openssl/doc/crypto/BN_bn2bin.pod
Richard Levitte 6859cf7459 It makes more sense to refer to specific function manuals than the concept
manual when the specific function is refered to in the current manual text.
This correction was originally introduced in OpenBSD's tracking of OpenSSL.
2002-09-25 13:33:28 +00:00

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=pod
=head1 NAME
BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn - format conversions
=head1 SYNOPSIS
#include <openssl/bn.h>
int BN_bn2bin(const BIGNUM *a, unsigned char *to);
BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
char *BN_bn2hex(const BIGNUM *a);
char *BN_bn2dec(const BIGNUM *a);
int BN_hex2bn(BIGNUM **a, const char *str);
int BN_dec2bn(BIGNUM **a, const char *str);
int BN_print(BIO *fp, const BIGNUM *a);
int BN_print_fp(FILE *fp, const BIGNUM *a);
int BN_bn2mpi(const BIGNUM *a, unsigned char *to);
BIGNUM *BN_mpi2bn(unsigned char *s, int len, BIGNUM *ret);
=head1 DESCRIPTION
BN_bn2bin() converts the absolute value of B<a> into big-endian form
and stores it at B<to>. B<to> must point to BN_num_bytes(B<a>) bytes of
memory.
BN_bin2bn() converts the positive integer in big-endian form of length
B<len> at B<s> into a B<BIGNUM> and places it in B<ret>. If B<ret> is
NULL, a new B<BIGNUM> is created.
BN_bn2hex() and BN_bn2dec() return printable strings containing the
hexadecimal and decimal encoding of B<a> respectively. For negative
numbers, the string is prefaced with a leading '-'. The string must be
freed later using OPENSSL_free().
BN_hex2bn() converts the string B<str> containing a hexadecimal number
to a B<BIGNUM> and stores it in **B<bn>. If *B<bn> is NULL, a new
B<BIGNUM> is created. If B<bn> is NULL, it only computes the number's
length in hexadecimal digits. If the string starts with '-', the
number is negative. BN_dec2bn() is the same using the decimal system.
BN_print() and BN_print_fp() write the hexadecimal encoding of B<a>,
with a leading '-' for negative numbers, to the B<BIO> or B<FILE>
B<fp>.
BN_bn2mpi() and BN_mpi2bn() convert B<BIGNUM>s from and to a format
that consists of the number's length in bytes represented as a 4-byte
big-endian number, and the number itself in big-endian format, where
the most significant bit signals a negative number (the representation
of numbers with the MSB set is prefixed with null byte).
BN_bn2mpi() stores the representation of B<a> at B<to>, where B<to>
must be large enough to hold the result. The size can be determined by
calling BN_bn2mpi(B<a>, NULL).
BN_mpi2bn() converts the B<len> bytes long representation at B<s> to
a B<BIGNUM> and stores it at B<ret>, or in a newly allocated B<BIGNUM>
if B<ret> is NULL.
=head1 RETURN VALUES
BN_bn2bin() returns the length of the big-endian number placed at B<to>.
BN_bin2bn() returns the B<BIGNUM>, NULL on error.
BN_bn2hex() and BN_bn2dec() return a null-terminated string, or NULL
on error. BN_hex2bn() and BN_dec2bn() return the number's length in
hexadecimal or decimal digits, and 0 on error.
BN_print_fp() and BN_print() return 1 on success, 0 on write errors.
BN_bn2mpi() returns the length of the representation. BN_mpi2bn()
returns the B<BIGNUM>, and NULL on error.
The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
=head1 SEE ALSO
L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<BN_zero(3)|BN_zero(3)>,
L<ASN1_INTEGER_to_BN(3)|ASN1_INTEGER_to_BN(3)>,
L<BN_num_bytes(3)|BN_num_bytes(3)>
=head1 HISTORY
BN_bn2bin(), BN_bin2bn(), BN_print_fp() and BN_print() are available
in all versions of SSLeay and OpenSSL.
BN_bn2hex(), BN_bn2dec(), BN_hex2bn(), BN_dec2bn(), BN_bn2mpi() and
BN_mpi2bn() were added in SSLeay 0.9.0.
=cut