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threads(3)				     OpenSSL				       threads(3)

       CRYPTO_set_locking_callback, CRYPTO_set_id_callback, CRYPTO_num_locks, CRYPTO_set_dyn-
       lock_create_callback, CRYPTO_set_dynlock_lock_callback, CRYPTO_set_dynlock_destroy_call-
       back, CRYPTO_get_new_dynlockid, CRYPTO_destroy_dynlockid, CRYPTO_lock - OpenSSL thread

	#include <openssl/crypto.h>

	void CRYPTO_set_locking_callback(void (*locking_function)(int mode,
	       int n, const char *file, int line));

	void CRYPTO_set_id_callback(unsigned long (*id_function)(void));

	int CRYPTO_num_locks(void);

	/* struct CRYPTO_dynlock_value needs to be defined by the user */
	struct CRYPTO_dynlock_value;

	void CRYPTO_set_dynlock_create_callback(struct CRYPTO_dynlock_value *
	       (*dyn_create_function)(char *file, int line));
	void CRYPTO_set_dynlock_lock_callback(void (*dyn_lock_function)
	       (int mode, struct CRYPTO_dynlock_value *l,
	       const char *file, int line));
	void CRYPTO_set_dynlock_destroy_callback(void (*dyn_destroy_function)
	       (struct CRYPTO_dynlock_value *l, const char *file, int line));

	int CRYPTO_get_new_dynlockid(void);

	void CRYPTO_destroy_dynlockid(int i);

	void CRYPTO_lock(int mode, int n, const char *file, int line);

	#define CRYPTO_w_lock(type)    \
	#define CRYPTO_w_unlock(type)  \
	#define CRYPTO_r_lock(type)    \
	#define CRYPTO_r_unlock(type)  \
	#define CRYPTO_add(addr,amount,type)   \

       OpenSSL can safely be used in multi-threaded applications provided that at least two call-
       back functions are set.

       locking_function(int mode, int n, const char *file, int line) is needed to perform locking
       on shared data structures.  (Note that OpenSSL uses a number of global data structures
       that will be implicitly shared whenever multiple threads use OpenSSL.)  Multi-threaded
       applications will crash at random if it is not set.

       locking_function() must be able to handle up to CRYPTO_num_locks() different mutex locks.
       It sets the n-th lock if mode & CRYPTO_LOCK, and releases it otherwise.

       file and line are the file number of the function setting the lock. They can be useful for

       id_function(void) is a function that returns a thread ID. It is not needed on Windows nor
       on platforms where getpid() returns a different ID for each thread (most notably Linux).

       Additionally, OpenSSL supports dynamic locks, and sometimes, some parts of OpenSSL need it
       for better performance.	To enable this, the following is required:

       * Three additional callback function, dyn_create_function, dyn_lock_function and
       * A structure defined with the data that each lock needs to handle.

       struct CRYPTO_dynlock_value has to be defined to contain whatever structure is needed to
       handle locks.

       dyn_create_function(const char *file, int line) is needed to create a lock.  Multi-
       threaded applications might crash at random if it is not set.

       dyn_lock_function(int mode, CRYPTO_dynlock *l, const char *file, int line) is needed to
       perform locking off dynamic lock numbered n. Multi-threaded applications might crash at
       random if it is not set.

       dyn_destroy_function(CRYPTO_dynlock *l, const char *file, int line) is needed to destroy
       the lock l. Multi-threaded applications might crash at random if it is not set.

       CRYPTO_get_new_dynlockid() is used to create locks.  It will call dyn_create_function for
       the actual creation.

       CRYPTO_destroy_dynlockid() is used to destroy locks.  It will call dyn_destroy_function
       for the actual destruction.

       CRYPTO_lock() is used to lock and unlock the locks.  mode is a bitfield describing what
       should be done with the lock.  n is the number of the lock as returned from
       CRYPTO_get_new_dynlockid().  mode can be combined from the following values.  These values
       are pairwise exclusive, with undefined behaviour if misused (for example, CRYPTO_READ and
       CRYPTO_WRITE should not be used together):

	       CRYPTO_LOCK     0x01
	       CRYPTO_UNLOCK   0x02
	       CRYPTO_READ     0x04
	       CRYPTO_WRITE    0x08

       CRYPTO_num_locks() returns the required number of locks.

       CRYPTO_get_new_dynlockid() returns the index to the newly created lock.

       The other functions return no values.

       You can find out if OpenSSL was configured with thread support:

	#include <openssl/opensslconf.h>
	#if defined(THREADS)
	  // thread support enabled
	  // no thread support

       Also, dynamic locks are currently not used internally by OpenSSL, but may do so in the

       crypto/threads/mttest.c shows examples of the callback functions on Solaris, Irix and

       CRYPTO_set_locking_callback() and CRYPTO_set_id_callback() are available in all versions
       of SSLeay and OpenSSL.  CRYPTO_num_locks() was added in OpenSSL 0.9.4.  All functions
       dealing with dynamic locks were added in OpenSSL 0.9.5b-dev.


0.9.7d					    2003-11-20				       threads(3)
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