[bb] Base 64 Encoder/Decoder Functions by Andy_A [ 1+ years ago ]

[BlitzBot]

Title : Base 64 Encoder/Decoder Functions
Author : Andy_A
Posted : 1+ years ago

Description : Mangus wrote the Encoding Function and left this as an exercise to write the Decoding Function.  Here it is.

Code :

Code (blitzbasic) Select Expand

;########     BASE 64 ENCODER by Mangus     ###########
;########   BASE 64 DECODER by Andy Amaya   ###########

org$ = "I have detected a Fatal Mouse Error - shall I spank the cat?"
Print "String to Encode:"
Print org$
Print""

Print "Encoded string:"
Print b64enc$(org$) ;little example ;)
Print""


msg$ = b64enc$(org$)
Print "Decoded string:"
Print b64dec$(msg$)
Input()


Function b64enc$(a$)
b64$="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
m$=""
f$=""
largo=Len(a$)
;Encode a$ into one long string of bits
cx$=""
For encode=1 To largo
x$=Mid$(a$,encode,1)  ;get one char at a time
Tx=Asc(x$)            ;Tx = ASCII code
b$=Bin$(Tx)           ;convert Tx into string of 32 bits
b$=Right$(b$,8)       ;get the right most 8 bits out of the 32 bits
cx$=cx$+b$            ;add string of 8 bits to cx$
Next
;largo = number of bits stored in cx$
largo=Len(cx$)
For encode=1 To largo Step 6
x$=Mid$(cx$,encode,6)
bbb=Len(x$)
bbbx=6-bbb ;check for 6 bits
;If not full 6 bits at end of bit string, then add "=" to end of encoded string
If bbbx>0 Then
f$="="
EndIf
x$=x$ + Left$("00000000",bbbx) ;pad with zeroes to make 6 bits
res=0
For y=0 To 5
by  = Asc(Mid$(x$, 6-y, 1)) - 48 ;get bits from right to left (least significant to most)
res = res + ( 2^y * by) ;raise to power of 2 and add to res (result)
Next
m$=m$+Mid$(b64$,res+1,1)+f$
Next
Return m$
End Function

Function b64dec$(a$)
b64$="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
m$=""
f$=""
length = Len(a$)
cx$ = ""
If Right$(a$,1) = "=" Then length = length - 2: flag = 1

For decode = 1 To length
x$ = Mid$(a$,decode,1)
pos = Instr(b64$,x$)-1
b$ = Bin$(pos)
b$ = Right$(b$,6)
cx$ = cx$ + b$
Next

If flag = 1 Then
numBits = 6 * (Len(a$)-2)
rmdr = (Floor(numBits/8)+1)*8-numBits
oddChar$ = Mid$(a$,Len(a$)-1,1)
pos =Instr(b64$, oddChar$)-1
b$ = Right$(Bin$(pos),6)
b$ = Left$(b$,rmdr)
cx$ = cx$ + b$
End If

length = Len(cx$)

For decode = 1 To length Step 8
b$ = Mid$(cx$,decode,8)
res = 0
For y = 0 To 7
bit =Asc( Mid$(b$,8-y,1)) - 48
If bit <> 0 Then
res = res Or (2^y * bit)
End If
Next
m$ = m$ + Chr$(res)
Next
Return m$
End Function

Comments :


mangus(Posted 1+ years ago)

 Great job Andy... I am thinking that you were needing this for the same purpose that me? (making an emailer?)


Andy_A(Posted 1+ years ago)

 Actually did this because it seemed to me to be an open challenge by Mangus to complete the code, so I did. Blitz was also at the time very new to me, this provided a good opportunity to investigate Blitz code syntax.The more I think about it, could also be used for a creating a Blitz "PostIt" type program.Glad you can find a good use for it.


Andy_A(Posted 1+ years ago)

 It took me a while to notice you're the guy who wrote the encoding function. Thanks!Could I have your permission to post the encoding function on the BlitzCoder website?


mangus(Posted 1+ years ago)

 Of course.. consider it yours! make this an open source world oh yeah!


virtlands(Posted 1+ years ago)

 <bookmarked>


Andy_A(Posted 1+ years ago)

 @VirtlandsI would recommend using the encoding and decoding functions from this post <a href="http://www.blitzmax.com/codearcs/codearcs.php?code=3026" target="_blank">http://www.blitzmax.com/codearcs/codearcs.php?code=3026</a>as it's much more efficient (faster).