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Editing: BN_mask_bits.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "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 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #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); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" \&\fBBN_set_bit()\fR sets bit \fBn\fR in \fBa\fR to 1 (\f(CW\*(C`a|=(1<<n)\*(C'\fR). The number is expanded if necessary. .PP \&\fBBN_clear_bit()\fR sets bit \fBn\fR in \fBa\fR to 0 (\f(CW\*(C`a&=~(1<<n)\*(C'\fR). An error occurs if \fBa\fR is shorter than \fBn\fR bits. .PP \&\fBBN_is_bit_set()\fR tests if bit \fBn\fR in \fBa\fR is set. .PP \&\fBBN_mask_bits()\fR truncates \fBa\fR to an \fBn\fR bit number (\f(CW\*(C`a&=~((~0)>>n)\*(C'\fR). An error occurs if \fBa\fR already is shorter than \fBn\fR bits. .PP \&\fBBN_lshift()\fR shifts \fBa\fR left by \fBn\fR bits and places the result in \&\fBr\fR (\f(CW\*(C`r=a*2^n\*(C'\fR). Note that \fBn\fR must be non-negative. \fBBN_lshift1()\fR shifts \&\fBa\fR left by one and places the result in \fBr\fR (\f(CW\*(C`r=2*a\*(C'\fR). .PP \&\fBBN_rshift()\fR shifts \fBa\fR right by \fBn\fR bits and places the result in \&\fBr\fR (\f(CW\*(C`r=a/2^n\*(C'\fR). Note that \fBn\fR must be non-negative. \fBBN_rshift1()\fR shifts \&\fBa\fR right by one and places the result in \fBr\fR (\f(CW\*(C`r=a/2\*(C'\fR). .PP For the shift functions, \fBr\fR and \fBa\fR may be the same variable. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBBN_is_bit_set()\fR returns 1 if the bit is set, 0 otherwise. .PP All other functions return 1 for success, 0 on error. The error codes can be obtained by \fBERR_get_error\fR\|(3). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBbn\fR\|(3), \fBBN_num_bytes\fR\|(3), \fBBN_add\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" \&\fBBN_set_bit()\fR, \fBBN_clear_bit()\fR, \fBBN_is_bit_set()\fR, \fBBN_mask_bits()\fR, \&\fBBN_lshift()\fR, \fBBN_lshift1()\fR, \fBBN_rshift()\fR, and \fBBN_rshift1()\fR are available in all versions of SSLeay and OpenSSL.
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