bytesAsFloat32.js 1.1 KB

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