compat.c

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/*
 * Compatibility functions
 */

#include "compat.h"
#include <sys/types.h>          /* off_t, size_t */
#include <unistd.h>             /* fdatasync(), if available */


/*
 * sync_file_range() support through an internal similar API
 */

#ifdef LACK_SYNC_FILE_RANGE
#warning "Using fdatasync() instead of sync_file_range()"
const int have_sync_range = 0;

int sync_range_submit(int fd, off_t offset, size_t nbytes)
{
        return 0;
}

int sync_range_wait(int fd, off_t offset, size_t nbytes)
{
        /* fdatasync() waits for the submitted I/O to complete, so it's enough
         * to call it once here */
        return fdatasync(fd);
}

#else

const int have_sync_range = 1;

int sync_range_submit(int fd, off_t offset, size_t nbytes)
{
        /* We don't need SYNC_FILE_RANGE_WAIT_BEFORE because we have exclusive
         * access to the range (guaranteed by the caller) */
        return sync_file_range(fd, offset, nbytes, SYNC_FILE_RANGE_WRITE);
}

int sync_range_wait(int fd, off_t offset, size_t nbytes)
{
        return sync_file_range(fd, offset, nbytes, SYNC_FILE_RANGE_WAIT_BEFORE);
}

#endif /* defined LACK_SYNC_FILE_RANGE */


/* When posix_fadvise() is not available, we just show a message since there
 * is no alternative implementation */
#ifdef LACK_POSIX_FADVISE
#warning "Not using posix_fadvise()"
#endif


/*
 * Support for platforms where clock_gettime() is not available.
 */

#ifdef LACK_CLOCK_GETTIME
#warning "Using gettimeofday() instead of clock_gettime()"

#include <sys/time.h>           /* gettimeofday() */

int clock_gettime(int clk_id, struct timespec *tp)
{
        struct timeval tv;

        gettimeofday(&tv, NULL);

        tp->tv_sec = tv.tv_sec;
        tp->tv_nsec = tv.tv_usec / 1000.0;

        return 0;
}

#endif /* defined LACK_CLOCK_GETTIME */


#ifdef LACK_FDATASYNC
#warning "Using fsync() instead of fdatasync()"

#include <unistd.h>             /* fsync() */

int fdatasync(int fd)
{
        return fsync(fd);
}
#endif /* defined LACK_FDATASYNC */

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