Document the BN library.

doc/crypto/BN_zero.pod

@@ -0,0 +1,52 @@
+=pod
+
+=head1 NAME
+
+BN_zero, BN_one, BN_set_word, BN_get_word - BIGNUM assignment operations
+
+=head1 SYNOPSIS
+
+ #include <openssl/bn.h>
+
+ int BN_zero(BIGNUM *a);
+ int BN_one(BIGNUM *a);
+
+ BIGNUM *BN_value_one(void);
+
+ int BN_set_word(BIGNUM *a, unsigned long w);
+ unsigned long BN_get_word(BIGNUM *a);
+
+=head1 DESCRIPTION
+
+BN_zero(), BN_one() and BN_set_word() set B<a> to the values 0, 1 and
+B<w> respectively.  BN_zero() and BN_one() are macros.
+
+BN_value_one() returns a B<BIGNUM> constant of value 1. This constant
+is useful for use in comparisons and assignment.
+
+BN_get_word() returns B<a>, if it can be represented as an unsigned
+long.
+
+=head1 RETURN VALUES
+
+BN_get_word() returns the value B<a>, and 0xffffffffL if B<a> cannot
+be represented as an unsigned long.
+
+BN_zero(), BN_one() and BN_set_word() return 1 on success, 0 otherwise.
+BN_value_one() returns the constant.
+
+=head1 BUGS
+
+Someone might change the constant.
+
+=head1 SEE ALSO
+
+bn(3), BN_bn2bin(3)
+
+=head1 HISTORY
+
+BN_zero(), BN_one() and BN_set_word() are available in all versions of
+SSLeay and OpenSSL. BN_value_one() and BN_get_word() were added in
+SSLeay 0.8.
+
+=cut