decoder.js
2.15 KB
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"use strict";
Object.defineProperty(exports, "__esModule", {
value: true
});
exports.decode = decode;
function _toConsumableArray(arr) { if (Array.isArray(arr)) { for (var i = 0, arr2 = new Array(arr.length); i < arr.length; i++) { arr2[i] = arr[i]; } return arr2; } else { return Array.from(arr); } }
function _toArray(arr) { return Array.isArray(arr) ? arr : Array.from(arr); }
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;
}
}
function decode(bytes) {
return _decode(bytes).map(function (x) {
return String.fromCharCode(x);
}).join("");
}
function _decode(bytes) {
if (bytes.length === 0) {
return [];
}
/**
* 1 byte
*/
{
var _bytes = _toArray(bytes),
b1 = _bytes[0],
bs = _bytes.slice(1);
if (b1 < 0x80) {
return [code(0x0, b1)].concat(_toConsumableArray(_decode(bs)));
}
if (b1 < 0xc0) {
throw new Error("invalid UTF-8 encoding");
}
}
/**
* 2 bytes
*/
{
var _bytes2 = _toArray(bytes),
_b = _bytes2[0],
b2 = _bytes2[1],
_bs = _bytes2.slice(2);
if (_b < 0xe0) {
return [code(0x80, ((_b & 0x1f) << 6) + con(b2))].concat(_toConsumableArray(_decode(_bs)));
}
}
/**
* 3 bytes
*/
{
var _bytes3 = _toArray(bytes),
_b2 = _bytes3[0],
_b3 = _bytes3[1],
b3 = _bytes3[2],
_bs2 = _bytes3.slice(3);
if (_b2 < 0xf0) {
return [code(0x800, ((_b2 & 0x0f) << 12) + (con(_b3) << 6) + con(b3))].concat(_toConsumableArray(_decode(_bs2)));
}
}
/**
* 4 bytes
*/
{
var _bytes4 = _toArray(bytes),
_b4 = _bytes4[0],
_b5 = _bytes4[1],
_b6 = _bytes4[2],
b4 = _bytes4[3],
_bs3 = _bytes4.slice(4);
if (_b4 < 0xf8) {
return [code(0x10000, (((_b4 & 0x07) << 18) + con(_b5) << 12) + (con(_b6) << 6) + con(b4))].concat(_toConsumableArray(_decode(_bs3)));
}
}
throw new Error("invalid UTF-8 encoding");
}