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

Hi Monks, I have a file that is mixed with ascii text and binary. The binary part of the file is delimited by "Binary:\n". Then there is binary data that must be read 64 bits at a time. The binary data is too large to be split into a separate file or copy, so I would like to do this in one swoop. The following code does not work, it appears as if I cannot switch to binmode once I encounter the binary section of the file? Again, pretend that the binary portion is large so this needs to be done efficiently. Thanks in advance! 

#!/usr/local/bin/perl
use strict;
use warnings;

my $raw_file="spectrebin.raw";
open (FILE,$raw_file);

foreach my $line (<FILE>) {
   if ($line=~/^Binary:/) {
      #Switch to binary mode
 
      #NOTE: If you comment this line in, 
      #   it works but starts reading the file from the 
      #   start, which I do not want.  I want it to 
      #   read only the binary portion
      #open (FILE,$raw_file);  

      binmode(FILE) or die "ERROR> Could not read binary file";
      my $buffer;
      while ((read (FILE, $buffer, 64))!=0) {
         my $binary = unpack("B64",$buffer);
         printf "Binary: $binary\n";
      }
      #Do not read the binary part as ascii
      last;
   } else {
      #the ascii part
      printf "ASCII: $line";
   }
}

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Re: Mixed text and binary file
by davido (Cardinal) on Feb 20, 2014 at 20:28 UTC

    Set binmode at the beginning, and set $/ = 'Binary:';. Do a single read from the filehandle with $text = <FILE>. Then set $/=\64;, and subsequent reads with $chunk = <FILE> will be 64 bytes at a chunk.

    Another approach is to use tell once you've found the exact location of Binary:, then seek and read from that point. In this case, I would still start out by setting $/ = 'Binary:', so that I wouldn't have to worry about counting backwards from the next apparent newline to 'Binary:'.


    Dave

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[d/l]
[select]

      Thanks! Based on your feedback this works. It never ceases to amaze me what perl can do! I'm first preserving the ASCII portion of the file other purposes. 

      #!/usr/local/bin/perl
use strict;
use warnings;

my $raw_file="spectrebin.raw";

open (FILE,$raw_file);

foreach my $line (<FILE>) {
   if ($line=~/^Binary:/) {
      #Do not read the binary part as ascii
      printf "ASCII: $line";
      last;
   } else {
      #the ascii part
      printf "ASCII: $line";
   }
}
close(FILE);

open (FILE,$raw_file);  
binmode(FILE) or die "ERROR> Could not read binary file";

$/ = "Binary:\n";
my $text = <FILE>;

my $buffer;
while ((read (FILE, $buffer, 64))!=0) {
   my $binary = unpack("B64",$buffer);
   printf "Binary: $binary\n";
}
close(FILE);

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[reply]
[d/l]
        It never will cease to amaze you ... what Perl can do ... This language has been called a Swiss-Army Knife, and it deserves the accolade.
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