EDIFACT encoding: 'Return to ASCII mode'-code

[adrianschlatter]

Apparently, toEdifact(msg) encodes the last character in msg as "ASCII" even if it is a valid EDIFACT character.

Example

toEdifact('ABCD') => [240, 4, 32, 223, 69]

• 240: "Start EDIFACT mode" code
• [4, 32, 223] after unpacking 3 bytes to 4 EDIFACT codes result in [1, 2, 3, 31] which means 'A', 'B', 'C', 'Return to ASCII mode'.
• 69: "ASCII" encoding of 'D'

While this works, a more efficient encoding would be [240, 4, 32, 196]:

• 240: "Start EDIFACT mode" code
• [4, 32, 196] unpacked result in [1, 2, 3, 4] which corresponds to 'A', 'B', 'C', 'D'

Code

The culprit is in datamatrix.js/DataMatrix,toEdifact() (note that the if-else systematically skips the last character to place a 31 (="Return to ASCII mode") in front of it):

if (i < l - 1) {
      /* encode char */
      ch = t.charCodeAt(i);
      if (ch < 32 || ch > 94) return []; /* not in set */
} else ch = 31; /* return to ASCII */