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36 lines
1.1 KiB
36 lines
1.1 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 $Float32Array(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 754-2008 binary32 value. |
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If value is an IEEE 754-2008 binary32 NaN value, return the NaN Number value. |
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Return the Number value that corresponds to value. |
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*/ |
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var sign = rawBytes[3] & 0x80 ? -1 : 1; // Check the sign bit |
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var exponent = ((rawBytes[3] & 0x7F) << 1) |
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| (rawBytes[2] >> 7); // Combine bits for exponent |
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var mantissa = ((rawBytes[2] & 0x7F) << 16) |
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| (rawBytes[1] << 8) |
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| rawBytes[0]; // Combine bits for mantissa |
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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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if (exponent === 0xFF && mantissa === 0) { |
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return sign === 1 ? Infinity : -Infinity; |
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} |
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if (exponent === 0xFF && mantissa !== 0) { |
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return NaN; |
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} |
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exponent -= 127; // subtract the bias |
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if (exponent === -127) { |
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return sign * mantissa * $pow(2, -126 - 23); |
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} |
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return sign * (1 + (mantissa * $pow(2, -23))) * $pow(2, exponent); |
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};
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