1: =pod
    2: 
    3: =head1 NAME
    4: 
    5: BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
    6: BN_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: 
   28: BN_bn2bin() converts the absolute value of B<a> into big-endian form
   29: and stores it at B<to>. B<to> must point to BN_num_bytes(B<a>) bytes of
   30: memory.
   31: 
   32: BN_bin2bn() converts the positive integer in big-endian form of length
   33: B<len> at B<s> into a B<BIGNUM> and places it in B<ret>. If B<ret> is
   34: NULL, a new B<BIGNUM> is created.
   35: 
   36: BN_bn2hex() and BN_bn2dec() return printable strings containing the
   37: hexadecimal and decimal encoding of B<a> respectively. For negative
   38: numbers, the string is prefaced with a leading '-'. The string must be
   39: freed later using OPENSSL_free().
   40: 
   41: BN_hex2bn() converts the string B<str> containing a hexadecimal number
   42: to a B<BIGNUM> and stores it in **B<bn>. If *B<bn> is NULL, a new
   43: B<BIGNUM> is created. If B<bn> is NULL, it only computes the number's
   44: length in hexadecimal digits. If the string starts with '-', the
   45: number is negative. BN_dec2bn() is the same using the decimal system.
   46: 
   47: BN_print() and BN_print_fp() write the hexadecimal encoding of B<a>,
   48: with a leading '-' for negative numbers, to the B<BIO> or B<FILE>
   49: B<fp>.
   50: 
   51: BN_bn2mpi() and BN_mpi2bn() convert B<BIGNUM>s from and to a format
   52: that consists of the number's length in bytes represented as a 4-byte
   53: big-endian number, and the number itself in big-endian format, where
   54: the most significant bit signals a negative number (the representation
   55: of numbers with the MSB set is prefixed with null byte).
   56: 
   57: BN_bn2mpi() stores the representation of B<a> at B<to>, where B<to>
   58: must be large enough to hold the result. The size can be determined by
   59: calling BN_bn2mpi(B<a>, NULL).
   60: 
   61: BN_mpi2bn() converts the B<len> bytes long representation at B<s> to
   62: a B<BIGNUM> and stores it at B<ret>, or in a newly allocated B<BIGNUM>
   63: if B<ret> is NULL.
   64: 
   65: =head1 RETURN VALUES
   66: 
   67: BN_bn2bin() returns the length of the big-endian number placed at B<to>.
   68: BN_bin2bn() returns the B<BIGNUM>, NULL on error.
   69: 
   70: BN_bn2hex() and BN_bn2dec() return a null-terminated string, or NULL
   71: on error. BN_hex2bn() and BN_dec2bn() return the number's length in
   72: hexadecimal or decimal digits, and 0 on error.
   73: 
   74: BN_print_fp() and BN_print() return 1 on success, 0 on write errors.
   75: 
   76: BN_bn2mpi() returns the length of the representation. BN_mpi2bn()
   77: returns the B<BIGNUM>, and NULL on error.
   78: 
   79: The error codes can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
   80: 
   81: =head1 SEE ALSO
   82: 
   83: L<bn(3)|bn(3)>, L<ERR_get_error(3)|ERR_get_error(3)>, L<BN_zero(3)|BN_zero(3)>,
   84: L<ASN1_INTEGER_to_BN(3)|ASN1_INTEGER_to_BN(3)>,
   85: L<BN_num_bytes(3)|BN_num_bytes(3)>
   86: 
   87: =head1 HISTORY
   88: 
   89: BN_bn2bin(), BN_bin2bn(), BN_print_fp() and BN_print() are available
   90: in all versions of SSLeay and OpenSSL.
   91: 
   92: BN_bn2hex(), BN_bn2dec(), BN_hex2bn(), BN_dec2bn(), BN_bn2mpi() and
   93: BN_mpi2bn() were added in SSLeay 0.9.0.
   94: 
   95: =cut