From 65f1d45dcc71186ede72fff950996099d23359bd Mon Sep 17 00:00:00 2001 From: "Ronald S. Bultje" Date: Sun, 2 Dec 2012 14:34:50 -0800 Subject: lavu: add support for atomic operations. These could be used for reference counting, or for keeping track of decoding progress in references in multithreaded decoders. Support is provided by gcc/msvc/suncc intrinsics, with a fallback using pthread mutexes. Signed-off-by: Anton Khirnov --- libavutil/atomic.c | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) create mode 100644 libavutil/atomic.c (limited to 'libavutil/atomic.c') diff --git a/libavutil/atomic.c b/libavutil/atomic.c new file mode 100644 index 0000000000..8fa2532fd6 --- /dev/null +++ b/libavutil/atomic.c @@ -0,0 +1,123 @@ +/* + * Copyright (c) 2012 Ronald S. Bultje + * + * This file is part of Libav. + * + * Libav is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * Libav is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with Libav; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include "atomic.h" + +#if !HAVE_MEMORYBARRIER && !HAVE_SYNC_SYNCHRONIZE && !HAVE_MACHINE_RW_BARRIER + +#if HAVE_PTHREADS + +#include + +static pthread_mutex_t atomic_lock = PTHREAD_MUTEX_INITIALIZER; + +int avpriv_atomic_int_get(volatile int *ptr) +{ + int res; + + pthread_mutex_lock(&atomic_lock); + res = *ptr; + pthread_mutex_unlock(&atomic_lock); + + return res; +} + +void avpriv_atomic_int_set(volatile int *ptr, int val) +{ + pthread_mutex_lock(&atomic_lock); + *ptr = val; + pthread_mutex_unlock(&atomic_lock); +} + +int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc) +{ + int res; + + pthread_mutex_lock(&atomic_lock); + *ptr += inc; + res = *ptr; + pthread_mutex_unlock(&atomic_lock); + + return res; +} + +void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval) +{ + void *ret; + pthread_mutex_lock(&atomic_lock); + ret = *ptr; + if (*ptr == oldval) + *ptr = newval; + pthread_mutex_unlock(&atomic_lock); + return ret; +} + +#elif !HAVE_THREADS + +int avpriv_atomic_int_get(volatile int *ptr) +{ + return *ptr; +} + +void avpriv_atomic_int_set(volatile int *ptr, int val) +{ + *ptr = val; +} + +int avpriv_atomic_int_add_and_fetch(volatile int *ptr, int inc) +{ + *ptr += inc; + return *ptr; +} + +void *avpriv_atomic_ptr_cas(void * volatile *ptr, void *oldval, void *newval) +{ + if (*ptr == oldval) { + *ptr = newval; + return oldval; + } + return *ptr; +} + +#else + +#error "Threading is enabled, but there is no implementation of atomic operations available" + +#endif /* HAVE_PTHREADS */ + +#endif /* !HAVE_MEMORYBARRIER && !HAVE_SYNC_SYNCHRONIZE && !HAVE_MACHINE_RW_BARRIER */ + +#ifdef TEST +#include + +int main(void) +{ + volatile int val = 1; + int res; + + res = avpriv_atomic_int_add_and_fetch(&val, 1); + assert(res == 2); + avpriv_atomic_int_set(&val, 3); + res = avpriv_atomic_int_get(&val); + assert(res == 3); + + return 0; +} +#endif -- cgit v1.2.3