node/test/parallel/test-string-decoder.js

'use strict';
require('../common');
const assert = require('assert');
const inspect = require('util').inspect;
const StringDecoder = require('string_decoder').StringDecoder;

// Test default encoding
let decoder = new StringDecoder();
assert.strictEqual(decoder.encoding, 'utf8');

// UTF-8
test('utf-8', Buffer.from('$', 'utf-8'), '$');
test('utf-8', Buffer.from('¢', 'utf-8'), '¢');
test('utf-8', Buffer.from('€', 'utf-8'), '€');
test('utf-8', Buffer.from('𤭢', 'utf-8'), '𤭢');
// A mixed ascii and non-ascii string
// Test stolen from deps/v8/test/cctest/test-strings.cc
// U+02E4 -> CB A4
// U+0064 -> 64
// U+12E4 -> E1 8B A4
// U+0030 -> 30
// U+3045 -> E3 81 85
test(
  'utf-8',
  Buffer.from([0xCB, 0xA4, 0x64, 0xE1, 0x8B, 0xA4, 0x30, 0xE3, 0x81, 0x85]),
  '\u02e4\u0064\u12e4\u0030\u3045'
);

// Some invalid input, known to have caused trouble with chunking
// in https://github.com/nodejs/node/pull/7310#issuecomment-226445923
// 00: |00000000 ASCII
// 41: |01000001 ASCII
// B8: 10|111000 continuation
// CC: 110|01100 two-byte head
// E2: 1110|0010 three-byte head
// F0: 11110|000 four-byte head
// F1: 11110|001'another four-byte head
// FB: 111110|11 "five-byte head", not UTF-8
test('utf-8', Buffer.from('C9B5A941', 'hex'), '\u0275\ufffdA');
test('utf-8', Buffer.from('E2', 'hex'), '\ufffd');
test('utf-8', Buffer.from('E241', 'hex'), '\ufffdA');
test('utf-8', Buffer.from('CCCCB8', 'hex'), '\ufffd\u0338');
test('utf-8', Buffer.from('F0B841', 'hex'), '\ufffdA');
test('utf-8', Buffer.from('F1CCB8', 'hex'), '\ufffd\u0338');
test('utf-8', Buffer.from('F0FB00', 'hex'), '\ufffd\ufffd\0');
test('utf-8', Buffer.from('CCE2B8B8', 'hex'), '\ufffd\u2e38');
test('utf-8', Buffer.from('E2B8CCB8', 'hex'), '\ufffd\u0338');
test('utf-8', Buffer.from('E2FBCC01', 'hex'), '\ufffd\ufffd\ufffd\u0001');
test('utf-8', Buffer.from('CCB8CDB9', 'hex'), '\u0338\u0379');
// CESU-8 of U+1D40D
test('utf-8', Buffer.from('EDA0B5EDB08D', 'hex'), '\ufffd\ufffd');

// UCS-2
test('ucs2', Buffer.from('ababc', 'ucs2'), 'ababc');

// UTF-16LE
test('utf16le', Buffer.from('3DD84DDC', 'hex'), '\ud83d\udc4d'); // thumbs up

// Additional UTF-8 tests
decoder = new StringDecoder('utf8');
assert.strictEqual(decoder.write(Buffer.from('E1', 'hex')), '');
assert.strictEqual(decoder.end(), '\ufffd');

decoder = new StringDecoder('utf8');
assert.strictEqual(decoder.write(Buffer.from('E18B', 'hex')), '');
assert.strictEqual(decoder.end(), '\ufffd');

decoder = new StringDecoder('utf8');
assert.strictEqual(decoder.write(Buffer.from('\ufffd')), '\ufffd');
assert.strictEqual(decoder.end(), '');

decoder = new StringDecoder('utf8');
assert.strictEqual(decoder.write(Buffer.from('\ufffd\ufffd\ufffd')),
                   '\ufffd\ufffd\ufffd');
assert.strictEqual(decoder.end(), '');

decoder = new StringDecoder('utf8');
assert.strictEqual(decoder.write(Buffer.from('EFBFBDE2', 'hex')), '\ufffd');
assert.strictEqual(decoder.end(), '\ufffd');

decoder = new StringDecoder('utf8');
assert.strictEqual(decoder.write(Buffer.from('F1', 'hex')), '');
assert.strictEqual(decoder.write(Buffer.from('41F2', 'hex')), '\ufffdA');
assert.strictEqual(decoder.end(), '\ufffd');


