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  1. # Parser function for floating point hexadecimals
  2. [![license](https://img.shields.io/github/license/maurobringolf/@webassemblyjs/floating-point-hex-parser.svg)]()
  3. [![GitHub last commit](https://img.shields.io/github/last-commit/maurobringolf/@webassemblyjs/floating-point-hex-parser.svg)]()
  4. [![npm](https://img.shields.io/npm/v/@webassemblyjs/floating-point-hex-parser.svg)]()
  5. > A JavaScript function to parse floating point hexadecimals as defined by the [WebAssembly specification](https://webassembly.github.io/spec/core/text/values.html#text-hexfloat).
  6. ## Usage
  7. ```javascript
  8. import parseHexFloat from '@webassemblyjs/floating-point-hex-parser'
  9. parseHexFloat('0x1p-1') // 0.5
  10. parseHexFloat('0x1.921fb54442d18p+2') // 6.283185307179586
  11. ```
  12. ## Tests
  13. This module is tested in two ways. The first one is through a small set of test cases that can be found in [test/regular.test.js](https://github.com/maurobringolf/@webassemblyjs/floating-point-hex-parser/blob/master/test/regular.test.js). The second one is non-deterministic (sometimes called *fuzzing*):
  14. 1. Generate a random IEEE754 double precision value `x`.
  15. 1. Compute its representation `y` in floating point hexadecimal format using the C standard library function `printf` since C supports this format.
  16. 1. Give both values to JS testcase and see if `parseHexFloat(y) === x`.
  17. By default one `npm test` run tests 100 random samples. If you want to do more, you can set the environment variable `FUZZ_AMOUNT` to whatever number of runs you'd like. Because it uses one child process for each sample, it is really slow though. For more details about the randomized tests see [the source](https://github.com/maurobringolf/@webassemblyjs/floating-point-hex-parser/tree/master/test/fuzzing).
  18. ## Links
  19. * [maurobringolf.ch/2017/12/hexadecimal-floating-point-notation/](https://maurobringolf.ch/2017/12/hexadecimal-floating-point-notation/)
  20. * [github.com/xtuc/js-webassembly-interpreter/issues/32](https://github.com/xtuc/js-webassembly-interpreter/issues/32)
  21. * [github.com/WebAssembly/design/issues/292](https://github.com/WebAssembly/design/issues/292)