mirror of
https://github.com/idanoo/GoScrobble.git
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34 lines
927 B
JavaScript
34 lines
927 B
JavaScript
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/* eslint no-bitwise: "off" */
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// Credit: https://github.com/paulmillr/es6-shim/
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"use strict";
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var pow = Math.pow;
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module.exports = function (bytes, ebits, fbits) {
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// Bytes to bits
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var bits = [], i, j, bit, str, bias, sign, e, fraction;
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for (i = bytes.length; i; i -= 1) {
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bit = bytes[i - 1];
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for (j = 8; j; j -= 1) {
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bits.push(bit % 2 ? 1 : 0);
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bit >>= 1;
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}
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}
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bits.reverse();
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str = bits.join("");
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// Unpack sign, exponent, fraction
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bias = (1 << (ebits - 1)) - 1;
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sign = parseInt(str.substring(0, 1), 2) ? -1 : 1;
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e = parseInt(str.substring(1, 1 + ebits), 2);
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fraction = parseInt(str.substring(1 + ebits), 2);
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// Produce number
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if (e === (1 << ebits) - 1) return fraction === 0 ? sign * Infinity : NaN;
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if (e > 0) return sign * pow(2, e - bias) * (1 + fraction / pow(2, fbits));
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if (fraction !== 0) return sign * pow(2, -(bias - 1)) * (fraction / pow(2, fbits));
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return sign < 0 ? -0 : 0;
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};
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