1BN_CTX_start(3)                     OpenSSL                    BN_CTX_start(3)
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NAME

6       BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
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SYNOPSIS

9        #include <openssl/bn.h>
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11        void BN_CTX_start(BN_CTX *ctx);
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13        BIGNUM *BN_CTX_get(BN_CTX *ctx);
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15        void BN_CTX_end(BN_CTX *ctx);
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DESCRIPTION

18       These functions are used to obtain temporary BIGNUM variables from a
19       BN_CTX (which can been created by using BN_CTX_new(3)) in order to save
20       the overhead of repeatedly creating and freeing BIGNUMs in functions
21       that are called from inside a loop.
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23       A function must call BN_CTX_start() first. Then, BN_CTX_get() may be
24       called repeatedly to obtain temporary BIGNUMs. All BN_CTX_get() calls
25       must be made before calling any other functions that use the ctx as an
26       argument.
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28       Finally, BN_CTX_end() must be called before returning from the
29       function.  When BN_CTX_end() is called, the BIGNUM pointers obtained
30       from BN_CTX_get() become invalid.
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RETURN VALUES

33       BN_CTX_start() and BN_CTX_end() return no values.
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35       BN_CTX_get() returns a pointer to the BIGNUM, or NULL on error.  Once
36       BN_CTX_get() has failed, the subsequent calls will return NULL as well,
37       so it is sufficient to check the return value of the last BN_CTX_get()
38       call. In case of an error, an error code is set, which can be obtained
39       by ERR_get_error(3).
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SEE ALSO

42       BN_CTX_new(3)
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HISTORY

45       BN_CTX_start(), BN_CTX_get() and BN_CTX_end() were added in OpenSSL
46       0.9.5.
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501.0.2o                            2019-09-10                   BN_CTX_start(3)