benchmark.js

const { performance } = require("perf_hooks");

const minus = "-".charCodeAt(0);
const plus = "+".charCodeAt(0);
const dot = ".".charCodeAt(0);
const exponent = "e".charCodeAt(0);
const exponentCapital = "E".charCodeAt(0);

function bufToFloat(buf, start, len) {
  let offset = start;
  let result = 0;
  const end = offset + len;
  let factor = 1;
  let pastDot = false;
  let charCode = 0;
  if (buf[offset] === minus) {
    offset++;
    factor = -1;
  }
  if (buf[offset] === plus) {
    offset++; // just ignore
  }
  while (offset < end) {
    charCode = buf[offset];
    if (charCode === dot) {
      pastDot = true;
      offset++;
    } else if (charCode === exponent || charCode === exponentCapital) {
      offset++;
      const exponentValue = this.parseInt(end - this.offset);
      return (result / factor) * Math.pow(10, exponentValue);
    } else {
      result *= 10;
      result += buf[offset] - 48;
      offset++;
      if (pastDot) {
        factor = factor * 10;
      }
    }
  }
  return result / factor;
}

function pad(str) {
  if (str.length > 10) {
    return str.slice(0, 10);
  }
  const zeroes = "0000000000";
  return str + zeroes.slice(0, 10 - str.length);
}

const buf = Buffer.alloc(10000000 * 10);
for (let offset = 0; offset < buf.length; offset += 10) {
  const str = pad(Math.random().toString(10));
  buf.write(str, offset);
}

function benchmark() {
  let acc = 0;
  const start = performance.now();
  for (let offset = 0; offset < buf.length; offset += 10) {
    const str = buf.toString("ascii", offset, offset + 10);
    const number = parseFloat(str, 10);
    acc += number;
  }
  const duration = performance.now() - start;
  console.log(`parsing done (global.parseFloat), resul: ${acc} in ${duration} ms`);
}

function benchmark2() {
    let acc = 0;
    const start = performance.now();
    for (let offset = 0; offset < buf.length; offset += 10) {
      const number = bufToFloat(buf, offset, 10);
      acc += number;
    }
    const duration = performance.now() - start;
    console.log(`parsing done, resul: ${acc} in ${duration} ms`);
}
  

for (let i=0; i < 10; ++i) {
  benchmark();
}

for (let i=0; i < 10; ++i) {
  benchmark2();
}