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Editing: BN_CTX_start.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_CTX_start, BN_CTX_get, BN_CTX_end \- use temporary BIGNUM variables .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include <openssl/bn.h> \& \& void BN_CTX_start(BN_CTX *ctx); \& \& BIGNUM *BN_CTX_get(BN_CTX *ctx); \& \& void BN_CTX_end(BN_CTX *ctx); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" These functions are used to obtain temporary \fB\s-1BIGNUM\s0\fR variables from a \fB\s-1BN_CTX\s0\fR (which can been created by using \fBBN_CTX_new\fR\|(3)) in order to save the overhead of repeatedly creating and freeing \fB\s-1BIGNUM\s0\fRs in functions that are called from inside a loop. .PP A function must call \fBBN_CTX_start()\fR first. Then, \fBBN_CTX_get()\fR may be called repeatedly to obtain temporary \fB\s-1BIGNUM\s0\fRs. All \fBBN_CTX_get()\fR calls must be made before calling any other functions that use the \&\fBctx\fR as an argument. .PP Finally, \fBBN_CTX_end()\fR must be called before returning from the function. When \fBBN_CTX_end()\fR is called, the \fB\s-1BIGNUM\s0\fR pointers obtained from \&\fBBN_CTX_get()\fR become invalid. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBBN_CTX_start()\fR and \fBBN_CTX_end()\fR return no values. .PP \&\fBBN_CTX_get()\fR returns a pointer to the \fB\s-1BIGNUM\s0\fR, or \fB\s-1NULL\s0\fR on error. Once \fBBN_CTX_get()\fR has failed, the subsequent calls will return \fB\s-1NULL\s0\fR as well, so it is sufficient to check the return value of the last \&\fBBN_CTX_get()\fR call. In case of an error, an error code is set, which can be obtained by \fBERR_get_error\fR\|(3). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBBN_CTX_new\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" \&\fBBN_CTX_start()\fR, \fBBN_CTX_get()\fR and \fBBN_CTX_end()\fR were added in OpenSSL 0.9.5.
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