Binary to decimal conversion

andreas1234567 has asked for the wisdom of the Perl Monks concerning the following question:

Monks,

I have difficulties converting data on a binary format to decimal numbers related to this node. I suspect the number are encoded using a float. I'm able to see what the results should be using a third-party tool.

The number should perform as follows:

3F F0 00 00 00 00 00 00 should yield 1.
40 59 00 00 00 00 00 00 should yield 100.
41 33 1A 9D 00 00 00 00 should yield 1251997.

What kind of conversion of unpack trickery am I in search for?

A hexdump of the source file is available on my pad (relax it's only 192 bytes).

Update: It seems like this does the trick (updated as shown by Anonymous Monk):

# read number: 8 bytes, return decimal value
sub getnumber {
  my $buffer = undef;
  my $num = read($FH, $buffer, 8);
  return unpack 'd*', reverse $buffer;
}
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Update: pfaut++ and Fletch++ for good advice to stubborn monk.

--
Andreas

Comment on Binary to decimal conversion Select or Download Code

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Re: Binary to decimal conversion
by Anonymous Monk on Dec 11, 2007 at 10:19 UTC

return unpack 'd*', reverse $buffer;
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Re^2: Binary to decimal conversion

by andreas1234567 (Vicar) on Dec 11, 2007 at 10:34 UTC

read

reverse

--
Andreas

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Re^3: Binary to decimal conversion

by pfaut (Priest) on Dec 11, 2007 at 11:48 UTC

From reverse

reverse LIST
      In list context, returns a list value consisting of the ele-
      ments of LIST in the opposite order.  In scalar context, con-
      catenates the elements of LIST and returns a string value with
      all characters in the opposite order.

90% of every Perl application is already written. ⇒

dragonchild

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Re^4: Binary to decimal conversion

by andreas1234567 (Vicar) on Dec 11, 2007 at 11:57 UTC

Re^5: Binary to decimal conversion

by Fletch (Bishop) on Dec 11, 2007 at 13:43 UTC

Some notes below your chosen depth have not been shown here

Re: Binary to decimal conversion
by Anonymous Monk on Dec 11, 2007 at 09:24 UTC

    // read number
    function readNumber(){
        $num = fread($this->buffer, 8);
        $r = "";
        for($byte = 7 ; $byte >= 0 ; $byte--) { // reverse the bytes
            $r .= $num[$byte];
        }
        $ret = unpack("dnum",$r);
        return $ret['num'];
    }
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Re^2: Binary to decimal conversion

by andreas1234567 (Vicar) on Dec 11, 2007 at 09:45 UTC

here

153    // read number
154    function readNumber(){
155      $num = fread($this->buffer, 8);
156      $r = "";
157      for($byte = 7 ; $byte >= 0 ; $byte--) { // reverse the bytes
158        $r .= $num[$byte];
159      }
160      $ret = unpack("dnum",$r);
161      return $ret['num'];
162    }
[download]

PHP

Perl

--
Andreas

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[d/l]

Re^3: Binary to decimal conversion

by Anonymous Monk on Dec 11, 2007 at 10:06 UTC

Translate that to perl, its easy

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