Document the BN library.

[openssl.git] / doc / crypto / BN_bn2bin.pod

diff --git a/doc/crypto/BN_bn2bin.pod b/doc/crypto/BN_bn2bin.pod
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+=pod
+
+=head1 NAME
+
+BN_bn2bin, BN_bin2bn, BN_bn2hex, BN_bn2dec, BN_hex2bn, BN_dec2bn,
+BN_print_fp, BN_print, 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_fp(FILE *fp, BIGNUM *a);
+ int BN_print(BIO *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
+Free()d later.
+
+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_fp() and BN_print() write the hexadecimal encoding of B<a>,
+with a leading '-' for negative numbers, to the B<FILE> or B<BIO>
+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 3-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 ar 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 ERR_get_error(3).
+
+=head1 SEE ALSO
+
+bn(3), err(3), BN_zero(3), ASN1_INTEGER_to_BN(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