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Diffstat (limited to 'secure/lib/libcrypto/man/CRYPTO_THREAD_run_once.3')
| -rw-r--r-- | secure/lib/libcrypto/man/CRYPTO_THREAD_run_once.3 | 279 |
1 files changed, 279 insertions, 0 deletions
diff --git a/secure/lib/libcrypto/man/CRYPTO_THREAD_run_once.3 b/secure/lib/libcrypto/man/CRYPTO_THREAD_run_once.3 new file mode 100644 index 0000000000000..9d3700ed3ce0c --- /dev/null +++ b/secure/lib/libcrypto/man/CRYPTO_THREAD_run_once.3 @@ -0,0 +1,279 @@ +.\" Automatically generated by Pod::Man 4.09 (Pod::Simple 3.35) +.\" +.\" Standard preamble: +.\" ======================================================================== +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. \*(C+ will +.\" give a nicer C++. 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Always turn off hyphenation; it makes +.\" way too many mistakes in technical documents. +.if n .ad l +.nh +.SH "NAME" +CRYPTO_THREAD_run_once, CRYPTO_THREAD_lock_new, CRYPTO_THREAD_read_lock, CRYPTO_THREAD_write_lock, CRYPTO_THREAD_unlock, CRYPTO_THREAD_lock_free, CRYPTO_atomic_add \- OpenSSL thread support +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +.Vb 1 +\& #include <openssl/crypto.h> +\& +\& CRYPTO_ONCE CRYPTO_ONCE_STATIC_INIT; +\& int CRYPTO_THREAD_run_once(CRYPTO_ONCE *once, void (*init)(void)); +\& +\& CRYPTO_RWLOCK *CRYPTO_THREAD_lock_new(void); +\& int CRYPTO_THREAD_read_lock(CRYPTO_RWLOCK *lock); +\& int CRYPTO_THREAD_write_lock(CRYPTO_RWLOCK *lock); +\& int CRYPTO_THREAD_unlock(CRYPTO_RWLOCK *lock); +\& void CRYPTO_THREAD_lock_free(CRYPTO_RWLOCK *lock); +\& +\& int CRYPTO_atomic_add(int *val, int amount, int *ret, CRYPTO_RWLOCK *lock); +.Ve +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +OpenSSL can be safely used in multi-threaded applications provided that +support for the underlying \s-1OS\s0 threading \s-1API\s0 is built-in. Currently, OpenSSL +supports the pthread and Windows APIs. OpenSSL can also be built without +any multi-threading support, for example on platforms that don't provide +any threading support or that provide a threading \s-1API\s0 that is not yet +supported by OpenSSL. +.PP +The following multi-threading function are provided: +.IP "\(bu" 2 +\&\fICRYPTO_THREAD_run_once()\fR can be used to perform one-time initialization. +The \fBonce\fR argument must be a pointer to a static object of type +\&\fB\s-1CRYPTO_ONCE\s0\fR that was statically initialized to the value +\&\fB\s-1CRYPTO_ONCE_STATIC_INIT\s0\fR. +The \fBinit\fR argument is a pointer to a function that performs the desired +exactly once initialization. +In particular, this can be used to allocate locks in a thread-safe manner, +which can then be used with the locking functions below. +.IP "\(bu" 2 +\&\fICRYPTO_THREAD_lock_new()\fR allocates, initializes and returns a new read/write +lock. +.IP "\(bu" 2 +\&\fICRYPTO_THREAD_read_lock()\fR locks the provided \fBlock\fR for reading. +.IP "\(bu" 2 +\&\fICRYPTO_THREAD_write_lock()\fR locks the provided \fBlock\fR for writing. +.IP "\(bu" 2 +\&\fICRYPTO_THREAD_unlock()\fR unlocks the previously locked \fBlock\fR. +.IP "\(bu" 2 +\&\fICRYPTO_THREAD_lock_free()\fR frees the provided \fBlock\fR. +.IP "\(bu" 2 +\&\fICRYPTO_atomic_add()\fR atomically adds \fBamount\fR to \fBval\fR and returns the +result of the operation in \fBret\fR. \fBlock\fR will be locked, unless atomic +operations are supported on the specific platform. Because of this, if a +variable is modified by \fICRYPTO_atomic_add()\fR then \fICRYPTO_atomic_add()\fR must +be the only way that the variable is modified. +.SH "RETURN VALUES" +.IX Header "RETURN VALUES" +\&\fICRYPTO_THREAD_run_once()\fR returns 1 on success, or 0 on error. +.PP +\&\fICRYPTO_THREAD_lock_new()\fR returns the allocated lock, or \s-1NULL\s0 on error. +.PP +\&\fICRYPTO_THREAD_lock_free()\fR returns no value. +.PP +The other functions return 1 on success, or 0 on error. +.SH "NOTES" +.IX Header "NOTES" +On Windows platforms the CRYPTO_THREAD_* types and functions in the +openssl/crypto.h header are dependent on some of the types customarily +made available by including windows.h. The application developer is +likely to require control over when the latter is included, commonly as +one of the first included headers. Therefore it is defined as an +application developer's responsibility to include windows.h prior to +crypto.h where use of CRYPTO_THREAD_* types and functions is required. +.SH "EXAMPLE" +.IX Header "EXAMPLE" +This example safely initializes and uses a lock. +.PP +.Vb 4 +\& #ifdef _WIN32 +\& # include <windows.h> +\& #endif +\& #include <openssl/crypto.h> +\& +\& static CRYPTO_ONCE once = CRYPTO_ONCE_STATIC_INIT; +\& static CRYPTO_RWLOCK *lock; +\& +\& static void myinit(void) +\& { +\& lock = CRYPTO_THREAD_lock_new(); +\& } +\& +\& static int mylock(void) +\& { +\& if (!CRYPTO_THREAD_run_once(&once, void init) || lock == NULL) +\& return 0; +\& return CRYPTO_THREAD_write_lock(lock); +\& } +\& +\& static int myunlock(void) +\& { +\& return CRYPTO_THREAD_unlock(lock); +\& } +\& +\& int serialized(void) +\& { +\& int ret = 0; +\& +\& if (mylock()) { +\& /* Your code here, do not return without releasing the lock! */ +\& ret = ... ; +\& } +\& myunlock(); +\& return ret; +\& } +.Ve +.PP +Finalization of locks is an advanced topic, not covered in this example. +This can only be done at process exit or when a dynamically loaded library is +no longer in use and is unloaded. +The simplest solution is to just \*(L"leak\*(R" the lock in applications and not +repeatedly load/unload shared libraries that allocate locks. +.SH "NOTES" +.IX Header "NOTES" +You can find out if OpenSSL was configured with thread support: +.PP +.Vb 6 +\& #include <openssl/opensslconf.h> +\& #if defined(OPENSSL_THREADS) +\& /* thread support enabled */ +\& #else +\& /* no thread support */ +\& #endif +.Ve +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fIcrypto\fR\|(7) +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright 2000\-2018 The OpenSSL Project Authors. All Rights Reserved. +.PP +Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use +this file except in compliance with the License. You can obtain a copy +in the file \s-1LICENSE\s0 in the source distribution or at +<https://www.openssl.org/source/license.html>. |