ? run * this.windowMs : null,
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interruptions: this.interruptions,
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};
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}
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}
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