dispatch-1.0/src/shims/time.h

   1 /*
   2  * Copyright (c) 2008-2009 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 #if defined(__i386__) || defined(__x86_64__) || !defined(HAVE_MACH_ABSOLUTE_TIME)
  35 // these architectures always return mach_absolute_time() in nanoseconds
  36 #define _dispatch_time_mach2nano(x) (x)
  37 #define _dispatch_time_nano2mach(x) (x)
  38 #else
  39 typedef struct _dispatch_host_time_data_s {
  40         long double frac;
  41         bool ratio_1_to_1;
  42         dispatch_once_t pred;
  43 } _dispatch_host_time_data_s;
  44 __private_extern__ _dispatch_host_time_data_s _dispatch_host_time_data;
  45 __private_extern__ void _dispatch_get_host_time_init(void *context);
  46
  47 static inline uint64_t
  48 _dispatch_time_mach2nano(uint64_t machtime)
  49 {
  50         _dispatch_host_time_data_s *const data = &_dispatch_host_time_data;
  51         dispatch_once_f(&data->pred, NULL, _dispatch_get_host_time_init);
  52
  53         return (uint64_t)(machtime * data->frac);
  54 }
  55
  56 static inline int64_t
  57 _dispatch_time_nano2mach(int64_t nsec)
  58 {
  59         _dispatch_host_time_data_s *const data = &_dispatch_host_time_data;
  60         dispatch_once_f(&data->pred, NULL, _dispatch_get_host_time_init);
  61
  62         if (slowpath(_dispatch_host_time_data.ratio_1_to_1)) {
  63                 return nsec;
  64         }
  65
  66         long double big_tmp = (long double)nsec;
  67
  68         // Divide by tbi.numer/tbi.denom to convert nsec to Mach absolute time
  69         big_tmp /= data->frac;
  70
  71         // Clamp to a 64bit signed int
  72         if (slowpath(big_tmp > INT64_MAX)) {
  73                 return INT64_MAX;
  74         }
  75         if (slowpath(big_tmp < INT64_MIN)) {
  76                 return INT64_MIN;
  77         }
  78         return (int64_t)big_tmp;
  79 }
  80 #endif
  81
  82 static inline uint64_t
  83 _dispatch_absolute_time(void)
  84 {
  85 #if HAVE_MACH_ABSOLUTE_TIME
  86         return mach_absolute_time();
  87 #else
  88         struct timespec ts;
  89         int ret;
  90
  91 #if HAVE_DECL_CLOCK_UPTIME
  92         ret = clock_gettime(CLOCK_UPTIME, &ts);
  93 #elif HAVE_DECL_CLOCK_MONOTONIC
  94         ret = clock_gettime(CLOCK_MONOTONIC, &ts);
  95 #else
  96 #error "clock_gettime: no supported absolute time clock"
  97 #endif
  98         (void)dispatch_assume_zero(ret);
  99
 100         /* XXXRW: Some kind of overflow detection needed? */
 101         return (ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec);
 102 #endif
 103 }
 104
 105 #endif /* __DISPATCH_SHIMS_TIME__ */