1BN_CTX_start(3) OpenSSL BN_CTX_start(3)
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6 BN_CTX_start, BN_CTX_get, BN_CTX_end - use temporary BIGNUM variables
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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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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
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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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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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42 BN_CTX_new(3)
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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 2020-08-01 BN_CTX_start(3)