include/babeltrace2/util.h

   1 #ifndef BABELTRACE2_UTIL_H
   2 #define BABELTRACE2_UTIL_H
   3
   4 /*
   5  * Copyright (c) 2010-2019 EfficiOS Inc. and Linux Foundation
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a copy
   8  * of this software and associated documentation files (the "Software"), to deal
   9  * in the Software without restriction, including without limitation the rights
  10  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11  * copies of the Software, and to permit persons to whom the Software is
  12  * furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included in
  15  * all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23  * SOFTWARE.
  24  */
  25
  26 #ifndef __BT_IN_BABELTRACE_H
  27 # error "Please include <babeltrace2/babeltrace.h> instead."
  28 #endif
  29
  30 #include <stdint.h>
  31
  32 #ifdef __cplusplus
  33 extern "C" {
  34 #endif
  35
  36 /*!
  37 @defgroup api-util General purpose utilities
  38
  39 @brief
  40     General purpose utilities.
  41
  42 This module contains general purpose utilities.
  43 */
  44
  45 /*! @{ */
  46
  47 /*!
  48 @brief
  49     Status codes for bt_util_clock_cycles_to_ns_from_origin().
  50 */
  51 typedef enum bt_util_clock_cycles_to_ns_from_origin_status {
  52         /*!
  53         @brief
  54             Success.
  55         */
  56         BT_UTIL_CLOCK_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OK                = __BT_FUNC_STATUS_OK,
  57
  58         /*!
  59         @brief
  60             Integer overflow while computing the result.
  61         */
  62         BT_UTIL_CLOCK_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OVERFLOW_ERROR    = __BT_FUNC_STATUS_OVERFLOW_ERROR,
  63 } bt_util_clock_cycles_to_ns_from_origin_status;
  64
  65 /*!
  66 @brief
  67     Converts the clock value \bt_p{cycles} from cycles to nanoseconds
  68     from the clock's origin and sets \bt_p{*ns_from_origin} to the
  69     result.
  70
  71 This function considers the clock's frequency in Hz (\bt_p{frequency}),
  72 an offset from its origin in seconds (\bt_p{offset_seconds}) which
  73 can be negative, and an additional offset in cycles
  74 (\bt_p{offset_cycles}).
  75
  76 This function:
  77
  78 -# Converts the \bt_p{offset_cycles} value to seconds using
  79    \bt_p{frequency}.
  80 -# Converts the \bt_p{cycles} value to seconds using \bt_p{frequency}.
  81 -# Adds the values of 1., 2., and \bt_p{offset_seconds}.
  82 -# Converts the value of 3. to nanoseconds and sets
  83    \bt_p{*ns_from_origin} to this result.
  84
  85 The following illustration shows the possible scenarios:
  86
  87 @image html clock-terminology.png
  88
  89 \bt_p{offset_seconds} can be negative. For example, considering:
  90
  91 - A 1000&nbsp;Hz clock.
  92 - \bt_p{offset_seconds} set to -10&nbsp;seconds.
  93 - \bt_p{offset_cycles} set to 500&nbsp;cycles
  94   (that is, 0.5&nbsp;seconds).
  95 - \bt_p{cycles} set to 2000&nbsp;cycles (that is, 2&nbsp;seconds).
  96
  97 The computed value is -7.5&nbsp;seconds, so this function sets
  98 \bt_p{*ns_from_origin} to -7,500,000,000.
  99
 100 This function can fail and return the
 101 #BT_UTIL_CLOCK_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OVERFLOW_ERROR status
 102 code if any step of the computation process causes an integer overflow.
 103
 104 @param[in] cycles
 105     Clock's value (cycles).
 106 @param[in] frequency
 107     Clock's frequency (Hz, or cycles/second).
 108 @param[in] offset_seconds
 109     Offset, in seconds, from the clock's origin to add to
 110     \bt_p{cycles} (once converted to seconds).
 111 @param[in] offset_cycles
 112     Offset, in cycles, to add to \bt_p{cycles}.
 113 @param[out] ns_from_origin
 114     <strong>On success</strong>, \bt_p{*ns_from_origin} is \bt_p{cycles}
 115     converted to nanoseconds from origin considering the clock's
 116     properties.
 117
 118 @retval #BT_UTIL_CLOCK_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OK
 119     Success.
 120 @retval #BT_UTIL_CLOCK_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OVERFLOW_ERROR
 121     Integer overflow while computing the result.
 122
 123 @pre
 124     \bt_p{frequency} is not 0.
 125 @pre
 126     \bt_p{frequency} is not <code>UINT64_C(-1)</code>.
 127 @pre
 128     \bt_p{frequency} is greater than \bt_p{offset_cycles}.
 129 @pre
 130     \bt_p{offset_cycles} is less than \bt_p{frequency}.
 131 @bt_pre_not_null{ns_from_origin}
 132
 133 @sa bt_clock_class_cycles_to_ns_from_origin() &mdash;
 134     Converts a stream clock value from cycles to nanoseconds from the
 135     origin of a given clock class.
 136 */
 137 bt_util_clock_cycles_to_ns_from_origin_status
 138 bt_util_clock_cycles_to_ns_from_origin(uint64_t cycles,
 139                 uint64_t frequency, int64_t offset_seconds,
 140                 uint64_t offset_cycles, int64_t *ns_from_origin);
 141
 142 /*! @} */
 143
 144 #ifdef __cplusplus
 145 }
 146 #endif
 147
 148 #endif /* BABELTRACE2_UTIL_H */