Re: [PATCH 3/9] wrapper: add sleep_nanosec

[Junio C Hamano <gitster@pobox.com>]

Siddh Raman Pant <siddh.raman.pant@oracle.com> writes:

> Signed-off-by: Siddh Raman Pant <siddh.raman.pant@oracle.com>
> ---

The space above the signed-off-by line should be utilized to explain
why we want this change.  For the purpose of this series, why do we
want to sleep at nanosecond precision?

>  wrapper.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
>  wrapper.h |  1 +
>  2 files changed, 50 insertions(+)
>
> diff --git a/wrapper.c b/wrapper.c
> index 16f5a63fbb61..1349255f1eb4 100644
> --- a/wrapper.c
> +++ b/wrapper.c
> @@ -10,6 +10,7 @@
>  #include "gettext.h"
>  #include "strbuf.h"
>  #include "trace2.h"
> +#include <time.h>
>  
>  #ifdef HAVE_RTLGENRANDOM
>  /* This is required to get access to RtlGenRandom. */
> @@ -708,6 +709,54 @@ void sleep_millisec(int millisec)
>  	poll(NULL, 0, millisec);
>  }
>  
> +#ifdef GIT_WINDOWS_NATIVE
> +/* No nanosleep() on Windows, so fall-back to using sleep_millisec(). */
> +int sleep_nanosec(uint64_t nanosec)
> +{
> +	uint64_t ns_in_1ms = 1000000ULL;	/* 1 ms = 10^6 ns */
> +
> +	uint64_t millisec = nanosec / ns_in_1ms;
> +	if (nanosec % ns_in_1ms)
> +		millisec++;
> +
> +	/* Chunked sleep if we can't represent in integer. */
> +	while (millisec > INT_MAX) {
> +		sleep_millisec(INT_MAX);
> +		millisec -= INT_MAX;
> +	}
> +
> +	sleep_millisec((int)millisec);
> +
> +	return 0;
> +}
> +#else
> +/* Not Windows, so use the more exact nanosleep(). */
> +int sleep_nanosec(uint64_t nanosec)
> +{
> +	int ret;
> +	struct timespec duration, remaining;
> +
> +	/* Construct the duration by dividing the given total (1s = 10^9ns). */
> +	duration.tv_sec = nanosec / 1000000000ULL;
> +	duration.tv_nsec = nanosec % 1000000000ULL;
> +
> +	while(1) {
> +		ret = nanosleep(&duration, &remaining);
> +
> +		/* Continue sleeping if interrupted. */
> +		if (ret == -1 && errno == EINTR) {
> +			duration = remaining;
> +			continue;
> +		}
> +
> +		/* Either success or an error. */
> +		break;
> +	}
> +
> +	return ret;
> +}
> +#endif  /* GIT_WINDOWS_NATIVE */
> +
>  int xgethostname(char *buf, size_t len)
>  {
>  	/*
> diff --git a/wrapper.h b/wrapper.h
> index 15ac3bab6e97..c39992893a81 100644
> --- a/wrapper.h
> +++ b/wrapper.h
> @@ -130,6 +130,7 @@ int warn_on_fopen_errors(const char *path);
>  int open_nofollow(const char *path, int flags);
>  
>  void sleep_millisec(int millisec);
> +int sleep_nanosec(uint64_t nanosec);
>  
>  enum {
>  	/*