printf throttle

#include 

#define NPRINT(n, ...) do { static int __t = 0; if (__t++ >= 0) printf(__VA_ARGS__),  __t = -(n)+1; } while(0)

int main() {
    for (int i = 0; i < 100; ++i)
    {
        NPRINT(10, "10 i = %d\n", i);
    }
    printf("--------\n");
    for (int i = 0; i < 100; ++i)
    {
        NPRINT(20, "20 i = %d\n", i);
    }

    return 0;
}

---

glog也有类似的宏，看一下大佬们是怎么写的

// Use macro expansion to create, for each use of LOG_EVERY_N(), static
// variables with the __LINE__ expansion as part of the variable name.
#define LOG_EVERY_N_VARNAME(base, line) LOG_EVERY_N_VARNAME_CONCAT(base, line)
#define LOG_EVERY_N_VARNAME_CONCAT(base, line) base ## line

#define LOG_OCCURRENCES LOG_EVERY_N_VARNAME(occurrences_, __LINE__)
#define LOG_OCCURRENCES_MOD_N LOG_EVERY_N_VARNAME(occurrences_mod_n_, __LINE__)

#define SOME_KIND_OF_LOG_EVERY_N(severity, n, what_to_do) \
  static int LOG_OCCURRENCES = 0, LOG_OCCURRENCES_MOD_N = 0; \
  ++LOG_OCCURRENCES; \
  if (++LOG_OCCURRENCES_MOD_N > n) LOG_OCCURRENCES_MOD_N -= n; \
  if (LOG_OCCURRENCES_MOD_N == 1) \
    google::LogMessage( \
        __FILE__, __LINE__, google::GLOG_ ## severity, LOG_OCCURRENCES, \
        &what_to_do).stream()

#define LOG_EVERY_N(severity, n)                                        \
  SOME_KIND_OF_LOG_EVERY_N(severity, (n), google::LogMessage::SendToLog)

用法

 LOG_EVERY_N(INFO, 3) << "LOG_EVERY_N 3 i:" << i << " google::COUNTER:" << google::COUNTER;

因为他用的c++的流式方法，所以不能像我这样用do while形式。
为了记录当前执行次数，用宏定义了一个 occurrences_LINE 的静态变量。宏玩的很溜啊。