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//
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//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
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// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#ifdef OS_WINDOWS
#include <windows.h>
#else
#include <pthread.h>
#endif
#ifdef OS_MACOSX
#include <libkern/OSAtomic.h>
#endif
#include "base/base.h"
#include "base/mutex.h"
namespace mozc {
// Wrapper for Windows InterlockedCompareExchange
namespace {
#ifdef OS_LINUX
// TODO(taku):
// Linux doesn't provide InterlockedCompareExchange-like function.
// we have to double-check it
inline int InterlockedCompareExchange(volatile int *target,
int new_value,
int old_value) {
#if defined(__GNUC__) && \
(__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 1)) && \
!defined(__arm__)
// Use GCC's extention (Note: ARM GCC doesn't have this function.)
// http://gcc.gnu.org/onlinedocs/gcc-4.1.2/gcc/Atomic-Builtins.html
return __sync_val_compare_and_swap(target, old_value, new_value);
#else
#ifdef __i486__
// Use cmpxchgl: http://0xcc.net/blog/archives/000128.html
int result;
asm volatile ("lock; cmpxchgl %1, %2"
: "=a" (result)
: "r" (new_value), "m" (*(target)), "0"(old_value)
: "memory", "cc");
return result;
#else // __i486__
// TODO(yusukes): Write a thread-safe implementation for ChromeOS for ARM.
// not thread safe
if (*target == old_value) {
*target = new_value;
return old_value;
}
return *target;
#endif // __i486__
#endif // __GNUC__
}
#endif // OS_LINUX
// Use OSAtomicCompareAndSwapInt on Mac OSX
// http://developer.apple.com/iphone/library/documentation/
// system/conceptual/manpages_iphoneos/man3/OSAtomicCompareAndSwapInt.3.html
// TODO(taku): should we use OSAtomicCompareAndSwapIntBarrier?
#ifdef OS_MACOSX
inline int InterlockedCompareExchange(volatile int *target,
int new_value,
int old_value) {
return OSAtomicCompareAndSwapInt(old_value, new_value, target)
? old_value : *target;
}
#endif // OX_MACOSX
} // namespace
void CallOnce(once_t *once, void (*func)()) {
if (once == NULL || func == NULL) {
return;
}
if (once->state != ONCE_INIT) {
return;
}
// change the counter in atomic
if (0 == InterlockedCompareExchange(&(once->counter), 1, 0)) {
// call func
(*func)();
// change the status to be ONCE_DONE in atomic
// Maybe we won't use it, but in order to make memory barrier,
// we use InterlockedCompareExchange just in case.
InterlockedCompareExchange(&(once->state), ONCE_DONE, ONCE_INIT);
} else {
while (once->state == ONCE_INIT) {
#ifdef OS_WINDOWS
YieldProcessor();
#endif
} // busy loop
}
}
void ResetOnce(once_t *once) {
InterlockedCompareExchange(&(once->state), ONCE_INIT, ONCE_DONE);
InterlockedCompareExchange(&(once->counter), 0, 1);
}
} // namespace mozc