BN_set_bit.pod 2.0 KB

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  1. =pod
  2. =head1 NAME
  3. BN_set_bit, BN_clear_bit, BN_is_bit_set, BN_mask_bits, BN_lshift,
  4. BN_lshift1, BN_rshift, BN_rshift1 - bit operations on BIGNUMs
  5. =head1 SYNOPSIS
  6. #include <openssl/bn.h>
  7. int BN_set_bit(BIGNUM *a, int n);
  8. int BN_clear_bit(BIGNUM *a, int n);
  9. int BN_is_bit_set(const BIGNUM *a, int n);
  10. int BN_mask_bits(BIGNUM *a, int n);
  11. int BN_lshift(BIGNUM *r, const BIGNUM *a, int n);
  12. int BN_lshift1(BIGNUM *r, BIGNUM *a);
  13. int BN_rshift(BIGNUM *r, BIGNUM *a, int n);
  14. int BN_rshift1(BIGNUM *r, BIGNUM *a);
  15. =head1 DESCRIPTION
  16. BN_set_bit() sets bit B<n> in B<a> to 1 (C<a|=(1E<lt>E<lt>n)>). The
  17. number is expanded if necessary.
  18. BN_clear_bit() sets bit B<n> in B<a> to 0 (C<a&=~(1E<lt>E<lt>n)>). An
  19. error occurs if B<a> is shorter than B<n> bits.
  20. BN_is_bit_set() tests if bit B<n> in B<a> is set.
  21. BN_mask_bits() truncates B<a> to an B<n> bit number
  22. (C<a&=~((~0)E<gt>E<gt>n)>). An error occurs if B<a> already is
  23. shorter than B<n> bits.
  24. BN_lshift() shifts B<a> left by B<n> bits and places the result in
  25. B<r> (C<r=a*2^n>). Note that B<n> must be non-negative. BN_lshift1() shifts
  26. B<a> left by one and places the result in B<r> (C<r=2*a>).
  27. BN_rshift() shifts B<a> right by B<n> bits and places the result in
  28. B<r> (C<r=a/2^n>). Note that B<n> must be non-negative. BN_rshift1() shifts
  29. B<a> right by one and places the result in B<r> (C<r=a/2>).
  30. For the shift functions, B<r> and B<a> may be the same variable.
  31. =head1 RETURN VALUES
  32. BN_is_bit_set() returns 1 if the bit is set, 0 otherwise.
  33. All other functions return 1 for success, 0 on error. The error codes
  34. can be obtained by L<ERR_get_error(3)>.
  35. =head1 SEE ALSO
  36. L<BN_num_bytes(3)>, L<BN_add(3)>
  37. =head1 COPYRIGHT
  38. Copyright 2000-2017 The OpenSSL Project Authors. All Rights Reserved.
  39. Licensed under the Apache License 2.0 (the "License"). You may not use
  40. this file except in compliance with the License. You can obtain a copy
  41. in the file LICENSE in the source distribution or at
  42. L<https://www.openssl.org/source/license.html>.
  43. =cut