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47 lines
1.2 KiB
47 lines
1.2 KiB
'use strict'; |
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var $pow = require('math-intrinsics/pow'); |
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module.exports = function bytesAsFloat32(rawBytes) { |
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// return new $Float16Array(new $Uint8Array(rawBytes).buffer)[0]; |
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/* |
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Let value be the byte elements of rawBytes concatenated and interpreted as a little-endian bit string encoding of an IEEE 754-2019 binary16 value. |
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If value is a NaN, return NaN. |
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Return the Number value that corresponds to value. |
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*/ |
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var bits = (rawBytes[1] << 8) | rawBytes[0]; |
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// extract sign, exponent, mantissa |
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var sign = bits & 0x8000 ? -1 : 1; |
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var exponent = (bits & 0x7C00) >> 10; |
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var mantissa = bits & 0x03FF; |
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// zero (±0) |
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if (exponent === 0 && mantissa === 0) { |
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return sign === 1 ? 0 : -0; |
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} |
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// infinities |
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if (exponent === 0x1F && mantissa === 0) { |
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return sign === 1 ? Infinity : -Infinity; |
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} |
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// NaN |
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if (exponent === 0x1F && mantissa !== 0) { |
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return NaN; |
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} |
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// remove bias (15) |
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exponent -= 15; |
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// subnormals |
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if (exponent === -15) { |
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// value = sign * (mantissa) * 2^(1-bias-10) = mantissa * 2^(-14-10) |
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return sign * mantissa * $pow(2, -24); |
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} |
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// normals |
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// value = sign * (1 + mantissa/2^10) * 2^exponent |
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return sign * (1 + (mantissa * $pow(2, -10))) * $pow(2, exponent); |
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};
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