Encode hidden data within NaN IEEE 754 floats
npm install nanbox
!Tests
!License
IEEE 754 encodes 32-bit floating points with 1 bit for the sign, 8 bits for the exponent, and 23 bits for the number part (mantissa). For the specific case of NaN (e.g. the result of dividing 0 by 0, or the square root of a negative number), the spec encodes this as 11111111 in the exponent. The sign and the mantissa can be anything, and the spec suggests this can be used for "diagnostic information". One/some of these bits is/are commonly used to indicate a quiet NaN (qNaN) which could be expected vs. a signaling NaN (sNaN) which could be unexpected and should trigger an halting exception. This behavior is however sometimes different on different hardware.
23 bits isn't much space, but conveniently the max size of a Unicode codepoint is 0x10FFFF, making it a 22-bit charset. When you encode your strings in UTF-32, you're only going to be using 22 of those bits, so masking the top portion with the NaN signature makes all of your characters NaNs.
``bash`
npm install --save nanbox
Use the named function toNaN to wrap your clandestine characters in NaNs, and then fromNaN to take them back out.
`javascript
import { fromNaN, toNaN } from 'nanbox'
const data = '酷'.codePointAt(0)
// => 0x9177
const boxed = toNaN(data)
// => NaN
const unboxed = fromNaN(boxed)
// => 0x9177
`
You could use this to encode your string as an array of NaNs. There's also the generic default function nanbox, which will detect which way you want to go.
`javascript
import nanbox from 'nanbox'
const str = '我的氣墊船裝滿了鰻魚'
const arr = str
.split('')
.map((c) => c.codePointAt(0))
.map(nanbox)
// => [ NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN ]
String.fromCodePoint(...arr.map(nanbox))
// => '我的氣墊船裝滿了鰻魚'
``
- Note: Usage does not entail useful.
- Note: Be careful storing or transporting, JSON has no standard way to represent NaN.
- Note: Sea Otters have evolved a pocket of loose skin under each forearm, which they use to store their favorite rock.
- https://twitter.com/im889/status/1256770029812514817
- https://anniecherkaev.com/the-secret-life-of-nan
- https://www.doc.ic.ac.uk/~eedwards/compsys/float/nan.html
- http://tom7.org/nand/
- https://stackoverflow.com/questions/27415935/does-unicode-have-a-defined-maximum-number-of-code-points