Hey, I'm kinda tickled my little area has some traffic. 
@mnrvovrfc: Good suggestion adding the DIM line. The goal is to output a portable FUNCTION people can add to any program easy, and that will help make it so.
I admit I haven't used OPTION EXPLICIT before, and didn't really understand what it was for until I heard Fellippe talk about it in a podcast. I think it will help me prevent coding errors, so I'm going to get to know it. Also, I am very bad about naming variables well (I rush coding) so that is something I will try to work on.
I think these Base91 functions are working without errors. I scrapped the ones I came up with because they kept corrupting data, so I went back to these I adapted from sources on the internet in another language. These seem to work ok.
These haven't been speed up using the MID$ technique yet, will do that next. Will have to do something different than the Base85 function do. Since Base91 encoded output size is not 100% predictable like Base64 & Base85 output is (it can fluctuate according to input data), I will have to save the original input size in the B91 encoded data, and then strip it out during decoding.
- Dav
@mnrvovrfc: Good suggestion adding the DIM line. The goal is to output a portable FUNCTION people can add to any program easy, and that will help make it so.
I admit I haven't used OPTION EXPLICIT before, and didn't really understand what it was for until I heard Fellippe talk about it in a podcast. I think it will help me prevent coding errors, so I'm going to get to know it. Also, I am very bad about naming variables well (I rush coding) so that is something I will try to work on.
I think these Base91 functions are working without errors. I scrapped the ones I came up with because they kept corrupting data, so I went back to these I adapted from sources on the internet in another language. These seem to work ok.
These haven't been speed up using the MID$ technique yet, will do that next. Will have to do something different than the Base85 function do. Since Base91 encoded output size is not 100% predictable like Base64 & Base85 output is (it can fluctuate according to input data), I will have to save the original input size in the B91 encoded data, and then strip it out during decoding.
- Dav
Code: (Select All)
'==========
'BASE91.BAS
'==========
'Base-91 Encoder/Decoder Functions.
'Coded by Dav for QB64-PE 3.8.0, SEP/2023
'(adpated from sources found on the web)
'NOTE: This uses a modified Base-91 character set so code output doesn't
'include symbols that conflict with the QB64-PE forum message posting.
'Unlike Base64 & Base85, Base91 space efficiency changes according to input.
'It is somewhere near 23% percent added to the input source, a wee bit better
'than Base85 which is 25% more, and much better than Base64 which is 33%.
Screen 12
_ControlChr Off
Do
Cls
Color 15, 1: Print "Checking bytes loop -- Hit any key to stop checking ..."
a$ = ""
Print
Color 7, 0: Print "Original:"
bytes = 200 + Int(Rnd * 55)
For i = 0 To bytes
a$ = a$ + Chr$(Int(Rnd * 255))
Next
Print a$
Print Len(a$); "bytes"
Print
Print "Encoded:"
a2$ = Base91Encode$(a$): Print a2$
Print Len(a2$); "bytes"
Print
Print "Decoded:"
a3$ = Base91Decode$(a2$): Print a3$
Print Len(a3$); "bytes"
Print
If Len(a$) <> Len(a3$) Then Color 12, 0: Print "Size don't match!"; t: End
If a$ <> a3$ Then Color 12, 0: Print "Bytes don't match!"; t: End
_Display
_Limit 15
If _KeyHit Then Exit Do
loopcount = loopcount + 1
bytecount = bytecount + bytes
Loop
Print "Checked"; loopcount; "loops of"; bytecount; "bytes."
Print "No errors detected."
End
Function Base91Encode$ (in$)
'Build 91 characters to use
For i = 33 To 126
If i <> 34 And i <> 64 And i <> 96 Then Chars$ = Chars$ + Chr$(i)
Next
For i& = 1 To Len(in$)
bits = (bits Or (Asc(Mid$(in$, i&, 1)) * (2 ^ nbits)))
nbits = nbits + 8
If nbits > 13 Then
value = bits Mod 8192
If value > 88 Then
bits = (bits \ (2 ^ 13))
nbits = nbits - 13
Else
value = bits Mod 16384
bits = (bits \ (2 ^ 14))
nbits = nbits - 14
End If
out$ = out$ + Mid$(Chars$, (value Mod 91) + 1, 1) + Mid$(Chars$, (value \ 91) + 1, 1)
End If
Next
If nbits > 0 Then
out$ = out$ + Mid$(Chars$, (bits Mod 91) + 1, 1)
If nbits > 7 Or bits > 90 Then
out$ = out$ + Mid$(Chars$, (bits \ 91) + 1, 1)
End If
End If
Base91Encode$ = out$
End Function
Function Base91Decode$ (in$)
'Build 91 characters to use
For i = 33 To 126
If i <> 34 And i <> 64 And i <> 96 Then Chars$ = Chars$ + Chr$(i)
Next
value = -1
For i& = 1 To Len(in$)
ascii = InStr(Chars$, Mid$(in$, i&, 1)) - 1
If value < 0 Then
value = ascii
Else
value = value + (ascii * 91)
bits = bits Or _ShL(value, nbits)
nbits = nbits + 13 + (((value And 8191) <= 88) * -1)
Do Until (nbits > 7) = 0
out$ = out$ + Chr$(bits And 255)
bits = _ShR(bits, 8)
nbits = nbits - 8
Loop
value = -1
End If
Next
If (value + 1) Then
out$ = out$ + Chr$((bits Or _ShL(value, nbits)) And 255)
End If
Base91Decode$ = out$
End Function