openssl/doc/crypto/threads.pod
2000-02-24 01:20:31 +00:00

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=pod
=head1 NAME
CRYPTO_set_locking_callback, CRYPTO_set_id_callback - OpenSSL thread support
=head1 SYNOPSIS
#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);
=head1 DESCRIPTION
OpenSSL can safely be used in multi-threaded applications provided
that two callback functions are set.
locking_function(int mode, int type, const char *file, int line) is
needed to perform locking on shared data stuctures. 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 B<n>th lock if B<mode> &
B<CRYPTO_LOCK>, and releases it otherwise.
B<file> and B<line> are the file number of the function setting the
lock. They can be useful for debugging.
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.
=head1 RETURN VALUES
CRYPTO_num_locks() returns the required number of locks.
The other functions return no values.
=head1 NOTE
You can find out if OpenSSL was configured with thread support:
#define OPENSSL_THREAD_DEFINES
#include <openssl/opensslconf.h>
#if defined(THREADS)
// thread support enabled
#else
// no thread support
#endif
=head1 EXAMPLES
B<crypto/threads/mttest.c> shows examples of the callback functions on
Solaris, Irix and Win32.
=head1 HISTORY
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.
=head1 SEE ALSO
L<crypto(3)|crypto(3)>
=cut