BN_copy.3ossl 6.2 KB

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  133. .\" ========================================================================
  134. .\"
  135. .IX Title "BN_COPY 3ossl"
  136. .TH BN_COPY 3ossl "2024-09-03" "3.3.2" "OpenSSL"
  137. .\" For nroff, turn off justification. Always turn off hyphenation; it makes
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  139. .if n .ad l
  140. .nh
  141. .SH "NAME"
  142. BN_copy, BN_dup, BN_with_flags \- copy BIGNUMs
  143. .SH "SYNOPSIS"
  144. .IX Header "SYNOPSIS"
  145. .Vb 1
  146. \& #include <openssl/bn.h>
  147. \&
  148. \& BIGNUM *BN_copy(BIGNUM *to, const BIGNUM *from);
  149. \&
  150. \& BIGNUM *BN_dup(const BIGNUM *from);
  151. \&
  152. \& void BN_with_flags(BIGNUM *dest, const BIGNUM *b, int flags);
  153. .Ve
  154. .SH "DESCRIPTION"
  155. .IX Header "DESCRIPTION"
  156. \&\fBBN_copy()\fR copies \fBfrom\fR to \fBto\fR. \fBBN_dup()\fR creates a new \fB\s-1BIGNUM\s0\fR
  157. containing the value \fBfrom\fR.
  158. .PP
  159. BN_with_flags creates a \fBtemporary\fR shallow copy of \fBb\fR in \fBdest\fR. It places
  160. significant restrictions on the copied data. Applications that do no adhere to
  161. these restrictions may encounter unexpected side effects or crashes. For that
  162. reason use of this function is discouraged. Any flags provided in \fBflags\fR will
  163. be set in \fBdest\fR in addition to any flags already set in \fBb\fR. For example this
  164. might commonly be used to create a temporary copy of a \s-1BIGNUM\s0 with the
  165. \&\fB\s-1BN_FLG_CONSTTIME\s0\fR flag set for constant time operations. The temporary copy in
  166. \&\fBdest\fR will share some internal state with \fBb\fR. For this reason the following
  167. restrictions apply to the use of \fBdest\fR:
  168. .IP "\(bu" 2
  169. \&\fBdest\fR should be a newly allocated \s-1BIGNUM\s0 obtained via a call to \fBBN_new()\fR. It
  170. should not have been used for other purposes or initialised in any way.
  171. .IP "\(bu" 2
  172. \&\fBdest\fR must only be used in \*(L"read-only\*(R" operations, i.e. typically those
  173. functions where the relevant parameter is declared \*(L"const\*(R".
  174. .IP "\(bu" 2
  175. \&\fBdest\fR must be used and freed before any further subsequent use of \fBb\fR
  176. .SH "RETURN VALUES"
  177. .IX Header "RETURN VALUES"
  178. \&\fBBN_copy()\fR returns \fBto\fR on success, \s-1NULL\s0 on error. \fBBN_dup()\fR returns
  179. the new \fB\s-1BIGNUM\s0\fR, and \s-1NULL\s0 on error. The error codes can be obtained
  180. by \fBERR_get_error\fR\|(3).
  181. .SH "SEE ALSO"
  182. .IX Header "SEE ALSO"
  183. \&\fBERR_get_error\fR\|(3)
  184. .SH "COPYRIGHT"
  185. .IX Header "COPYRIGHT"
  186. Copyright 2000\-2017 The OpenSSL Project Authors. All Rights Reserved.
  187. .PP
  188. Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use
  189. this file except in compliance with the License. You can obtain a copy
  190. in the file \s-1LICENSE\s0 in the source distribution or at
  191. <https://www.openssl.org/source/license.html>.