threads(3) OpenSSL threads(3)

NAME
       CRYPTOsetlockingcallback, CRYPTOsetidcallback, CRYPTOnumlocks,
       CRYPTOsetdynlockcreatecallback, CRYPTOsetdynlocklockcallback,
       CRYPTOsetdynlockdestroycallback, CRYPTOgetnewdynlockid,
       CRYPTOdestroydynlockid, CRYPTOlock - OpenSSL thread support

SYNOPSIS
        #include 

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

        void CRYPTOsetidcallback(unsigned long (*idfunction)(void));

        int CRYPTOnumlocks(void);


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

        void CRYPTOsetdynlockcreatecallback(struct CRYPTOdynlockvalue *
               (*dyncreatefunction)(char *file, int line));
        void CRYPTOsetdynlocklockcallback(void (*dynlockfunction)
               (int mode, struct CRYPTOdynlockvalue *l,
               const char *file, int line));
        void CRYPTOsetdynlockdestroycallback(void (*dyndestroyfunction)
               (struct CRYPTOdynlockvalue *l, const char *file, int line));

        int CRYPTOgetnewdynlockid(void);

        void CRYPTOdestroydynlockid(int i);

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

        #define CRYPTOwlock(type)    \
               CRYPTOlock(CRYPTOLOCK|CRYPTOWRITE,type,FILE,LINE)
        #define CRYPTOwunlock(type)  \
               CRYPTOlock(CRYPTOUNLOCK|CRYPTOWRITE,type,FILE,LINE)
        #define CRYPTOrlock(type)    \
               CRYPTOlock(CRYPTOLOCK|CRYPTOREAD,type,FILE,LINE)
        #define CRYPTOrunlock(type)  \
               CRYPTOlock(CRYPTOUNLOCK|CRYPTOREAD,type,FILE,LINE)
        #define CRYPTOadd(addr,amount,type)   \
               CRYPTOaddlock(addr,amount,type,FILE,LINE)

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

       lockingfunction(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.

       lockingfunction() must be able to handle up to CRYPTOnumlocks()
       different mutex locks. It sets the nn-th lock if mmooddee & CCRRYYPPTTOOLLOOCCKK, and
       releases it otherwise.

       ffiillee and lliinnee are the file number of the function setting the lock.
       They can be useful for debugging.

       idfunction(void) is a function that returns a thread ID, for example
       pthreadself() if it returns an integer (see NOTES below).  It isn't
       needed on Windows nor on platforms where getpid() returns a different
       ID for each thread (see NOTES below).

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

       +o   Three additional callback function, dyncreatefunction,
           dynlockfunction and dyndestroyfunction.

       +o   A structure defined with the data that each lock needs to handle.

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

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

       dynlockfunction(int mode, CRYPTOdynlock *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.

       dyndestroyfunction(CRYPTOdynlock *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.

       CRYPTOgetnewdynlockid() is used to create locks.  It will call
       dyncreatefunction for the actual creation.

       CRYPTOdestroydynlockid() is used to destroy locks.  It will call
       dyndestroyfunction for the actual destruction.

       CRYPTOlock() 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 CRYPTOgetnewdynlockid().  mode can be combined
       from the following values.  These values are pairwise exclusive, with
       undefined behaviour if misused (for example, CRYPTOREAD and
       CRYPTOWRITE should not be used together):

               CRYPTOLOCK     0x01
               CRYPTOUNLOCK   0x02
               CRYPTOREAD     0x04
               CRYPTOWRITE    0x08

RETURN VALUES
       CRYPTOnumlocks() returns the required number of locks.

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

       The other functions return no values.

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

        #define OPENSSLTHREADDEFINES
        #include 
        #if defined(OPENSSLTHREADS)
          // thread support enabled
        #else
          // no thread support
        #endif

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

       Defining idfunction(void) has it's own issues.  Generally speaking,
       pthreadself() should be used, even on platforms where getpid() gives
       different answers in each thread, since that may depend on the machine
       the program is run on, not the machine where the program is being
       compiled.  For instance, Red Hat 8 Linux and earlier used LinuxThreads,
       whose getpid() returns a different value for each thread.  Red Hat 9
       Linux and later use NPTL, which is Posix-conformant, and has a getpid()
       that returns the same value for all threads in a process.  A program
       compiled on Red Hat 8 and run on Red Hat 9 will therefore see getpid()
       returning the same value for all threads.

       There is still the issue of platforms where pthreadself() returns
       something other than an integer.  This is a bit unusual, and this
       manual has no cookbook solution for that case.

EEXXAAMMPPLLEESS
       ccrryyppttoo//tthhrreeaaddss//mmtttteesstt..cc shows examples of the callback functions on
       Solaris, Irix and Win32.

HISTORY       CRYPTOsetlockingcallback() and CRYPTOsetidcallback() are
       available in all versions of SSLeay and OpenSSL.  CRYPTOnumlocks()
       was added in OpenSSL 0.9.4.  All functions dealing with dynamic locks
       were added in OpenSSL 0.9.5b-dev.

SEE ALSO
       crypto(3)



0.9.7l                            2005-06-17                        threads(3)