Document the BN library.

1 files changed, 64 insertions, 0 deletions

diff --git a/doc/crypto/BN_set_bit.pod b/doc/crypto/BN_set_bit.pod
new file mode 100644
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+++ b/doc/crypto/BN_set_bit.pod
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+=pod
+
+=head1 NAME
+
+BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift,
+BN_lshift1, BN_rshift, BN_rshift1 - Bit operations on BIGNUMs
+
+=head1 SYNOPSIS
+
+ #include <openssl/bn.h>
+
+ int BN_set_bit(BIGNUM *a, int n);
+ int BN_clear_bit(BIGNUM *a, int n);
+
+ int BN_is_bit_set(const BIGNUM *a, int n);
+
+ int BN_mask_bits(BIGNUM *a, int n);
+
+ int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
+ int BN_lshift1(BIGNUM *r, BIGNUM *a);
+
+ int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
+ int BN_rshift1(BIGNUM *r, BIGNUM *a);
+
+=head1 DESCRIPTION
+
+BN_set_bit() sets bit B<n> in B<a> to 1 (C<a|=(1E<lt>E<lt>n)>). The
+number is expanded if necessary.
+
+BN_clear_bit() sets bit B<n> in B<a> to 0 (C<a&=~(1E<lt>E<lt>n)>). An
+error occurs it B<a> is shorter than B<n> bits.
+
+BN_is_bit_set() tests if bit B<n> in B<a> is set.
+
+BN_mask_bits() truncates B<a> to an B<n> bit number
+(C<q&=~((~0)E<gt>E<gt>n)>).  An error occurs it B<a> already is
+shorter than B<n> bits.
+
+BN_lshift() shifts B<a> left by B<n> bits and places the result in
+B<r> (C<r=a*2^n>). BN_lshift1() shifts B<a> left by one and places
+the result in B<r> (C<r=2*a>).
+
+BN_rshift() shifts B<a> right by B<n> bits and places the result in
+B<r> (C<r=a/2^n>). BN_rshift1() shifts B<a> right by one and places
+the result in B<r> (C<r=a/2>).
+
+=head1 RETURN VALUES
+
+BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
+
+All other functions return 1 for success, 0 on error. The error codes
+can be obtained by ERR_get_error(3).
+
+=head1 SEE ALSO
+
+bn(3), BN_num_bytes(3), BN_add(3)
+
+=head1 HISTORY
+
+BN_set_bit(), BN_clear_bit(), BN_is_bit_set(), BN_mask_bits(),
+BN_lshift(), BN_lshift1(), BN_rshift(), and BN_rshift1() are available
+in all versions of SSLeay and OpenSSL.
+
+=cut