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52 lines
1.4 KiB
52 lines
1.4 KiB
=pod
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=head1 NAME
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BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
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=head1 SYNOPSIS
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#include <openssl/bn.h>
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void BN_CTX_start(BN_CTX *ctx);
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BIGNUM *BN_CTX_get(BN_CTX *ctx);
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void BN_CTX_end(BN_CTX *ctx);
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=head1 DESCRIPTION
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These functions are used to obtain temporary B<BIGNUM> variables from
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a B<BN_CTX> (which can been created by using L<BN_CTX_new(3)|BN_CTX_new(3)>)
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in order to save the overhead of repeatedly creating and
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freeing B<BIGNUM>s in functions that are called from inside a loop.
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A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
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called repeatedly to obtain temporary B<BIGNUM>s. All BN_CTX_get()
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calls must be made before calling any other functions that use the
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B<ctx> as an argument.
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Finally, BN_CTX_end() must be called before returning from the function.
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When BN_CTX_end() is called, the B<BIGNUM> pointers obtained from
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BN_CTX_get() become invalid.
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=head1 RETURN VALUES
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BN_CTX_start() and BN_CTX_end() return no values.
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BN_CTX_get() returns a pointer to the B<BIGNUM>, or B<NULL> on error.
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Once BN_CTX_get() has failed, the subsequent calls will return B<NULL>
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as well, so it is sufficient to check the return value of the last
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BN_CTX_get() call. In case of an error, an error code is set, which
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can be obtained by L<ERR_get_error(3)|ERR_get_error(3)>.
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=head1 SEE ALSO
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L<BN_CTX_new(3)|BN_CTX_new(3)>
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=head1 HISTORY
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BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL 0.9.5.
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=cut
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