Some Notes

最新推荐文章于 2025-08-12 10:45:10 发布

原创最新推荐文章于 2025-08-12 10:45:10 发布 · 668 阅读

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#struct #xcode #macros #library #function #image

1. LinuxThreads Frequently Asked Questions

http://cristal.inria.fr/~xleroy/linuxthreads/faq.html#F

Q: Where is pthread_yield()?

Because it's not part of the (final) POSIX 1003.1c standard. Several drafts of the standard contained pthread_yield(), but then the POSIX guys discovered it was redundant withsched_yield() and dropped it. So, just use sched_yield() instead.

2. Mac OX 下没有实现clock_gettime()。参考下面的连接

Monotonic time in Mac OS X

http://www.wand.net.nz/~smr26/wordpress/2009/01/19/monotonic-time-in-mac-os-x/

pthread_cond_timedwait 要用到struct timespec ，可以如下转换：

 struct timespec   ts;
  struct timeval    tv;
  int rc =  gettimeofday(&tp, NULL);

    /* Convert from timeval to timespec */
    ts.tv_sec  = tv.tv_sec;
    ts.tv_nsec = tv.tv_usec * 1000;
    ts.tv_sec += WAIT_TIME_SECONDS;

3. Making movies from image files using ffmpeg/mencoder

http://electron.mit.edu/~gsteele/ffmpeg/

ffmpeg -r 10 -b 2048k -i %05d.jpg test1800.mp4

mencoder "mf://*.jpg" -mf fps=10 -o test.avi -ovc lavc -lavcopts vcodec=msmpeg4v2:vbitrate=800 

4. 关于isnan()

http://stackoverflow.com/questions/570669/checking-if-a-double-or-float-is-nan-in-c

There is no isnan() function available in current C++ Standard Library. It was introduced in C99 and defined as a macro not a function. Elements of standard library defined by C99 are not part of current C++ standard ISO/IEC 14882:1998 neither its update ISO/IEC 14882:2003.

If TR1 is available, then cmath includes C99 elements like isnan(), isfinite(), etc. but they are defined as functions, not macros, usually in std::tr1:: namespace, though many implementations (i.e. GCC 4+ on Linux or in XCode on Mac OS X 10.5+) inject them directly to std::, so std::isnanis well defined.

所以很简单：using namespace std;