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Reverend



Joined: 24 Aug 2004
Posts: 408
Location: Poland
Reverend
I've had BASE64 masm code on my homepage for some time, but it was just a transcription form C code, and thus just couldn't be really good. There were also some errors.
Finally I rewrote it from scratch. I post here both fasm and masm versions in attachment. There are 3 functions: base64_encode, base64_decode and base64_decode_fast. Two decoding functions, because the first one shares data table with encode func. and the other needs new table of 122 bytes - imho it's worth it, as the second function is significantly faster.
Enjoy! Wink

EDIT:
Newer version in the attachment:
- fixed error when 0 was passed as size
- option to put newline after each n-th character (for example, for MIME encoding)
- only one decoding function (the faster one)
- ignores characters from outside the decoding table


Description: BASE64
Download
Filename: BASE64.ZIP
Filesize: 2.95 KB
Downloaded: 349 Time(s)



Last edited by Reverend on 12 Feb 2007, 19:26; edited 1 time in total
Post 12 Feb 2007, 17:51
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
base64 following which standard (there are more of them)?
supports padding?
what does it do if someone passes length=0?
supports breaking base64 data into multiple lines?
ignores all characters on base64_decode, as defined in RFC 2045?

Wink
Post 12 Feb 2007, 18:01
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Reverend



Joined: 24 Aug 2004
Posts: 408
Location: Poland
Reverend
Asnwers:
- supports padding (ie. pads with '=')
- length = 0
a) encode will work ok
b) decode will fail - I'll have to change it Smile
- no breaking into multiple lines (may add it as an option - TRUE/FALSE flag will change behaviour)
- decode assumes all characters are ok - will have to change it Smile

Thanks for that post vid.
Post 12 Feb 2007, 18:14
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
glad to see you take it seriously. Think about how to report error from procedures (bad base64 data, zero length). If you make these procedures seriously working, i would like to include them to FASMLIB

Quote:
no breaking into multiple lines (may add it as an option - TRUE/FALSE flag will change behaviour)

rather add option for number of chars per line, no breaking if it's zero.
Post 12 Feb 2007, 18:27
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Reverend



Joined: 24 Aug 2004
Posts: 408
Location: Poland
Reverend
New version is in the first, edited post.
As for the error reporting:
- eax contains size of encoded/decoded data - so eax = 0 iff size = 0
- characters outside decoding table are not reported, they are just ignored.

I'd be happy if it shows in FASMLIB Smile
Post 12 Feb 2007, 19:30
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
Quote:
- characters outside decoding table are not reported, they are just ignored.

not all characters should be ignored, only some of them...
Post 12 Feb 2007, 19:35
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Reverend



Joined: 24 Aug 2004
Posts: 408
Location: Poland
Reverend
"Additionally it specifies that any extra-alphabetic characters must be ignored by a compliant decoder" (quote from http://en.wikipedia.org/wiki/Base64)

It was about MIME encoding and generally that was what I wrote BASE64 for.
Post 12 Feb 2007, 19:54
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vid
Verbosity in development


Joined: 05 Sep 2003
Posts: 7105
Location: Slovakia
vid
you are right. But i find it pretty stupid Wink

But do not take wikipedia as reliable source, you must use the RFC next time Wink
Post 12 Feb 2007, 20:29
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r22



Joined: 27 Dec 2004
Posts: 805
r22
Vintage base64 encoding thread
http://board.flatassembler.net/topic.php?t=3063

The algorithm seems to run very fast on pentiums but it doesn't follow a standard implementation (input is null terminated string not sized buffer). But that can be easily changed.
Post 13 Feb 2007, 02:09
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f0dder



Joined: 19 Feb 2004
Posts: 3170
Location: Denmark
f0dder
vid wrote:
you are right. But i find it pretty stupid Wink

But do not take wikipedia as reliable source, you must use the RFC next time Wink


I agree 100% with vid on this. WikiPedia is a great resource and can be used for some initial research, but you shouldn't use use it as an exclusive source of information, and you should always practice source criticism.

_________________
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Post 13 Feb 2007, 07:37
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Reverend



Joined: 24 Aug 2004
Posts: 408
Location: Poland
Reverend
vid, f0dder, I agree with both of you. And I do not take Wikipedia as a omniscient source Smile

r22, thanks for reminding me of this thread. I even joined discussion then and forgot of it Smile
Post 13 Feb 2007, 14:47
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