BN_bn2bin.pod revision 337982 
1=pod
2
3=head1 NAME
4
5BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
6BN_print, BN_print_fp, BN_bn2mpi, BN_mpi2bn - format conversions
7
8=head1 SYNOPSIS
9
10 #include <openssl/bn.h>
11
12 int BN_bn2bin(const BIGNUM *a, unsigned char *to);
13 BIGNUM *BN_bin2bn(const unsigned char *s, int len, BIGNUM *ret);
14
15 char *BN_bn2hex(const BIGNUM *a);
16 char *BN_bn2dec(const BIGNUM *a);
17 int BN_hex2bn(BIGNUM **a, const char *str);
18 int BN_dec2bn(BIGNUM **a, const char *str);
19
20 int BN_print(BIO *fp, const BIGNUM *a);
21 int BN_print_fp(FILE *fp, const BIGNUM *a);
22
23 int BN_bn2mpi(const BIGNUM *a, unsigned char *to);
24 BIGNUM *BN_mpi2bn(unsigned char *s, int len, BIGNUM *ret);
25
26=head1 DESCRIPTION
27
28BN_bn2bin() converts the absolute value of B<a> into big-endian form
29and stores it at B<to>. B<to> must point to BN_num_bytes(B<a>) bytes of
30memory.
31
32BN_bin2bn() converts the positive integer in big-endian form of length
33B<len> at B<s> into a B<BIGNUM> and places it in B<ret>. If B<ret> is
34NULL, a new B<BIGNUM> is created.
35
36BN_bn2hex() and BN_bn2dec() return printable strings containing the
37hexadecimal and decimal encoding of B<a> respectively. For negative
38numbers, the string is prefaced with a leading '-'. The string must be
39freed later using OPENSSL_free().
40
41BN_hex2bn() converts the string B<str> containing a hexadecimal number
42to a B<BIGNUM> and stores it in **B<a>. If *B<a> is NULL, a new
43B<BIGNUM> is created. If B<a> is NULL, it only computes the number's
44length in hexadecimal digits. If the string starts with '-', the
45number is negative.
46A "negative zero" is converted to zero.
47BN_dec2bn() is the same using the decimal system.
48
49BN_print() and BN_print_fp() write the hexadecimal encoding of B<a>,
50with a leading '-' for negative numbers, to the B<BIO> or B<FILE>
51B<fp>.
52
53BN_bn2mpi() and BN_mpi2bn() convert B<BIGNUM>s from and to a format
54that consists of the number's length in bytes represented as a 4-byte
55big-endian number, and the number itself in big-endian format, where
56the most significant bit signals a negative number (the representation
57of numbers with the MSB set is prefixed with null byte).
58
59BN_bn2mpi() stores the representation of B<a> at B<to>, where B<to>
60must be large enough to hold the result. The size can be determined by
61calling BN_bn2mpi(B<a>, NULL).
62
63BN_mpi2bn() converts the B<len> bytes long representation at B<s> to
64a B<BIGNUM> and stores it at B<ret>, or in a newly allocated B<BIGNUM>
65if B<ret> is NULL.
66
67=head1 RETURN VALUES
68
69BN_bn2bin() returns the length of the big-endian number placed at B<to>.
70BN_bin2bn() returns the B<BIGNUM>, NULL on error.
71
72BN_bn2hex() and BN_bn2dec() return a null-terminated string, or NULL
73on error. BN_hex2bn() and BN_dec2bn() return the number of characters
74used in parsing, or 0 on error, in which
75case no new B<BIGNUM> will be created.
76
77BN_print_fp() and BN_print() return 1 on success, 0 on write errors.
78
79BN_bn2mpi() returns the length of the representation. BN_mpi2bn()
80returns the B<BIGNUM>, and NULL on error.
81
82The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
83
84=head1 SEE ALSO
85
86L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<BN_zero(3)|BN_zero(3)>,
87L<ASN1_INTEGER_to_BN(3)|ASN1_INTEGER_to_BN(3)>,
88L<BN_num_bytes(3)|BN_num_bytes(3)>
89
90=head1 HISTORY
91
92BN_bn2bin(), BN_bin2bn(), BN_print_fp() and BN_print() are available
93in all versions of SSLeay and OpenSSL.
94
95BN_bn2hex(), BN_bn2dec(), BN_hex2bn(), BN_dec2bn(), BN_bn2mpi() and
96BN_mpi2bn() were added in SSLeay 0.9.0.
97
98=cut
99