pvutils 1.2.0: nearestPowerOf2

audit=false

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pvutils.nearestPowerOf2 in pkg:npm/pvutils@1.2.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/pvutils@1.2.0
Demonstrate these symbols/APIs:
  - pvutils.nearestPowerOf2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:20c0ac336922b0f2f9d03ce829497c13a9ed03bb1200e3b1ef9205a480d1703f","contract":["nearestPowerOf2 returns 0 for an input length of 1","nearestPowerOf2 returns exact power-of-2 exponents for inputs that are exact powers of 2","nearestPowerOf2 rounds to the nearest integer exponent for input lengths between powers of 2","nearestPowerOf2 returns the base-2 exponent rather than the evaluated power-of-2 value itself","nearestPowerOf2 computes buffer allocation exponents to size power-of-2 buffers"],"goal":"verify pvutils.nearestPowerOf2 in pkg:npm/pvutils@1.2.0","kind":"HOW","packages":["pkg:npm/pvutils@1.2.0"],"schemaVersion":1,"symbols":["pvutils.nearestPowerOf2"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","language":"javascript","libc":"glibc","libcVersion":"2.39","moduleSystem":"esm","os":"linux","osVersionBucket":"24","packageManager":"npm","packageManagerVersion":"10.9.8","runtime":"node","runtimeVersion":"22.23.2","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/pvutils@1.2.0"],"schemaVersion":1,"subject":"pkg:npm/pvutils@1.2.0","symbols":["pvutils.nearestPowerOf2"],"verifierAdapter":"node-typescript@1"}

{
  "name": "sample-pvutils-nearestpowerof2",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "sample-pvutils-nearestpowerof2",
      "version": "1.0.0",
      "license": "MIT-0",
      "dependencies": {
        "pvutils": "1.2.0"
      }
    },
    "node_modules/pvutils": {
      "version": "1.2.0",
      "resolved": "https://registry.npmjs.org/pvutils/-/pvutils-1.2.0.tgz",
      "integrity": "sha512-BbubeCEyTuQjVMakvJQ/Sxbc93F2pwmbsxONT/ZRrwU7Ua38d8unYTwXpTVLAKJ4BDuH9IGztCjQcd/N/39Dvg==",
      "license": "MIT",
      "engines": {
        "node": ">=16.0.0"
      }
    }
  }
}

{
  "name": "sample-pvutils-nearestpowerof2",
  "version": "1.0.0",
  "type": "module",
  "private": true,
  "license": "MIT-0",
  "scripts": {
    "test": "node test/contract.mjs"
  },
  "dependencies": {
    "pvutils": "1.2.0"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pvutils.nearestPowerOf2 in pkg:npm/pvutils@1.2.0",
  "kind": "HOW",
  "packages": [
    "pkg:npm/pvutils@1.2.0"
  ],
  "symbols": [
    "pvutils.nearestPowerOf2"
  ]
}

import { nearestPowerOf2 } from 'pvutils';

/**
 * Returns the base-2 power (exponent) nearest to the input length.
 *
 * Note: The return value is the integer exponent k (where 2^k ~ length),
 * not the evaluated value 2^k itself.
 *
 * @param {number} length - Current length of existing array or target size.
 * @returns {number} The integer exponent of the nearest power of 2.
 */
export function getNearestPowerOf2(length) {
  return nearestPowerOf2(length);
}

/**
 * Calculates the buffer size corresponding to the nearest power of 2.
 *
 * @param {number} length - Current length or requested capacity.
 * @returns {number} The evaluated power of 2 (i.e. 2 ** exponent).
 */
export function calculatePowerOf2BufferSize(length) {
  const exponent = nearestPowerOf2(length);
  return 2 ** exponent;
}

export { nearestPowerOf2 };
export default nearestPowerOf2;

import assert from 'node:assert/strict';
import { nearestPowerOf2 } from 'pvutils';
import { getNearestPowerOf2, calculatePowerOf2BufferSize } from '../src/index.mjs';

// 1. nearestPowerOf2 returns 0 for an input length of 1
{
  const result = nearestPowerOf2(1);
  assert.equal(typeof result, 'number');
  assert.equal(result, 0);

  const helperResult = getNearestPowerOf2(1);
  assert.equal(helperResult, 0);
}

// 2. nearestPowerOf2 returns exact power-of-2 exponents for inputs that are exact powers of 2
{
  const powers = [
    { input: 2, expected: 1 },
    { input: 4, expected: 2 },
    { input: 8, expected: 3 },
    { input: 16, expected: 4 },
    { input: 32, expected: 5 },
    { input: 64, expected: 6 },
    { input: 128, expected: 7 },
    { input: 256, expected: 8 },
    { input: 512, expected: 9 },
    { input: 1024, expected: 10 },
    { input: 65536, expected: 16 }
  ];

  for (const { input, expected } of powers) {
    assert.equal(
      nearestPowerOf2(input),
      expected,
      `nearestPowerOf2(${input}) must return exponent ${expected}`
    );
    assert.equal(
      getNearestPowerOf2(input),
      expected,
      `getNearestPowerOf2(${input}) must return exponent ${expected}`
    );
  }
}

// 3. nearestPowerOf2 rounds to the nearest integer exponent for input lengths between powers of 2
{
  assert.equal(nearestPowerOf2(3), 2);
  assert.equal(nearestPowerOf2(5), 2);
  assert.equal(nearestPowerOf2(6), 3);
  assert.equal(nearestPowerOf2(7), 3);
  assert.equal(nearestPowerOf2(10), 3);
  assert.equal(nearestPowerOf2(12), 4);
}

// 4. nearestPowerOf2 returns the base-2 exponent rather than the evaluated power-of-2 value itself
{
  const input = 8;
  const exponent = nearestPowerOf2(input);

  assert.notEqual(exponent, input);
  assert.equal(exponent, 3);
  assert.equal(2 ** exponent, input);

  const input16 = 16;
  const exponent16 = nearestPowerOf2(input16);
  assert.notEqual(exponent16, input16);
  assert.equal(exponent16, 4);
  assert.equal(2 ** exponent16, input16);
}

// 5. nearestPowerOf2 computes buffer allocation exponents to size power-of-2 buffers
{
  assert.equal(calculatePowerOf2BufferSize(1), 1);
  assert.equal(calculatePowerOf2BufferSize(2), 2);
  assert.equal(calculatePowerOf2BufferSize(3), 4);
  assert.equal(calculatePowerOf2BufferSize(4), 4);
  assert.equal(calculatePowerOf2BufferSize(5), 4);
  assert.equal(calculatePowerOf2BufferSize(6), 8);
  assert.equal(calculatePowerOf2BufferSize(8), 8);
  assert.equal(calculatePowerOf2BufferSize(12), 16);
}

console.log('Contract tests passed successfully.');