Telememer: a JS library to encode/decode information to/from Casio module 2747/5574 Telememo 30 format

telememer.js

// Telememer: a JS library to encode/decode information to/from Casio module 2747/5574 Telememo 30 format
// Supports up to 378 bytes of raw binary data
// Requires BigInt support in the browser's or other JS engine
// Created by Luxferre in 2023, released into public domain
// Made in Ukraine

Telememer = (params => {
  var nameAlphabet = params[0],
      digitAlphabet = params[1],
      indexAlphabet = params[2],
      nameLen = params[3],
      effectiveNameLen = nameLen - 1, // the first character is used for part indexing because of the autosort feature
      numLen = params[4],
      nameAlphaLen = nameAlphabet.length, // length of the name alphabet
      digitAlphaLen = digitAlphabet.length, // length of the digit alphabet
      telememoSize = indexAlphabet.length, // overall size of the telememo memory (determined by the length of the index alphabet)
      namePartBits = 0 | (effectiveNameLen * Math.log2(nameAlphaLen)), // bit length we can encode in the name part
      digitPartBits = 0 | (numLen * Math.log2(digitAlphaLen)), // bit length we can encode in the number part
      recordBits = namePartBits + digitPartBits, // bit length we can encode in the whole record
      maxBits = recordBits * telememoSize, // maximum storage capacity in bits
      // universal base conversion methods
      toBase = (number, radix, digits) => {
        if(number === 0) return digits[0]
        var a = []
        number = BigInt(number)
        radix = BigInt(radix)
        while(number !== 0n) {
          a.unshift(digits[Number(number % radix)])
          number = number/radix
        }
        return a.join('')
      },
      fromBase = (number, radix, digits) => {
        number = ''+number
        if(number === digits[0]) return 0
        number = number.split('')
        var v = 0n
        radix = BigInt(radix)
        while(number.length)
          v = v*radix + BigInt(digits.indexOf(number.shift()))
        return v
      },
      // record part conversion methods
      valToName = n => toBase(n, nameAlphaLen, nameAlphabet).padStart(effectiveNameLen, nameAlphabet[0]),
      valToDigits = n => toBase(n, digitAlphaLen, digitAlphabet).padStart(numLen, digitAlphabet[0]),
      binBitNorm = (x, n) => { // convert a number to byte- or other bit-number aligned binary value
        var raw = x.toString(2)
        return raw.padStart(n * Math.ceil(raw.length / n), '0')
      }

  return {
    encode: data => { // (Uint8)Array => [records], where a record is ['name', 'number']
      var bitstream = [], dl = data.length, i, pos, records = []
      for(i=0;i<dl;i++) // create a bitstream from our data
        binBitNorm(data[i], 8).split('').forEach(x => {bitstream.push(+x)})
      var bitLen = bitstream.length
      if(bitLen > maxBits) { // truncate the input stream if it exceeds the full capacity 
        bitLen = maxBits
        bitstream = bitstream.slice(0, maxBits)
      }
      var recLen = Math.ceil(bitLen / recordBits) // message length in full records
      for(i=0,pos=0;i<recLen;i++) { // iterate over bit sets
        var rec = []
        dl = BigInt('0b'+bitstream.slice(pos, pos+namePartBits).join('').padEnd(namePartBits, '0'))
        rec.push(indexAlphabet[i] + valToName(dl))
        pos += namePartBits
        dl = BigInt('0b'+bitstream.slice(pos, pos+digitPartBits).join('').padEnd(digitPartBits, '0'))
        rec.push(valToDigits(dl))
        pos += digitPartBits
        records.push(rec)
      }
      return records
    },
    decode: (recs, expectedLength) => { // [records](, expectedLengthInBytes) => Uint8Array
      var bitstream = [], recLen = recs.length, i, nameval, numval
      for(i=0;i<recLen;i++) { //iterate over records
        nameval = fromBase(recs[i][0].slice(1), nameAlphaLen, nameAlphabet) // drop the index character for the name
        numval = fromBase(recs[i][1], digitAlphaLen, digitAlphabet);
        (binBitNorm(nameval, namePartBits) + binBitNorm(numval, digitPartBits)).split('').forEach(x => {
          bitstream.push(+x)
        })
      }
      var bytes = bitstream.join('').match(/\d{8}/g).map(x => parseInt(x, 2))
      if(expectedLength) bytes = bytes.slice(0, expectedLength)
      return Uint8Array.from(bytes)
    }
  }
})([
  " ABCDEFGHIJKLMNOPQRSTUVWXYZ@!?',.;:()/+-0123456789", // full 50-character range for name
  ' 0123456789()+-', // full 15-character range for number value
  'ABCDEFGHIJKLMNOPQRSTUVWXY12345', // 30-character range for index position
  8, // name field length
  16 // number field length
])

FYI. this library has been ported to Python 3 as a standalone CLI app: Databankr