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");
|
}
|
