+id_function(void) is a function that returns a numerical thread ID,
+for example pthread_self() if it returns an integer (see NOTES below).
+By OpenSSL's defaults, this is not needed on Windows nor on platforms
+where getpid() returns a different ID for each thread (see NOTES
+below).
+
+idptr_function(void) is a function that similarly returns a thread ID,
+but of type void *. This is not needed on platforms where &errno is
+different for each thread.
+
+Additionally, OpenSSL supports dynamic locks, and sometimes, some parts
+of OpenSSL need it for better performance. To enable this, the following
+is required:
+
+=over 4
+
+=item *
+Three additional callback function, dyn_create_function, dyn_lock_function
+and dyn_destroy_function.
+
+=item *
+A structure defined with the data that each lock needs to handle.
+
+=back
+
+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