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Edit File: speedometer.js

'use strict';

/**
 * Calculate data maxRate
 * @param {Number} [samplesCount= 10]
 * @param {Number} [min= 1000]
 * @returns {Function}
 */
function speedometer(samplesCount, min) {
  samplesCount = samplesCount || 10;
  const bytes = new Array(samplesCount);
  const timestamps = new Array(samplesCount);
  let head = 0;
  let tail = 0;
  let firstSampleTS;

min = min !== undefined ? min : 1000;

return function push(chunkLength) {
    const now = Date.now();

const startedAt = timestamps[tail];

if (!firstSampleTS) {
      firstSampleTS = now;
    }

bytes[head] = chunkLength;
    timestamps[head] = now;

let i = tail;
    let bytesCount = 0;

while (i !== head) {
      bytesCount += bytes[i++];
      i = i % samplesCount;
    }

head = (head + 1) % samplesCount;

if (head === tail) {
      tail = (tail + 1) % samplesCount;
    }

if (now - firstSampleTS < min) {
      return;
    }

const passed = startedAt && now - startedAt;

return passed ? Math.round(bytesCount * 1000 / passed) : undefined;
  };
}

export default speedometer;

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