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Use TextEncoder/TextDecoder for UTF-8 #55

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Merged
matmen merged 1 commit into from
Oct 15, 2026
Merged

Use TextEncoder/TextDecoder for UTF-8 #55

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59 changes: 8 additions & 51 deletions src/util/utf8.ts
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Original file line number Diff line number Diff line change
@@ -1,60 +1,17 @@
// UTF-8 helpers, so the library doesn't depend on TextEncoder/TextDecoder being available
// TextEncoder and TextDecoder are web APIs, not part of the es2022 lib: declare the parts used here
declare const TextEncoder: { new(): { encode(text: string): Uint8Array } };
declare const TextDecoder: { new(): { decode(bytes: Uint8Array): string } };

export function encode(text: string): Uint8Array {
const out: number[] = [];

for (const char of text) {
const c = char.codePointAt(0) as number;
if (c < 0x80) out.push(c);
else if (c < 0x800) out.push(0xc0 | c >> 6, 0x80 | c & 63);
else if (c < 0x10000) out.push(0xe0 | c >> 12, 0x80 | c >> 6 & 63, 0x80 | c & 63);
else out.push(0xf0 | c >> 18, 0x80 | c >> 12 & 63, 0x80 | c >> 6 & 63, 0x80 | c & 63);
}
const encoder = new TextEncoder();
const decoder = new TextDecoder();

return Uint8Array.from(out);
export function encode(text: string): Uint8Array {
return encoder.encode(text);
}

/**
* Decodes UTF-8, replacing invalid sequences with U+FFFD and skipping a leading byte order mark
*/
export function decode(bytes: Uint8Array): string {
let out = '';
let i = bytes[0] === 0xef && bytes[1] === 0xbb && bytes[2] === 0xbf ? 3 : 0;

while (i < bytes.length) {
const b = bytes[i++];
let c: number, extra: number;

if (b < 0x80) {
c = b;
extra = 0;
} else if (b >= 0xc2 && b < 0xe0) {
c = b & 31;
extra = 1;
} else if (b >= 0xe0 && b < 0xf0) {
c = b & 15;
extra = 2;
} else if (b >= 0xf0 && b < 0xf5) {
c = b & 7;
extra = 3;
} else {
out += '�';
continue;
}

let valid = true;
for (let k = 0; k < extra; k++) {
const next = bytes[i];
if (next === undefined || (next & 0xc0) !== 0x80) {
valid = false;
break;
}
c = c << 6 | next & 63;
i++;
}

out += valid && c <= 0x10ffff ? String.fromCodePoint(c) : '�';
}

return out;
return decoder.decode(bytes);
}
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