BN_set_bit.pod 1.9 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)|ERR_get_error(3)>.
  35. =head1 SEE ALSO
  36. L<bn(3)|bn(3)>, L<BN_num_bytes(3)|BN_num_bytes(3)>, L<BN_add(3)|BN_add(3)>
  37. =head1 HISTORY
  38. BN_set_bit(), BN_clear_bit(), BN_is_bit_set(), BN_mask_bits(),
  39. BN_lshift(), BN_lshift1(), BN_rshift(), and BN_rshift1() are available
  40. in all versions of SSLeay and OpenSSL.
  41. =cut