src/shims/time.h

   1 /*
   2  * Copyright (c) 2008-2011 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_APACHE_LICENSE_HEADER_START@
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  *
  18  * @APPLE_APACHE_LICENSE_HEADER_END@
  19  */
  20
  21 /*
  22  * IMPORTANT: This header file describes INTERNAL interfaces to libdispatch
  23  * which are subject to change in future releases of Mac OS X. Any applications
  24  * relying on these interfaces WILL break.
  25  */
  26
  27 #ifndef __DISPATCH_SHIMS_TIME__
  28 #define __DISPATCH_SHIMS_TIME__
  29
  30 #ifndef __DISPATCH_INDIRECT__
  31 #error "Please #include <dispatch/dispatch.h> instead of this file directly."
  32 #endif
  33
  34 uint64_t _dispatch_get_nanoseconds(void);
  35
  36 #if defined(__i386__) || defined(__x86_64__) || !HAVE_MACH_ABSOLUTE_TIME
  37 // x86 currently implements mach time in nanoseconds
  38 // this is NOT likely to change
  39 #define _dispatch_time_mach2nano(x) ({x;})
  40 #define _dispatch_time_nano2mach(x) ({x;})
  41 #else
  42 typedef struct _dispatch_host_time_data_s {
  43         long double frac;
  44         bool ratio_1_to_1;
  45         dispatch_once_t pred;
  46 } _dispatch_host_time_data_s;
  47 extern _dispatch_host_time_data_s _dispatch_host_time_data;
  48 void _dispatch_get_host_time_init(void *context);
  49
  50 static inline uint64_t
  51 _dispatch_time_mach2nano(uint64_t machtime)
  52 {
  53         _dispatch_host_time_data_s *const data = &_dispatch_host_time_data;
  54         dispatch_once_f(&data->pred, NULL, _dispatch_get_host_time_init);
  55
  56         return machtime * data->frac;
  57 }
  58
  59 static inline int64_t
  60 _dispatch_time_nano2mach(int64_t nsec)
  61 {
  62         _dispatch_host_time_data_s *const data = &_dispatch_host_time_data;
  63         dispatch_once_f(&data->pred, NULL, _dispatch_get_host_time_init);
  64
  65         if (slowpath(_dispatch_host_time_data.ratio_1_to_1)) {
  66                 return nsec;
  67         }
  68
  69         long double big_tmp = nsec;
  70
  71         // Divide by tbi.numer/tbi.denom to convert nsec to Mach absolute time
  72         big_tmp /= data->frac;
  73
  74         // Clamp to a 64bit signed int
  75         if (slowpath(big_tmp > INT64_MAX)) {
  76                 return INT64_MAX;
  77         }
  78         if (slowpath(big_tmp < INT64_MIN)) {
  79                 return INT64_MIN;
  80         }
  81         return big_tmp;
  82 }
  83 #endif
  84
  85 static inline uint64_t
  86 _dispatch_absolute_time(void)
  87 {
  88 #if !HAVE_MACH_ABSOLUTE_TIME
  89         struct timespec ts;
  90         int ret;
  91
  92 #if HAVE_DECL_CLOCK_UPTIME
  93         ret = clock_gettime(CLOCK_UPTIME, &ts);
  94 #elif HAVE_DECL_CLOCK_MONOTONIC
  95         ret = clock_gettime(CLOCK_MONOTONIC, &ts);
  96 #else
  97 #error "clock_gettime: no supported absolute time clock"
  98 #endif
  99         (void)dispatch_assume_zero(ret);
 100
 101         /* XXXRW: Some kind of overflow detection needed? */
 102         return (ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec);
 103 #else
 104         return mach_absolute_time();
 105 #endif
 106 }
 107
 108 #endif