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perf: trust Uint8Array.fromBase64 to check non-whitespace chars #47

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Merged
paulmillr merged 1 commit into from
Oct 13, 2025
+6 −2
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perf: trust Uint8Array.fromBase64 to check non-whitespace chars #47

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8 changes: 6 additions & 2 deletions index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -451,11 +451,15 @@ const hasBase64Builtin: boolean = /* @__PURE__ */ (() =>
typeof (Uint8Array as any).from([]).toBase64 === 'function' &&
typeof (Uint8Array as any).fromBase64 === 'function')();

// ASCII whitespace is U+0009 TAB, U+000A LF, U+000C FF, U+000D CR, or U+0020 SPACE
const ASCII_WHITESPACE = /[\t\n\f\r ]/

const decodeBase64Builtin = (s: string, isUrl: boolean) => {
astr('base64', s);
const re = isUrl ? /^[A-Za-z0-9=_-]+$/ : /^[A-Za-z0-9=+/]+$/;
const alphabet = isUrl ? 'base64url' : 'base64';
if (s.length > 0 && !re.test(s)) throw new Error('invalid base64');
// Per spec, .fromBase64 already throws on any other non-alphabet symbols except ASCII whitespace
// And checking just for whitspace makes decoding about 3x faster than a full range check
if (s.length > 0 && ASCII_WHITESPACE.test(s)) throw new Error('invalid base64');
return (Uint8Array as any).fromBase64(s, { alphabet, lastChunkHandling: 'strict' });
};

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