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Configuration error
; | |
var GetIntrinsic = require('get-intrinsic'); | |
var $pow = GetIntrinsic('%Math.pow%'); | |
module.exports = function bytesAsFloat64(rawBytes) { | |
// return new Float64Array(new Uint8Array(rawBytes).buffer)[0]; | |
/* | |
Let value be the byte elements of rawBytes concatenated and interpreted as a little-endian bit string encoding of an IEEE 754-2008 binary64 value. | |
If value is an IEEE 754-2008 binary64 NaN value, return the NaN Number value. | |
Return the Number value that corresponds to value. | |
*/ | |
var sign = rawBytes[7] & 0x80 ? -1 : 1; // first bit | |
var exponent = ((rawBytes[7] & 0x7F) << 4) // 7 bits from index 7 | |
| ((rawBytes[6] & 0xF0) >> 4); // 4 bits from index 6 | |
var mantissa = ((rawBytes[6] & 0x0F) * 0x1000000000000) // 4 bits from index 6 | |
+ (rawBytes[5] * 0x10000000000) // 8 bits from index 5 | |
+ (rawBytes[4] * 0x100000000) // 8 bits from index 4 | |
+ (rawBytes[3] * 0x1000000) // 8 bits from index 3 | |
+ (rawBytes[2] * 0x10000) // 8 bits from index 2 | |
+ (rawBytes[1] * 0x100) // 8 bits from index 1 | |
+ rawBytes[0]; // 8 bits from index 0 | |
if (exponent === 0 && mantissa === 0) { | |
return sign * 0; | |
} | |
if (exponent === 0x7FF && mantissa !== 0) { | |
return NaN; | |
} | |
if (exponent === 0x7FF && mantissa === 0) { | |
return sign * Infinity; | |
} | |
exponent -= 1023; // subtract the bias | |
// Handle subnormal numbers | |
if (exponent === -1023) { | |
return sign * mantissa * 5e-324; // $pow(2, -1022 - 52) | |
} | |
return sign * (1 + (mantissa / 0x10000000000000)) * $pow(2, exponent); | |
}; | |