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(tye)Re: 64 bit Integer anyone?

by tye (Cardinal)
on Oct 12, 2000 at 00:46 UTC ( #36314=note: print w/ replies, xml ) Need Help??


in reply to 64 bit Integer anyone?

The "q" format for pack()/unpack() is only supported if your copy of perl was compiled with quadword support (only available on some platforms).

But just about any version of Perl supports 53-bit integers which is often plenty, even when dealing with 64-bit data.

#!/usr/bin/perl -wl use strict; my $little; BEGIN { $little= unpack "C", pack "S", 1; } sub quad { my( $str )= @_; my $big; if( ! eval { $big= unpack( "Q", $str ); 1; } ) { my( $lo, $hi )= unpack "LL", $str; ( $hi, $lo )= ( $lo, $hi ) if ! $little; $big= $lo + $hi*( 1 + ~0 ); if( $big+1 == $big ) { warn "Forced to approximate!\n"; } } return $big; } my @quads= ( "\xff\xff\xff\xff\xff\xff\xff\xff", "\x00\x3f\xff\xff\xff\xff\xff\xff", "\x00\x1f\xff\xff\xff\xff\xff\xff" ); if( $little ) { for( @quads ) { $_= reverse $_; } } for( @quads ) { print quad( $_ ); } __END__ This prints: Forced to approximate! 1.84467440737096e+019 Forced to approximate! 1.8014398509482e+016 9.00719925474099e+015

Note that assumes an unsigned 64-bit integer.

        - tye (but my friends call me "Tye")


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(tye)Re2: 64 bit Integer anyone?
by tye (Cardinal) on Oct 12, 2000 at 01:08 UTC

    Okay, I think I have signed quads working...

    #!/usr/bin/perl -w use strict; my $little; BEGIN { $little= unpack "C", pack "S", 1; } sub quad { my( $str )= @_; my $big; if( ! eval { $big= unpack( "Q", $str ); 1; } ) { my( $lo, $hi )= unpack "LL", $str; ( $hi, $lo )= ( $lo, $hi ) if ! $little; $big= $lo + $hi*( 1 + ~0 ); if( $big+1 == $big ) { warn "Forced to approximate!\n"; } } return $big; } sub squad { my( $str )= @_; my $big; if( ! eval { $big= unpack( "Q", $str ); 1; } ) { my( $lo, $hi )= unpack $little ? "Ll" : "lL", $str; ( $hi, $lo )= ( $lo, $hi ) if ! $little; if( $hi < 0 ) { $hi= ~$hi; $lo= ~$lo; $big= -1 -$lo - $hi*( 1 + ~0 ); } else { $big= $lo + $hi*( 1 + ~0 ); } if( $big+1 == $big ) { warn "Forced to approximate!\n"; } } return $big; } my @quads= ( "\xff\xff\xff\xff\xff\xff\xff\xff", "\x00\x3f\xed\xcb\xa9\x87\x65\x43", "\x00\x1f\xff\xff\xff\xff\xff\xff" ); if( $little ) { for( @quads ) { $_= reverse $_; } } $|= 1; push @quads, ~$quads[1], ~$quads[2]; for( @quads ) { print quad( $_ ), "\n"; print squad( $_ ), "\n\n"; } if( quad($quads[2]) == -1 - squad($quads[4]) ) { print "two's complement works!\n"; } __END__ This prints: Forced to approximate! 1.84467440737096e+019 -1 Forced to approximate! 1.79943825111381e+016 Forced to approximate! 1.79943825111381e+016 9.00719925474099e+015 9.00719925474099e+015 Forced to approximate! 1.84287496911984e+019 Forced to approximate! -1.79943825111381e+016 Forced to approximate! 1.84377368744548e+019 -9.00719925474099e+015 two's complement works!

    Though, squad() seems overly convoluted. Improvements welcome.

            - tye (but my friends call me "Tye")

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