buffer-from 1.1.2: bufferFrom

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 pkg:npm/buffer-from@1.1.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/buffer-from@1.1.2
Demonstrate these symbols/APIs:
  - bufferFrom

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:b6013ceeb11829d4e3316de54d4782829f32fe434f115fb36b42507b597f7c0a","contract":["bufferFrom creates Buffer from string with default utf-8 encoding","bufferFrom creates Buffer from string with custom encoding like hex and base64","bufferFrom creates Buffer from array of byte values","bufferFrom creates Buffer from existing Buffer making a copy","bufferFrom creates Buffer from ArrayBuffer with offset and length slicing","bufferFrom throws TypeError when value is a number","bufferFrom throws TypeError when encoding is invalid","bufferFrom throws RangeError when ArrayBuffer offset or length is out of bounds"],"goal":"verify pkg:npm/buffer-from@1.1.2","kind":"HOW","packages":["pkg:npm/buffer-from@1.1.2"],"schemaVersion":1,"symbols":["bufferFrom"]},"contractCommand":["node","test/contract.mjs"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"npm","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"npm","schemaVersion":1},"license":"MIT-0","packages":["pkg:npm/buffer-from@1.1.2"],"schemaVersion":1,"subject":"pkg:npm/buffer-from@1.1.2","symbols":["bufferFrom"],"verifierAdapter":"node-typescript@1"}

{
  "name": "buffer-from-verification",
  "version": "1.0.0",
  "lockfileVersion": 3,
  "requires": true,
  "packages": {
    "": {
      "name": "buffer-from-verification",
      "version": "1.0.0",
      "dependencies": {
        "buffer-from": "1.1.2"
      }
    },
    "node_modules/buffer-from": {
      "version": "1.1.2",
      "resolved": "https://registry.npmjs.org/buffer-from/-/buffer-from-1.1.2.tgz",
      "integrity": "sha512-E+XQCRwSbaaiChtv6k6Dwgc+bx+Bs6vuKJHHl5kox/BaKbhiXzqQOwK4cO22yElGp2OCmjwVhT3HmxgyPGnJfQ==",
      "license": "MIT"
    }
  }
}

{
  "name": "buffer-from-verification",
  "version": "1.0.0",
  "private": true,
  "description": "Clean-room verification for buffer-from",
  "dependencies": {
    "buffer-from": "1.1.2"
  }
}

{
  "schemaVersion": 1,
  "goal": "verify pkg:npm/buffer-from@1.1.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/buffer-from@1.1.2"
  ],
  "symbols": [
    "bufferFrom"
  ]
}

import assert from 'node:assert';
import bufferFrom from 'buffer-from';

// 1. bufferFrom creates Buffer from string with default utf-8 encoding
const strBuf = bufferFrom('hello world');
assert.ok(Buffer.isBuffer(strBuf));
assert.strictEqual(strBuf.toString('utf8'), 'hello world');
assert.strictEqual(strBuf.length, 11);

// 2. bufferFrom creates Buffer from string with custom encoding like hex and base64
const hexBuf = bufferFrom('68656c6c6f', 'hex');
assert.strictEqual(hexBuf.toString('utf8'), 'hello');
const b64Buf = bufferFrom('aGVsbG8=', 'base64');
assert.strictEqual(b64Buf.toString('utf8'), 'hello');

// 3. bufferFrom creates Buffer from array of byte values
const arrBuf = bufferFrom([104, 101, 108, 108, 111]);
assert.ok(Buffer.isBuffer(arrBuf));
assert.strictEqual(arrBuf.toString('utf8'), 'hello');
assert.strictEqual(arrBuf.length, 5);

// 4. bufferFrom creates Buffer from existing Buffer making a copy
const original = Buffer.from('copy-test');
const copied = bufferFrom(original);
assert.ok(Buffer.isBuffer(copied));
assert.strictEqual(copied.toString('utf8'), 'copy-test');
original[0] = 0x78; // mutate original to ensure independent copy
assert.strictEqual(copied.toString('utf8'), 'copy-test');

// 5. bufferFrom creates Buffer from ArrayBuffer with offset and length slicing
const ab = new Uint8Array([1, 2, 3, 4, 5, 6]).buffer;
const abBuf = bufferFrom(ab, 2, 3);
assert.ok(Buffer.isBuffer(abBuf));
assert.strictEqual(abBuf.length, 3);
assert.deepStrictEqual(Array.from(abBuf), [3, 4, 5]);

// 6. bufferFrom throws TypeError when value is a number
assert.throws(
  () => bufferFrom(123),
  {
    name: 'TypeError',
    message: '"value" argument must not be a number'
  }
);

// 7. bufferFrom throws TypeError when encoding is invalid
assert.throws(
  () => bufferFrom('test', 'invalid-encoding-xyz'),
  {
    name: 'TypeError',
    message: '"encoding" must be a valid string encoding'
  }
);

// 8. bufferFrom throws RangeError when ArrayBuffer offset or length is out of bounds
assert.throws(
  () => bufferFrom(new ArrayBuffer(8), 10),
  {
    name: 'RangeError',
    message: "'offset' is out of bounds"
  }
);
assert.throws(
  () => bufferFrom(new ArrayBuffer(8), 2, 10),
  {
    name: 'RangeError',
    message: "'length' is out of bounds"
  }
);

console.log('Contract passed');