45 lines
713 B
JavaScript
45 lines
713 B
JavaScript
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function con(n) {
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return 0x80 | (n & 0x3f);
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}
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export function encode(str) {
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const arr = str.split("").map(x => x.charCodeAt(0));
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return _encode(arr);
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}
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function _encode(arr) {
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if (arr.length === 0) {
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return [];
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}
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const [n, ...ns] = arr;
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if (n < 0) {
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throw new Error("utf8");
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}
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if (n < 0x80) {
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return [n, ..._encode(ns)];
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}
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if (n < 0x800) {
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return [0xc0 | (n >>> 6), con(n), ..._encode(ns)];
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}
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if (n < 0x10000) {
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return [0xe0 | (n >>> 12), con(n >>> 6), con(n), ..._encode(ns)];
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}
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if (n < 0x110000) {
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return [
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0xf0 | (n >>> 18),
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con(n >>> 12),
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con(n >>> 6),
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con(n),
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..._encode(ns)
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];
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}
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throw new Error("utf8");
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}
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