mkadlec has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to store the actual files I am reading from a directory into a database. The files are mostly wav and tif format files, I think hex format would be the best method. I don't know how to convert files into hex format using Perl, does anyone know how this could be done?

Replies are listed 'Best First'.
Re: Hex format conversion in Perl
by suaveant (Parson) on Apr 19, 2001 at 18:49 UTC
    I know that in MySQL you can actually store binary data directly in blob fields... however I also know that whenever someone asks they are always told it is better to keep the items in files and just store their location in the database...
                    - Ant
[reply]
      Most SQL92 compliant databases have a BLOB type which will store binary data.
      I wish I could ++ you again, storing the path to the file on disk is 99.999% of the time a Good Thing

      -- Dave
[reply]
        Yeah... there have been times I've wanted to give people a better vote... since there are some answers that solve the problem, and some that solve the problem while teaching... or some that just have lots of good points, etc...
        oh well... this site is quite well set up as it is, which I'm sure has taken A LOT of hard work. :)
                        - Ant
[reply]
Re: Hex format conversion in Perl
by jeroenes (Priest) on Apr 19, 2001 at 18:44 UTC
    Various ways. But perl doesn't care if you mess with strings or hexs. 
    #reading
local $/ = undef;  #trick to read all data in one swoop
open FILE, $myfile;
my $hex = <FILE>;

#or writing:
open FILE, ">$myfile";
print FILE $tiff_data;

    [download]
    If you are on win32, check binmode.

    Hope this helps,

    Jeroen
    "We are not alone"(FZ)

[reply]
[d/l]
      jeroenes, did you forget the hex conversion?
      (his reply is now below)
      # reading (for example, a gif)
local $/ = undef;
open FILE, $file;
binmode(FILE); # needed for win32
$gif = <FILE>;
$hexgif = unpack ("H*", $gif); # convert gif to hex string

# printing
$gif = pack ("H*", $hexgif); # convert hex string back to binary data
print "Content-type: image/gif\n\n";
binmode(STDOUT);
print $gif;

      [download]

      Update: jeroenes is right about the size consideration. You asked for hex so that's what this code does. But a hex string is double the size of the binary data is encodes. Here are the results of some different methods for encoding binary data as text:

      bytesformat% of original
      5008 original jpeg 100.00%
      10016 hex string 200.00%
      6904 uuencoded 137.86%
      6768 base64 135.14%
      6706 zlib/uuencoded 133.91%
      6574 zlib/base64 131.27%
      4865 zlib (binary) 97.14%

[reply]
[d/l]
        Not forgotten.
        IMHO, you don't need that conversion at all, unless there is another reason/problem. Perl has no trouble with a string like the first $gif in your code.

        Why would you want an extra conversion step? Maybe you like to dump the hex-string on a terminal, readible to the human eye? Insert it in an e-mail (base64 would be better in that case)? Does the database only accept ASCII strings (BerkeleyDB eg does accept them)?

        But if you just want to redirect the data in a perlish way, just keep with the unconverted 1-byte wide strings.

        Jeroen
        "We are not alone"(FZ)
        Update: epoptai CB'd me an alternative explanation of the posting, that makes more sense. His code will do. But, consider pack 'u*', $gif;, CGIPack or MIME::Base64 to pack your strings, as that shortens the strings somewhat.

[reply]
[d/l]

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