mirror of
https://github.com/fluencelabs/assemblyscript
synced 2025-04-25 15:12:12 +00:00
33 lines
980 B
JavaScript
33 lines
980 B
JavaScript
// set up decoding table
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var s64 = new Array(123);
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for (var i = 0; i < 64;) s64[i < 26 ? i + 65 : i < 52 ? i + 71 : i < 62 ? i - 4 : i - 59 | 43] = i++;
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module.exports = function(string) {
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// determine buffer length
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var length = string.length;
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if (length) {
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var n = 0, p = length;
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while (--p % 4 > 1 && string.charCodeAt(p) === 61) ++n;
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length = Math.ceil(length * 3) / 4 - n;
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}
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// decode to buffer
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var buffer = new Uint8Array(length);
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var j = 0, o = 0, t;
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for (var i = 0, k = string.length; i < k;) {
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var c = string.charCodeAt(i++);
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if (c === 61 && j > 1) break;
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if ((c = s64[c]) === undefined) throw Error();
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switch (j) {
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case 0: t = c; j = 1; break;
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case 1: buffer[o++] = t << 2 | (c & 48) >> 4; t = c; j = 2; break;
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case 2: buffer[o++] = (t & 15) << 4 | (c & 60) >> 2; t = c; j = 3; break;
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case 3: buffer[o++] = (t & 3) << 6 | c; j = 0; break;
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}
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}
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if (j === 1) throw Error();
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return buffer;
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};
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