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.\" ========================================================================
.\"
.IX Title "Bignum 3pm"
.TH Bignum 3pm "2007-05-20" "perl v5.14.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Crypt::OpenSSL::Bignum \- OpenSSL's multiprecision integer arithmetic
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&  use Crypt::OpenSSL::Bignum;
\&
\&  my $bn = Crypt::OpenSSL::Bignum\->new_from_decimal( "1000" );
\&  # or
\&  my $bn = Crypt::OpenSSL::Bignum\->new_from_word( 1000 );
\&  # or
\&  my $bn = Crypt::OpenSSL::Bignum\->new_from_hex("0x3e8");
\&  # or
\&  my $bn = Crypt::OpenSSL::Bignum\->new_from_bin(pack( "C*", 3, 232 ))
\&
\&  use Crypt::OpenSSL::Bignum::CTX;
\&
\&  sub print_factorial
\&  {
\&    my( $n ) = @_;
\&    my $fac = Crypt::OpenSSL::Bignum\->one();
\&    my $ctx = Crypt::OpenSSL::Bignum::CTX\->new();
\&    foreach my $i (1 .. $n)
\&    {
\&      $fac\->mul( Crypt::OpenSSL::Bignum\->new_from_word( $i ), $ctx, $fac );
\&    }
\&    print "$n factorial is ", $fac\->to_decimal(), "\en";
\&  }
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
Crypt::OpenSSL::Bignum provides access to OpenSSL multiprecision
integer arithmetic libraries.  Presently, many though not all of the
arithmetic operations that OpenSSL provides are exposed to perl.  In
addition, this module can be used to provide access to bignum values
produced by other OpenSSL modules, such as key parameters from
Crypt::OpenSSL::RSA.
.PP
\&\fI\s-1NOTE\s0\fR: Many of the methods in this package can croak, so use eval, or
Error.pm's try/catch mechanism to capture errors.
.SH "Class Methods"
.IX Header "Class Methods"
.IP "new_from_word" 4
.IX Item "new_from_word"
Create a new Crypt::OpenSSL::Bignum object whose value will be the
word given.  Note that numbers represneted by objects created using
this method are necessarily between 0 and 2^32 \- 1.
.IP "new_from_decimal" 4
.IX Item "new_from_decimal"
Create a new Crypt::OpenSSL::Bignum object whose value is specified by
the given decimal representation.
.IP "new_from_hex" 4
.IX Item "new_from_hex"
Create a new Crypt::OpenSSL::Bignum object whose value is specified by
the given hexidecimal representation.
.IP "new_from_bin" 4
.IX Item "new_from_bin"
Create a new Crypt::OpenSSL::Bignum object whose value is specified by
the given packed binary string.  Note that objects created using this
method are necessarily nonnegative.
.IP "zero" 4
.IX Item "zero"
Returns a new Crypt::OpenSSL::Bignum object representing 0
.IP "one" 4
.IX Item "one"
Returns a new Crypt::OpenSSL::Bignum object representing 1
.IP "bless_pointer" 4
.IX Item "bless_pointer"
Given a pointer to a OpenSSL \s-1BIGNUM\s0 object in memory, construct and
return Crypt::OpenSSL::Bignum object around this.  Note that the
underlying \s-1BIGNUM\s0 object will be destroyed (via \fIBN_clear_free\fR\|(3ssl))
when the returned Crypt::OpenSSL::Bignum object is no longer
referenced, so the pointer passed to this method should only be
referenced via the returned perl object after calling bless_pointer.
.Sp
This method is intended only for use by \s-1XSUB\s0 writers writing code that
interfaces with OpenSSL library methods, and who wish to be able to
return a \s-1BIGNUM\s0 structure to perl as a Crypt::OpenSSL::Bignum object.
.SH "Instance Methods"
.IX Header "Instance Methods"
.IP "to_decimal" 4
.IX Item "to_decimal"
Return a decimal string representation of this object.
.IP "to_hex" 4
.IX Item "to_hex"
Return a hexidecimal string representation of this object.
.IP "to_bin" 4
.IX Item "to_bin"
Return a packed binary string representation of this object.  Note
that sign is ignored, so that to bin called on a
Crypt::OpenSSL::Bignum object representing a negative number returns
the same value as it would called on an object representing that
number's absolute value.
.IP "get_word" 4
.IX Item "get_word"
Return a scalar integer representation of this object, if it can be
represented as an unsigned long.
.IP "is_zero" 4
.IX Item "is_zero"
Returns true of this object represents 0.
.IP "is_one" 4
.IX Item "is_one"
Returns true of this object represents 1.
.IP "is_odd" 4
.IX Item "is_odd"
Returns true of this object represents an odd number.
.IP "copy" 4
.IX Item "copy"
Returns a copy of this object.
.IP "add" 4
.IX Item "add"
This method returns the sum of this object and the first argument.  If
only one argument is passed, a new Crypt::OpenSSL::Bignum object is
created for the return value; otherwise, the value of second argument
is set to the result and returned.
.IP "sub" 4
.IX Item "sub"
This method returns the difference of this object and the first
argument.  If only one argument is passed, a new
Crypt::OpenSSL::Bignum object is created for the return value;
otherwise, the value of second argument is set to the result and
returned.
.IP "mul" 4
.IX Item "mul"
This method returns the product of this object and the first argument,
using the second argument, a Crypt::OpenSSL::Bignum::CTX object, as a
scratchpad.  If only two arguments are passed, a new
Crypt::OpenSSL::Bignum object is created for the return value;
otherwise, the value of third argument is set to the result and
returned.
.IP "div" 4
.IX Item "div"
This method returns a list consisting of quotient and the remainder
obtained by dividing this object by the first argument, using the
second argument, a Crypt::OpenSSL::Bignum::CTX object, as a
scratchpad.  If only two arguments are passed, new
Crypt::OpenSSL::Bignum objects is created for both return values.  If
a third argument is passed, otherwise, the value of third argument is
set to the quotient.  If a fourth argument is passed, the value of the
fourth argument is set to the remainder.
.IP "exp" 4
.IX Item "exp"
This method returns the product of this object exponeniated by the
first argument, using the second argument, a
Crypt::OpenSSL::Bignum::CTX object, as a scratchpad.
.IP "mod_exp" 4
.IX Item "mod_exp"
This method returns the product of this object exponeniated by the
first argument, modulo the second argument, using the third argument, a
Crypt::OpenSSL::Bignum::CTX object, as a scratchpad.
.IP "pointer_copy" 4
.IX Item "pointer_copy"
This method is intended only for use by \s-1XSUB\s0 writers wanting to have
access to the underlying \s-1BIGNUM\s0 structure referenced by a
Crypt::OpenSSL::Bignum perl object so that they can pass them to other
routines in the OpenSSL library.  It returns a perl scalar whose \s-1IV\s0
can be cast to a BIGNUM* value.  This can then be passed to an \s-1XSUB\s0
which can work with the \s-1BIGNUM\s0 directly.  Note that the \s-1BIGNUM\s0 object
pointed to will be a copy of the \s-1BIGNUM\s0 object wrapped by the
instance; it is thus the responsiblity of the client to free space
allocated by this \s-1BIGNUM\s0 object if and when it is done with it. See
also bless_pointer.
.SH "AUTHOR"
.IX Header "AUTHOR"
Ian Robertson, iroberts@cpan.org
.SH "SEE ALSO"
.IX Header "SEE ALSO"
perl, \fIbn\fR\|(3ssl)