Enji Cooper
115 lines
3.5 KiB
Plaintext
115 lines
3.5 KiB
Plaintext
.\" -*- mode: troff; coding: utf-8 -*-
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.\" Automatically generated by Pod::Man v6.0.2 (Pod::Simple 3.45)
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.\" ========================================================================
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.\"
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.IX Title "BN_CTX_START 3ossl"
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.TH BN_CTX_START 3ossl 2026-01-27 3.5.5 OpenSSL
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.\" For nroff, turn off justification. Always turn off hyphenation; it makes
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.\" way too many mistakes in technical documents.
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.nh
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.SH NAME
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BN_CTX_start, BN_CTX_get, BN_CTX_end \- use temporary BIGNUM variables
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.SH SYNOPSIS
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.IX Header "SYNOPSIS"
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.Vb 1
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\& #include <openssl/bn.h>
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\&
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\& void BN_CTX_start(BN_CTX *ctx);
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\&
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\& BIGNUM *BN_CTX_get(BN_CTX *ctx);
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\&
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\& void BN_CTX_end(BN_CTX *ctx);
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.Ve
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.SH DESCRIPTION
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.IX Header "DESCRIPTION"
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These functions are used to obtain temporary \fBBIGNUM\fR variables from
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a \fBBN_CTX\fR (which can been created by using \fBBN_CTX_new\fR\|(3))
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in order to save the overhead of repeatedly creating and
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freeing \fBBIGNUM\fRs in functions that are called from inside a loop.
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.PP
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A function must call \fBBN_CTX_start()\fR first. Then, \fBBN_CTX_get()\fR may be
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called repeatedly to obtain temporary \fBBIGNUM\fRs. All \fBBN_CTX_get()\fR
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calls must be made before calling any other functions that use the
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\&\fBctx\fR as an argument.
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.PP
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Finally, \fBBN_CTX_end()\fR must be called before returning from the function.
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If \fBctx\fR is NULL, nothing is done.
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When \fBBN_CTX_end()\fR is called, the \fBBIGNUM\fR pointers obtained from
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\&\fBBN_CTX_get()\fR become invalid.
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.SH "RETURN VALUES"
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.IX Header "RETURN VALUES"
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\&\fBBN_CTX_start()\fR and \fBBN_CTX_end()\fR return no values.
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.PP
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\&\fBBN_CTX_get()\fR returns a pointer to the \fBBIGNUM\fR, or \fBNULL\fR on error.
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Once \fBBN_CTX_get()\fR has failed, the subsequent calls will return \fBNULL\fR
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as well, so it is sufficient to check the return value of the last
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\&\fBBN_CTX_get()\fR call. In case of an error, an error code is set, which
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can be obtained by \fBERR_get_error\fR\|(3).
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.SH "SEE ALSO"
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.IX Header "SEE ALSO"
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\&\fBBN_CTX_new\fR\|(3)
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.SH COPYRIGHT
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.IX Header "COPYRIGHT"
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Copyright 2000\-2016 The OpenSSL Project Authors. All Rights Reserved.
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.PP
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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<https://www.openssl.org/source/license.html>.
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