// Additional UTF-16LE surrogate pair tests
decoder = new StringDecoder('utf16le');
assert.strictEqual(decoder.write(Buffer.from('3DD8', 'hex')), '');
assert.strictEqual(decoder.write(Buffer.from('4D', 'hex')), '');
assert.strictEqual(decoder.write(Buffer.from('DC', 'hex')), '\ud83d\udc4d');
assert.strictEqual(decoder.end(), '');

decoder = new StringDecoder('utf16le');
assert.strictEqual(decoder.write(Buffer.from('3DD8', 'hex')), '');
assert.strictEqual(decoder.end(), '\ud83d');

decoder = new StringDecoder('utf16le');
assert.strictEqual(decoder.write(Buffer.from('3DD8', 'hex')), '');
assert.strictEqual(decoder.write(Buffer.from('4D', 'hex')), '');
assert.strictEqual(decoder.end(), '\ud83d');

assert.throws(() => {
  new StringDecoder(1);
}, /^Error: Unknown encoding: 1$/);

assert.throws(() => {
  new StringDecoder('test');
}, /^Error: Unknown encoding: test$/);

// test verifies that StringDecoder will correctly decode the given input
// buffer with the given encoding to the expected output. It will attempt all
// possible ways to write() the input buffer, see writeSequences(). The
// singleSequence allows for easy debugging of a specific sequence which is
// useful in case of test failures.
function test(encoding, input, expected, singleSequence) {
  let sequences;
  if (!singleSequence) {
    sequences = writeSequences(input.length);
  } else {
    sequences = [singleSequence];
  }
  sequences.forEach((sequence) => {
    const decoder = new StringDecoder(encoding);
    let output = '';
    sequence.forEach((write) => {
      output += decoder.write(input.slice(write[0], write[1]));
    });
    output += decoder.end();
    if (output !== expected) {
      const message =
        'Expected "' + unicodeEscape(expected) + '", ' +
        'but got "' + unicodeEscape(output) + '"\n' +
        'input: ' + input.toString('hex').match(/.{2}/g) + '\n' +
        'Write sequence: ' + JSON.stringify(sequence) + '\n' +
        'Full Decoder State: ' + inspect(decoder);
      assert.fail(output, expected, message);
    }
  });
}

// unicodeEscape prints the str contents as unicode escape codes.
function unicodeEscape(str) {
  let r = '';
  for (let i = 0; i < str.length; i++) {
    r += '\\u' + str.charCodeAt(i).toString(16);
  }
  return r;
}

// writeSequences returns an array of arrays that describes all possible ways a
// buffer of the given length could be split up and passed to sequential write
// calls.
//
// e.G. writeSequences(3) will return: [
//   [ [ 0, 3 ] ],
//   [ [ 0, 2 ], [ 2, 3 ] ],
//   [ [ 0, 1 ], [ 1, 3 ] ],
//   [ [ 0, 1 ], [ 1, 2 ], [ 2, 3 ] ]
// ]
function writeSequences(length, start, sequence) {
  if (start === undefined) {
    start = 0;
    sequence = [];
  } else if (start === length) {
    return [sequence];
  }
  let sequences = [];
  for (let end = length; end > start; end--) {
    const subSequence = sequence.concat([[start, end]]);
    const subSequences = writeSequences(length, end, subSequence, sequences);
    sequences = sequences.concat(subSequences);
  }
  return sequences;
}