[vlc-devel] [PATCH v3 1/4] compat: add clock_gettime for darwin

[Rémi Denis-Courmont]

Le lauantaina 21. maaliskuuta 2020, 15.35.06 EET Marvin Scholz a écrit :
> ---
>  compat/clock_gettime.c | 127 +++++++++++++++++++++++++++++++++++++++++
>  configure.ac           |   2 +-
>  include/vlc_fixups.h   |  11 ++++
>  3 files changed, 139 insertions(+), 1 deletion(-)
>  create mode 100644 compat/clock_gettime.c
> 
> diff --git a/compat/clock_gettime.c b/compat/clock_gettime.c
> new file mode 100644
> index 0000000000..bcb0cc9df9
> --- /dev/null
> +++ b/compat/clock_gettime.c
> @@ -0,0 +1,127 @@
> +/**************************************************************************
> *** + * clock_gettime.c: POSIX clock_gettime() replacement
> +
> ***************************************************************************
> ** + * Copyright © 2020 VLC authors and VideoLAN
> + *
> + * Author: Marvin Scholz <epirat07 at gmail dot com>
> + *
> + * This program 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.
> + *
> + * This program 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 this program; if not, write to the Free Software Foundation,
> + * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA. +
> ***************************************************************************
> **/ +
> +#ifdef __APPLE__
> +
> +#ifdef HAVE_CONFIG_H
> +# include <config.h>
> +#endif
> +
> +#include <sys/errno.h>
> +#include <sys/types.h>
> +#include <sys/time.h>
> +#include <sys/sysctl.h>
> +
> +/**
> + * Get the absolute time at which the system was booted
> + *
> + * This time is changed whenever the clock is adjusted to
> + * correctly reflect the boot time with the adjusted clock,
> + * so just querying it once and reusing the value is not safe.
> + *
> + * \param[out]  tv   Timeval struct to write the boottime to
> + *
> + * \note
> + * The boot time only has microsecond precision
> + *
> + * \return 0 on success, else -1 and errno set
> + */
> +static int vlc__get_system_boottime(struct timeval *tv)
> +{
> +    int ret = sysctl((int[]){ CTL_KERN, KERN_BOOTTIME }, 2,
> +                     tv, &(size_t){ sizeof(*tv) }, NULL, 0);
> +
> +    if (ret != 0)
> +        return errno;
> +
> +    return 0;
> +}
> +
> +/**
> + * Get the monotonic time (CLOCK_MONOTONIC)
> + *
> + * Calculates a monotically incrasing time since system boot
> + * that continues to increment when the system is asleep.
> + *
> + * Warnings to everyone trying to simplify this:
> + * - Using mach_continuous_time is not equivalent to this, see
> + *   the darwin manpage about CLOCK_MONOTONIC_RAW for an explanation.
> + * - Using mach_absolute_time is not equivalent to this, as it does
> + *   not continue to increment when the system is asleep.
> + * - The boot time is queried twice in a loop and only used if both
> + *   match. This is done to detect if the boot time change since we
> + *   obtained the current time of day, as the boot time can change
> + *   when the system wallclock is adjusted, as that will adjust the
> + *   boot time accordingly.
> + *
> + * \param[out]  tv   Timeval struct to write the monotonic time to
> + *
> + * \return 0 on success, else -1 and errno set
> + */
> +static int vlc__get_monotonic(struct timeval *tv)
> +{
> +    int ret;
> +    struct timeval currenttime;
> +    struct timeval boottime_begin;
> +    struct timeval boottime_end;
> +
> +    do {
> +        ret = vlc__get_system_boottime(&boottime_begin);
> +        if (ret != 0)
> +            return ret;
> +
> +        ret = gettimeofday(&currenttime, NULL);
> +        if (ret != 0)
> +            return ret;
> +
> +        ret = vlc__get_system_boottime(&boottime_end);
> +        if (ret != 0)
> +            return ret;
> +    } while (timercmp(&boottime_begin, &boottime_end, !=));
> +
> +    timersub(&currenttime, &boottime_begin, tv);
> +    return 0;
> +}
> +
> +int clock_gettime(clockid_t clock_id, struct timespec *tp)
> +{
> +    int ret = 0;
> +    struct timeval tv;
> +
> +    switch (clock_id) {
> +        case CLOCK_MONOTONIC:
> +            ret = vlc__get_monotonic(&tv);
> +            break;
> +        case CLOCK_REALTIME:
> +            ret = gettimeofday(&tv, NULL);
> +            break;
> +        default:
> +            errno = EINVAL;
> +            return -1;
> +    }
> +
> +    if (ret == 0)
> +        TIMEVAL_TO_TIMESPEC(&tv, tp);
> +    return ret;
> +}
> +
> +#endif
> diff --git a/configure.ac b/configure.ac
> index bc1874cb97..4fd1a2058c 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -650,7 +650,7 @@ need_libc=false
>  dnl Check for usual libc functions
>  AC_CHECK_FUNCS([accept4 daemon fcntl flock fstatat fstatvfs fork
> getmntent_r getenv getpwuid_r isatty memalign mkostemp mmap open_memstream
> newlocale pipe2 pread posix_fadvise posix_madvise setlocale stricmp
> strnicmp strptime uselocale]) AC_REPLACE_FUNCS([aligned_alloc atof atoll
> dirfd fdopendir flockfile fsync getdelim getpid lfind lldiv memrchr nrand48
> poll posix_memalign recvmsg rewind sendmsg setenv strcasecmp strcasestr
> strdup strlcpy strndup strnlen strnstr strsep strtof strtok_r strtoll swab
> tdestroy tfind timegm timespec_get strverscmp pathconf])
> -AC_REPLACE_FUNCS([gettimeofday])
> +AC_REPLACE_FUNCS([gettimeofday clock_gettime])

You can't check this before -lrt.

>  AC_CHECK_FUNC(fdatasync,,
>    [AC_DEFINE(fdatasync, fsync, [Alias fdatasync() to fsync() if missing.])
>  ])
> diff --git a/include/vlc_fixups.h b/include/vlc_fixups.h
> index 8fd01da0ce..055bcf84d6 100644
> --- a/include/vlc_fixups.h
> +++ b/include/vlc_fixups.h
> @@ -658,6 +658,17 @@ FILE *vlc_win32_tmpfile(void);
> 
>  #ifdef __APPLE__
>  # define fdatasync fsync
> +
> +# include <time.h>
> +# ifndef CLOCK_REALTIME
> +#  define CLOCK_REALTIME 0
> +# endif
> +# ifndef CLOCK_MONOTONIC
> +#  define CLOCK_MONOTONIC 6
> +# endif
> +# ifndef HAVE_CLOCK_GETTIME
> +int clock_gettime(clockid_t clock_id, struct timespec *tp);
> +# endif
>  #endif
> 
>  #ifdef __cplusplus


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