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function con(b) {
if ((b & 0xc0) === 0x80) {
return b & 0x3f;
} else {
throw new Error("invalid UTF-8 encoding");
}
}
function code(min, n) {
if (n < min || (0xd800 <= n && n < 0xe000) || n >= 0x10000) {
throw new Error("invalid UTF-8 encoding");
} else {
return n;
}
}
export function decode(bytes) {
return _decode(bytes)
.map(x => String.fromCharCode(x))
.join("");
}
function _decode(bytes) {
if (bytes.length === 0) {
return [];
}
/**
* 1 byte
*/
{
const [b1, ...bs] = bytes;
if (b1 < 0x80) {
return [code(0x0, b1), ..._decode(bs)];
}
if (b1 < 0xc0) {
throw new Error("invalid UTF-8 encoding");
}
}
/**
* 2 bytes
*/
{
const [b1, b2, ...bs] = bytes;
if (b1 < 0xe0) {
return [code(0x80, ((b1 & 0x1f) << 6) + con(b2)), ..._decode(bs)];
}
}
/**
* 3 bytes
*/
{
const [b1, b2, b3, ...bs] = bytes;
if (b1 < 0xf0) {
return [
code(0x800, ((b1 & 0x0f) << 12) + (con(b2) << 6) + con(b3)),
..._decode(bs)
];
}
}
/**
* 4 bytes
*/
{
const [b1, b2, b3, b4, ...bs] = bytes;
if (b1 < 0xf8) {
return [
code(
0x10000,
((((b1 & 0x07) << 18) + con(b2)) << 12) + (con(b3) << 6) + con(b4)
),
..._decode(bs)
];
}
}
throw new Error("invalid UTF-8 encoding");
}
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