Perl Guru Forums: Perl Programming Help: Advanced: Problem converting 64bit binary (qword) to float (Win32)

I need to convert 64bit (8byte) binary data to double-precision floating point.

I need this: 0100000001001001000000000000000000000000000000000000000000000000
To convert to floating point 50.00

I tried unpack, but it's built-in float is only 32bit. See the test code below where unpack gives the same results for all 64 bits as when only using the first 32 bits.

Code

my $binary64 = '0100000001001001000000000000000000000000000000000000000000000000'; # Hex: 4049000000000000 Decimal: 50 
my $unpacked64 = unpack('d',$binary64); 
print "64 Bits: $binary64\n"; 
print "Unpacked with 'd': $unpacked64\n\n"; 
 
# Compare to same string as above, but truncated to 32bits 
my $binary32 = substr($binary64,0,32); # Hex: 40490000 
my $unpacked32 = unpack('d',$binary32); 
print "32 Bits: $binary32\n"; 
print "Unpacked with 'd': $unpacked32\n";

OUTPUT:

Code

Bits: 0100000001001001000000000000000000000000000000000000000000000000 
Unpacked with 'd': 1.39804328609537e-076 
 
Bits: 01000000010010010000000000000000 
Unpacked with 'd': 1.39804328609537e-076

(The 64bit number should be 50 in decimal)

I'm using Bit::Vector for my 64bit long conversions, but that doesn't support floats.

While Math::BigInt supports binary input (just preface the binary string with '0b'), that doesn't work for Math::BigFloat

Code

my $binary64 = '0100000001001001000000000000000000000000000000000000000000000000'; 
 
use Math::BigInt; 
my $bigInt = Math::BigInt->new('0b'.$binary64); 
print "64bits as INT: $bigInt\n"; 
 
use Math::BigFloat;  
my $bigFloat = Math::BigFloat->new('0b'.$binary64); 
print "64bits as Float: $bigFloat\n";

OUTPUT:

Code

64bits as INT: 4632233691727265792 
Can't use an undefined value as a SCALAR reference at c:/Perl/lib/Math/BigFloat.pm line 177.

Does anyone have any suggestions? I just hit a brick wall on my project.


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