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