Home | History | Annotate | Download | only in util 
      1 /**************************************************************************
      2  *
      3  * Copyright 2008-2010 VMware, Inc.
      4  * All Rights Reserved.
      5  *
      6  * Permission is hereby granted, free of charge, to any person obtaining a
      7  * copy of this software and associated documentation files (the
      8  * "Software"), to deal in the Software without restriction, including
      9  * without limitation the rights to use, copy, modify, merge, publish,
     10  * distribute, sub license, and/or sell copies of the Software, and to
     11  * permit persons to whom the Software is furnished to do so, subject to
     12  * the following conditions:
     13  *
     14  * The above copyright notice and this permission notice (including the
     15  * next paragraph) shall be included in all copies or substantial portions
     16  * of the Software.
     17  *
     18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
     19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
     20  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
     21  * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
     22  * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
     23  * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
     24  * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
     25  *
     26  **************************************************************************/
     27 
     28 /**
     29  * @file
     30  * OS independent time-manipulation functions.
     31  *
     32  * @author Jose Fonseca <jfonseca (at) vmware.com>
     33  */
     34 
     35 #ifndef _OS_TIME_H_
     36 #define _OS_TIME_H_
     37 
     38 #include <stdbool.h>
     39 #include <stdint.h>
     40 
     41 #ifdef __cplusplus
     42 extern "C" {
     43 #endif
     44 
     45 /* must be equal to PIPE_TIMEOUT_INFINITE */
     46 #define OS_TIMEOUT_INFINITE 0xffffffffffffffffull
     47 
     48 /*
     49  * Get the current time in nanoseconds from an unknown base.
     50  */
     51 int64_t
     52 os_time_get_nano(void);
     53 
     54 
     55 /*
     56  * Get the current time in microseconds from an unknown base.
     57  */
     58 static inline int64_t
     59 os_time_get(void)
     60 {
     61    return os_time_get_nano() / 1000;
     62 }
     63 
     64 
     65 /*
     66  * Sleep.
     67  */
     68 void
     69 os_time_sleep(int64_t usecs);
     70 
     71 
     72 /*
     73  * Helper function for detecting time outs, taking in account overflow.
     74  *
     75  * Returns true if the current time has elapsed beyond the specified interval.
     76  */
     77 static inline bool
     78 os_time_timeout(int64_t start,
     79                 int64_t end,
     80                 int64_t curr)
     81 {
     82    if (start <= end)
     83       return !(start <= curr && curr < end);
     84    else
     85       return !((start <= curr) || (curr < end));
     86 }
     87 
     88 
     89 /**
     90  * Convert a relative timeout in nanoseconds into an absolute timeout,
     91  * in other words, it returns current time + timeout.
     92  * os_time_get_nano() must be monotonic.
     93  * OS_TIMEOUT_INFINITE is passed through unchanged. If the calculation
     94  * overflows, OS_TIMEOUT_INFINITE is returned.
     95  */
     96 int64_t
     97 os_time_get_absolute_timeout(uint64_t timeout);
     98 
     99 
    100 /**
    101  * Wait until the variable at the given memory location is zero.
    102  *
    103  * \param var           variable
    104  * \param timeout       timeout in ns, can be anything from 0 (no wait) to
    105  *                      OS_TIMEOUT_INFINITE (wait forever)
    106  * \return     true if the variable is zero
    107  */
    108 bool
    109 os_wait_until_zero(volatile int *var, uint64_t timeout);
    110 
    111 
    112 /**
    113  * Wait until the variable at the given memory location is zero.
    114  * The timeout is the absolute time when the waiting should stop. If it is
    115  * less than or equal to the current time, it only returns the status and
    116  * doesn't wait. OS_TIMEOUT_INFINITE waits forever. This requires that
    117  * os_time_get_nano is monotonic.
    118  *
    119  * \param var       variable
    120  * \param timeout   the time in ns when the waiting should stop
    121  * \return     true if the variable is zero
    122  */
    123 bool
    124 os_wait_until_zero_abs_timeout(volatile int *var, int64_t timeout);
    125 
    126 #ifdef __cplusplus
    127 }
    128 #endif
    129 
    130 #endif /* _OS_TIME_H_ */
    131