src/util/os_time.h

   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@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_ */