in reply to Fastest byteswap (little endian to big endian (eg. 34127856 -> 12345678)

Before v5.20 the copy on write feature of string was not activated by default. This means that you may win a little time by avoiding to copy the strings in multiple scalars: print $output pack("v*", unpack("n*", scalar <$fh>));

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Re^2: Fastest byteswap (little endian to big endian (eg. 34127856 -> 12345678)
by ikegami (Patriarch) on Apr 14, 2015 at 12:48 UTC
    What copying? No string is copied in that code. COW would not help.
[reply]

      There is in the second method posted by james28909: 

      my $data = do {

    local $/ = undef;
    open (my $fh, "<", $input_file) or die "could not open $input_file
+: $!";
    binmode($fh);
    <$fh>;

};

my $reversed_data = pack( "v*", unpack( "n*", $data ) );

      [download]
      But since it's not copied from one variable to another, it probably makes little difference indeed, I didn't think it through.

[reply]
[d/l]
        That code does copy —note the assignment operator— but I think COW wouldn't help there either because I think the string would be stolen from the temp rather than copied.
[reply]

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