From: alexander <alexander@...>
Date: 2007-02-09T18:20:28+09:00
Subject: Re: Problem with Base64 decoding

hi there,
thank you for your tips!

and indeed using write instead of puts i atleast got the filesize right.
sadly everything else is still wrong.

i think the problem is definitely in the decoding, but i don�t even know
where to start there since the resulting files vary to a great degree.
inspecting a hexdump of both decoded files show that they are not even
remotely the same.

right now i use a php script that i call with system. it�s kind of an
ugly solution, but at least it works ;)

i will keep trying though to get a 100% ruby solution to this problem.

kind regards and thanks again,

alexander


Jan Svitok wrote:
> On 1/29/07, alexander <alexander@fork.de> wrote:
> 
>> hi there,
>> last time i accidentely posted this question as a reply to another one..
>> i�m really sorry for that. i will not make that mistake again.
>>
>> so here�s my question again in a fresh new thread :)
>>
>> i�m having a small problem with base64 decoding a string.
>> i�m porting a php script over to ruby and the decoding gives me
>> different results in ruby and in php. the problem is that the php
>> results works for the processing i do afterwards while the ruby version
>> doesn�t.
>> here�s the scripts in question:
>>
>> php:
>> <?
>>
>>         $bytes = file_get_contents("test.rgb");
>>         $bitmap = base64_decode($bytes);
>>
>>         $header = "";
>>         $header .= "\xFF\xFE";
>>         $header .= pack("n2",120,97);
>>         $header .= "\x01";
>>         $header .= "\xFF\xFF\xFF\xFF";
>>
>>         $header .= $bitmap;
>>
>>         file_put_contents("test_php.gd",$header);
>> ?>
>>
>> ruby:
>> require 'rubygems'
>> require 'fileutils'
>> require 'base64'
>>
>> all_bytes = Base64.decode64(IO.read("test.rgb"))
>>
>> bitmap = "\xFF\xFE"
>> bitmap << [120,97].pack("n2")
>> bitmap << "\x01"
>> bitmap << "\xFF\xFF\xFF\xFF"
>> bitmap << all_bytes
>>
>> File.new("test_ruby.gd","w").puts(bitmap)
>>
>> the ruby version is one byte shorter.
>>
>> i�m probably missing something rather obvious here, but any pointers to
>> how i can make the ruby output be like the php output would be greatly
>> appreciated  :)
>>
>> i�ve uploaded the test.rgb file i�m using to here:
>>
>> http://rss.fork.de/test.rgb if that�s even needed  :)
> 
> 
> Hi,
> 
> 1. have a look at the differences in those two files. By that you
> should be able to tell where's the problem: either in the decoding
> part or in the assembling.
> 
> 2. you are using puts that appends a newline, so it seems to me that
> ruby version is one byte LONGER. if that's the problem, replace puts
> with write.
> 
> 3. File.open("test_ruby.gd","w") {|f| f.puts(bitmap) } should be
> safer, as it doesn't rely on garbage collector for closing the file,
> it is closed immediately after the block finishes. This will be
> helpful when you'll work with large number of files (and you'll run
> out of free descriptors)
> 
> 4. I guess you don't need rubygems nor fileutils for this to work
> (that's ok if you use them for some other code not posted)
>