Re^2: how to search binary file

No need to slurp the whole thing. Just set $/ to whatever you want to look for and see if it chomps.

my $fi = "foo\xd9bar\xd9baz\xd9nothing";
open IN, '<', \$fi or die "Die fi!\n";
$/ = "\xd9";
while (<IN>) {
  print chomp() ? "Found after $_\n" : "Not after $_\n";
}
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Re^3: how to search binary file by ikegami (Patriarch) on Apr 25, 2005 at 17:18 UTC
Of course, if the pattern is not found (or found late), your solution still slurps the whole file. The following solution keeps at most {buffer size}+{pattern length)-1 bytes of the file in memory at a time. my $pattern = "\xFF\xD9"; open(FILE, "< $file") or die("Unable to open input file: $!\n"); binmode(FILE); # Disable "\n" translation. $/ = \4096; # Arbitrary buffer size. my $block; my $partial = ''; my $base = 0; my $matches = 0; while ($block = <FILE>) { my $lookbehind = $partial . $block; my $pos = -1; for (;;) { $pos = index($lookbehind, $pattern, $offset+1); last if $pos == -1; print("Found a match at ", $base+$pos-length($partial), "\n"); $matches++; } $partial = substr($block, 1 - length($pattern)); $base += length($block); } if ($matches) { print("Found $matches matches.\n"); } else { print("Pattern not found.\n"); } [download] Will report overlapping matches. Untested.	[reply] [d/l]

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Re^3: how to search binary file
by ikegami (Patriarch) on Apr 25, 2005 at 17:18 UTC

Of course, if the pattern is not found (or found late), your solution still slurps the whole file. The following solution keeps at most {buffer size}+{pattern length)-1 bytes of the file in memory at a time.

my $pattern = "\xFF\xD9";

open(FILE, "< $file")
or die("Unable to open input file: $!\n");

binmode(FILE);   # Disable "\n" translation.

$/ = \4096;      # Arbitrary buffer size.

my $block;
my $partial = '';
my $base = 0;

my $matches = 0;

while ($block = <FILE>) {
   my $lookbehind = $partial . $block;

   my $pos = -1;

   for (;;) {
      $pos = index($lookbehind, $pattern, $offset+1);
      last if $pos == -1;

      print("Found a match at ", $base+$pos-length($partial), "\n");
      $matches++;
   }

   $partial = substr($block, 1 - length($pattern));
   $base += length($block);
}

if ($matches) {
   print("Found $matches matches.\n");
} else {
   print("Pattern not found.\n");
}
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Will report overlapping matches.

Untested.

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[d/l]