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buffer: fix single-character string filling · nodejs/node@9eaa721 · GitHub

/ node Public

Commit 9eaa721

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addaleax
authored and
MylesBorins
committed
buffer: fix single-character string filling
Fix the fast path for `buffer.fill()` with a single-character string. The fast path only works for strings that are equivalent to a single-byte buffer, but that condition was not checked properly for the `utf8` or `utf16le` encodings and is always true for the `latin1` encoding. This change fixes these problems. Fixes: #9836 PR-URL: #9837 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl> Reviewed-By: Trevor Norris <trev.norris@gmail.com>
1 parent 60d5f6b commit 9eaa721

2 files changed

Lines changed: 42 additions & 12 deletions

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‎lib/buffer.js‎

Lines changed: 15 additions & 11 deletions
Original file line numberDiff line numberDiff line change
@@ -664,23 +664,27 @@ Buffer.prototype.fill = function fill(val, start, end, encoding) {
664664
encoding = end;
665665
end = this.length;
666666
}
667-
if (val.length === 1) {
668-
var code = val.charCodeAt(0);
669-
if (code < 256)
670-
val = code;
671-
}
672-
if (val.length === 0) {
673-
// Previously, if val === '', the Buffer would not fill,
674-
// which is rather surprising.
675-
val = 0;
676-
}
667+
677668
if (encoding !== undefined && typeof encoding !== 'string') {
678669
throw new TypeError('encoding must be a string');
679670
}
680-
if (typeof encoding === 'string' && !Buffer.isEncoding(encoding)) {
671+
var normalizedEncoding = internalUtil.normalizeEncoding(encoding);
672+
if (normalizedEncoding === undefined) {
681673
throw new TypeError('Unknown encoding: ' + encoding);
682674
}
683675

676+
if (val.length === 0) {
677+
// Previously, if val === '', the Buffer would not fill,
678+
// which is rather surprising.
679+
val = 0;
680+
} else if (val.length === 1) {
681+
var code = val.charCodeAt(0);
682+
if ((normalizedEncoding === 'utf8' && code < 128) ||
683+
normalizedEncoding === 'latin1') {
684+
// Fast path: If `val` fits into a single byte, use that numeric value.
685+
val = code;
686+
}
687+
}
684688
} else if (typeof val === 'number') {
685689
val = val & 255;
686690
}

‎test/parallel/test-buffer-fill.js‎

Lines changed: 27 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -395,11 +395,37 @@ assert.throws(() => {
395395
buf.fill('');
396396
}, /^RangeError: out of range index$/);
397397

398-
399398
assert.deepStrictEqual(
400399
Buffer.allocUnsafeSlow(16).fill('ab', 'utf16le'),
401400
Buffer.from('61006200610062006100620061006200', 'hex'));
402401

403402
assert.deepStrictEqual(
404403
Buffer.allocUnsafeSlow(15).fill('ab', 'utf16le'),
405404
Buffer.from('610062006100620061006200610062', 'hex'));
405+
406+
assert.deepStrictEqual(
407+
Buffer.allocUnsafeSlow(16).fill('ab', 'utf16le'),
408+
Buffer.from('61006200610062006100620061006200', 'hex'));
409+
assert.deepStrictEqual(
410+
Buffer.allocUnsafeSlow(16).fill('a', 'utf16le'),
411+
Buffer.from('61006100610061006100610061006100', 'hex'));
412+
413+
assert.strictEqual(
414+
Buffer.allocUnsafeSlow(16).fill('a', 'utf16le').toString('utf16le'),
415+
'a'.repeat(8));
416+
assert.strictEqual(
417+
Buffer.allocUnsafeSlow(16).fill('a', 'latin1').toString('latin1'),
418+
'a'.repeat(16));
419+
assert.strictEqual(
420+
Buffer.allocUnsafeSlow(16).fill('a', 'utf8').toString('utf8'),
421+
'a'.repeat(16));
422+
423+
assert.strictEqual(
424+
Buffer.allocUnsafeSlow(16).fill('Љ', 'utf16le').toString('utf16le'),
425+
'Љ'.repeat(8));
426+
assert.strictEqual(
427+
Buffer.allocUnsafeSlow(16).fill('Љ', 'latin1').toString('latin1'),
428+
'\t'.repeat(16));
429+
assert.strictEqual(
430+
Buffer.allocUnsafeSlow(16).fill('Љ', 'utf8').toString('utf8'),
431+
'Љ'.repeat(8));

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