bytesAsFloat32.js 1.2 KB

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  1. 'use strict';
  2. var GetIntrinsic = require('get-intrinsic');
  3. var $pow = GetIntrinsic('%Math.pow%');
  4. module.exports = function bytesAsFloat32(rawBytes) {
  5. // return new $Float32Array(new $Uint8Array(rawBytes).buffer)[0];
  6. /*
  7. 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.
  8. If value is an IEEE 754-2008 binary32 NaN value, return the NaN Number value.
  9. Return the Number value that corresponds to value.
  10. */
  11. var sign = rawBytes[3] & 0x80 ? -1 : 1; // Check the sign bit
  12. var exponent = ((rawBytes[3] & 0x7F) << 1)
  13. | (rawBytes[2] >> 7); // Combine bits for exponent
  14. var mantissa = ((rawBytes[2] & 0x7F) << 16)
  15. | (rawBytes[1] << 8)
  16. | rawBytes[0]; // Combine bits for mantissa
  17. if (exponent === 0 && mantissa === 0) {
  18. return sign === 1 ? 0 : -0;
  19. }
  20. if (exponent === 0xFF && mantissa === 0) {
  21. return sign === 1 ? Infinity : -Infinity;
  22. }
  23. if (exponent === 0xFF && mantissa !== 0) {
  24. return NaN;
  25. }
  26. exponent -= 127; // subtract the bias
  27. if (exponent === -127) {
  28. return sign * mantissa * $pow(2, -126 - 23);
  29. }
  30. return sign * (1 + (mantissa * $pow(2, -23))) * $pow(2, exponent);
  31. };