[vlc-devel] [PATCH 2/3] compat: add clock_nanosleep for darwin

[Rémi Denis-Courmont]

Le tiistaina 10. maaliskuuta 2020, 11.50.07 EET Marvin Scholz a écrit :
> ---
>  compat/clock_nanosleep.c | 109 +++++++++++++++++++++++++++++++++++++++
>  configure.ac             |   4 +-
>  include/vlc_fixups.h     |   7 +++
>  3 files changed, 119 insertions(+), 1 deletion(-)
>  create mode 100644 compat/clock_nanosleep.c
> 
> diff --git a/compat/clock_nanosleep.c b/compat/clock_nanosleep.c
> new file mode 100644
> index 0000000000..374e4668e2
> --- /dev/null
> +++ b/compat/clock_nanosleep.c
> @@ -0,0 +1,109 @@
> +/**************************************************************************
> *** + * clock_nanosleep.c: POSIX clock_nanosleep() 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. +
> ***************************************************************************
> **/ +
> +#ifndef __APPLE__
> +# error clock_nanosleep not implemented on your platform!
> +#endif

Same as 1/3

> +
> +#ifdef HAVE_CONFIG_H
> +# include <config.h>
> +#endif
> +
> +#define _DARWIN_C_SOURCE
> +#define _POSIX_C_SOURCE  200809L
> +
> +#include <assert.h>
> +#include <pthread.h>
> +#include <sys/errno.h>
> +#include <sys/types.h>
> +#include <sys/time.h>
> +#include <sys/sysctl.h>
> +#include <mach/clock_types.h>
> +
> +#define timespecs_sub(tsa, tsb, tsr)                                \
> +    do {                                                            \
> +            (tsr)->tv_sec = (tsa)->tv_sec - (tsb)->tv_sec;          \
> +            (tsr)->tv_nsec = (tsa)->tv_nsec - (tsb)->tv_nsec;       \
> +            if ((tsr)->tv_nsec < 0) {                               \
> +                    (tsr)->tv_sec--;                                \
> +                    (tsr)->tv_nsec += NSEC_PER_SEC;                 \
> +            }                                                       \
> +    } while (0)
> +
> +#define timespec_zero(ts) \
> +    ((ts)->tv_sec == 0 && (ts)->tv_nsec == 0)
> +
> +int clock_nanosleep(clockid_t clock_id, int flags,
> +        const struct timespec *rqtp, struct timespec *rmtp)
> +{
> +    struct timespec ts_rel;
> +
> +    // Validate timespec
> +    if (rqtp == NULL || rqtp->tv_sec < 0 ||
> +            rqtp->tv_nsec < 0 || (unsigned long)rqtp->tv_nsec >=
> NSEC_PER_SEC) { +        errno = EINVAL;
> +        return -1;
> +    }
> +
> +    if (flags == TIMER_ABSTIME) {
> +        struct timespec ts_now;
> +
> +        // We don't support waiting for a absolute wallclock time currently
> +        if (clock_id == CLOCK_REALTIME) {
> +            assert(!!"Absolute wait for wallclock not implemented on
> Darwin!");

Should probably be only one exclamation mark. But making a compat function 
abort with valid input parameters strikes me as a bad idea.

> +            errno = ENOTSUP;

...and AFAIK, that's not a permitted error in this case.

You could handle the case that the RTC was shifted backward just fine.
And if it was shifted forward, returning late is permissible.

> +            return -1;
> +        }
> +
> +        // Get current time with requested clock
> +        if (clock_gettime(clock_id, &ts_now) != 0)
> +            return -1;
> +
> +        // Calculate relative timespec
> +        timespecs_sub(rqtp, &ts_now, &ts_rel);
> +
> +        // Check if time already elapsed
> +        if (ts_rel.tv_sec < 0 || timespec_zero(&ts_rel)) {
> +            pthread_testcancel();
> +            return 0;
> +        }
> +    } else if (flags == 0) {
> +        ts_rel = *rqtp;
> +    } else {
> +        // Invalid flags
> +        errno = EINVAL;
> +        return -1;
> +    }
> +
> +    switch (clock_id) {
> +        case CLOCK_MONOTONIC:
> +        case CLOCK_REALTIME:
> +            return nanosleep(&ts_rel, rmtp);
> +        default:
> +            // Invalid clock
> +            errno = EINVAL;
> +            return -1;
> +    }
> +
> +    assert(0);
> +    return -1;
> +}
> diff --git a/configure.ac b/configure.ac
> index 134cae50a6..c20ab3c75c 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -181,7 +181,9 @@ case "${host_os}" in
> 
>      dnl macOS 10.11 lacks clock_gettime, introduced with 10.12
>      AC_LIBOBJ([clock_gettime])
> -    AC_CHECK_FUNCS([clock_gettime])
> +    dnl macOS lacks clock_nanosleep
> +    AC_LIBOBJ([clock_nanosleep])
> +    AC_CHECK_FUNCS([clock_gettime clock_nanosleep])
> 
>      AC_EGREP_CPP(yes,
>              [#import <TargetConditionals.h>
> diff --git a/include/vlc_fixups.h b/include/vlc_fixups.h
> index 055bcf84d6..a296db0c32 100644
> --- a/include/vlc_fixups.h
> +++ b/include/vlc_fixups.h
> @@ -660,6 +660,9 @@ FILE *vlc_win32_tmpfile(void);
>  # define fdatasync fsync
> 
>  # include <time.h>
> +# ifndef TIMER_ABSTIME
> +#  define TIMER_ABSTIME 0x01
> +# endif
>  # ifndef CLOCK_REALTIME
>  #  define CLOCK_REALTIME 0
>  # endif
> @@ -669,6 +672,10 @@ FILE *vlc_win32_tmpfile(void);
>  # ifndef HAVE_CLOCK_GETTIME
>  int clock_gettime(clockid_t clock_id, struct timespec *tp);
>  # endif
> +# ifndef HAVE_CLOCK_NANOSLEEP
> +int clock_nanosleep(clockid_t clock_id, int flags,
> +        const struct timespec *rqtp, struct timespec *rmtp);
> +# endif
>  #endif
> 
>  #ifdef __cplusplus


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