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33 lines
832 B
33 lines
832 B
// 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, b, str,
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bias, s, e, f;
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for (i = bytes.length; i; i -= 1) {
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b = bytes[i - 1];
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for (j = 8; j; j -= 1) {
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bits.push(b % 2 ? 1 : 0);
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b = b >> 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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s = parseInt(str.substring(0, 1), 2) ? -1 : 1;
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e = parseInt(str.substring(1, 1 + ebits), 2);
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f = parseInt(str.substring(1 + ebits), 2);
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// Produce number
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if (e === (1 << ebits) - 1) return f !== 0 ? NaN : s * Infinity;
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if (e > 0) return s * pow(2, e - bias) * (1 + f / pow(2, fbits));
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if (f !== 0) return s * pow(2, -(bias - 1)) * (f / pow(2, fbits));
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return s < 0 ? -0 : 0;
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};
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