How to convert an integer to bytes and back to an integer.
# argument: short integer to convert to two bytes
# return: two bytes
sub short_to_bytes
{
    local @_ = unpack("C*",pack("L",shift));
    (shift, shift);
}

# argument: two bytes to convert into an integer
# return: short integer
sub bytes_to_short
{

    my $res = 0;
    $res |= $bytes[1] & 0xFF;
    $res <<= 8;
    $res |= $bytes[0] & 0xFF;
    return $res;
}

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Re: Int ->Bytes -> Int
by ikegami (Patriarch) on Sep 03, 2007 at 07:20 UTC
    bytes_to_short(short_to_bytes($x)) is not equal to $x on all platforms. Use v instead. (Using "L" to convert shorts is silly anyway.)

    Furthermore, "short" is a very ambiguous term. It doesn't necessarily mean 16 bits, and it definitely doesn't imply unsigned (as your code expects). 

    sub uint16_to_bytes {
   my ($int) = @_;
   return unpack('C2', pack('v', $int));
}

sub bytes_to_uint16 {
   my ($lo, $hi) = @_;
   return unpack('v', pack('C2', $lo, $hi));
}

sub int16_to_bytes {
   my ($int) = @_;
   return unpack('C2', pack('v', unpack('S', pack('s', $int))));
}

sub bytes_to_int16 {
   my ($lo, $hi) = @_;
   return unpack('s', pack('S', unpack('v', pack('C2', $lo, $hi))));
}

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Re: Int ->Bytes -> Int
by bruceb3 (Pilgrim) on Sep 03, 2007 at 06:28 UTC
    Cool. Is there a line missing bytes_to_short subroutine? Where is @bytes initialized?
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