| 1 | /* |
| 2 | * SPDX-License-Identifier: MIT |
| 3 | * |
| 4 | * Copyright (C) 2010-2019 EfficiOS Inc. and Linux Foundation |
| 5 | */ |
| 6 | |
| 7 | #ifndef BABELTRACE2_TRACE_IR_CLOCK_SNAPSHOT_H |
| 8 | #define BABELTRACE2_TRACE_IR_CLOCK_SNAPSHOT_H |
| 9 | |
| 10 | #ifndef __BT_IN_BABELTRACE_H |
| 11 | # error "Please include <babeltrace2/babeltrace.h> instead." |
| 12 | #endif |
| 13 | |
| 14 | #include <stdint.h> |
| 15 | |
| 16 | #include <babeltrace2/types.h> |
| 17 | |
| 18 | #ifdef __cplusplus |
| 19 | extern "C" { |
| 20 | #endif |
| 21 | |
| 22 | /*! |
| 23 | @defgroup api-tir-cs Clock snapshot |
| 24 | @ingroup api-tir |
| 25 | |
| 26 | @brief |
| 27 | Snapshot of a \bt_stream clock. |
| 28 | |
| 29 | A <strong><em>clock snapshot</em></strong> is a snapshot of the value |
| 30 | of a \bt_stream clock (a \bt_clock_cls instance). |
| 31 | |
| 32 | A clock snapshot is a \ref api-tir "trace IR" data object. |
| 33 | |
| 34 | <em>Stream clocks</em> only exist conceptually in \bt_name because they |
| 35 | are stateful objects. \bt_cp_msg cannot refer to stateful objects |
| 36 | because they must not change while being transported from one |
| 37 | \bt_comp to the other. |
| 38 | |
| 39 | Instead of having a stream clock object, messages have a default |
| 40 | clock snapshot: this is a snapshot of the value of a stream's |
| 41 | default clock (a clock class instance): |
| 42 | |
| 43 | @image html clocks.png |
| 44 | |
| 45 | In the illustration above, notice that: |
| 46 | |
| 47 | - Each stream has a default clock (yellow bell alarm clock): this is an |
| 48 | instance of the stream's class's default clock class. |
| 49 | - Each \bt_msg (objects in blue stream rectangles) created for a given |
| 50 | stream has a default clock snapshot (yellow star): this is a snapshot |
| 51 | of the stream's default clock. |
| 52 | |
| 53 | In other words, a default clock snapshot contains the value of the |
| 54 | stream's default clock when this message occurred. |
| 55 | |
| 56 | A clock snapshot is a \ref api-fund-unique-object "unique object": it |
| 57 | belongs to a \bt_msg. |
| 58 | |
| 59 | The type of a clock snapshot is #bt_clock_snapshot. |
| 60 | |
| 61 | You cannot create a clock snapshot: you specify a clock snapshot value |
| 62 | (in clock cycles, a \c uint64_t value) when you create a \bt_msg or set |
| 63 | a message's clock snapshot with one of: |
| 64 | |
| 65 | - bt_message_stream_beginning_set_default_clock_snapshot() |
| 66 | - bt_message_stream_end_set_default_clock_snapshot() |
| 67 | - bt_message_event_create_with_default_clock_snapshot() |
| 68 | - bt_message_event_create_with_packet_and_default_clock_snapshot() |
| 69 | - bt_message_packet_beginning_create_with_default_clock_snapshot() |
| 70 | - bt_message_packet_end_create_with_default_clock_snapshot() |
| 71 | - bt_message_discarded_events_create_with_default_clock_snapshots() |
| 72 | - bt_message_discarded_packets_create_with_default_clock_snapshots() |
| 73 | - bt_message_message_iterator_inactivity_create() |
| 74 | |
| 75 | See \ref api-tir-clock-cls-origin "Clock value vs. clock class origin" |
| 76 | to understand the meaning of a clock's value in relation to the |
| 77 | properties of its class. |
| 78 | */ |
| 79 | |
| 80 | /*! @{ */ |
| 81 | |
| 82 | /*! |
| 83 | @name Type |
| 84 | @{ |
| 85 | |
| 86 | @typedef struct bt_clock_snapshot bt_clock_snapshot; |
| 87 | |
| 88 | @brief |
| 89 | Clock snapshot. |
| 90 | |
| 91 | @} |
| 92 | */ |
| 93 | |
| 94 | /*! |
| 95 | @brief |
| 96 | Borrows the \ref api-tir-clock-cls "class" of the clock of which |
| 97 | \bt_p{clock_snapshot} is a snapshot. |
| 98 | |
| 99 | @param[in] clock_snapshot |
| 100 | Clock snapshot of which to borrow the clock class. |
| 101 | |
| 102 | @returns |
| 103 | \em Borrowed reference of the clock class of \bt_p{clock_snapshot}. |
| 104 | |
| 105 | @bt_pre_not_null{clock_snapshot} |
| 106 | */ |
| 107 | extern const bt_clock_class *bt_clock_snapshot_borrow_clock_class_const( |
| 108 | const bt_clock_snapshot *clock_snapshot); |
| 109 | |
| 110 | /*! |
| 111 | @brief |
| 112 | Returns the value, in clock cycles, of the clock snapshot |
| 113 | \bt_p{clock_snapshot}. |
| 114 | |
| 115 | @param[in] clock_snapshot |
| 116 | Clock snapshot of which to get the value. |
| 117 | |
| 118 | @returns |
| 119 | Value of \bt_p{clock_snapshot} (clock cycles). |
| 120 | |
| 121 | @bt_pre_not_null{clock_snapshot} |
| 122 | |
| 123 | @sa bt_clock_snapshot_get_ns_from_origin() — |
| 124 | Returns the equivalent nanoseconds from clock class origin of a |
| 125 | clock snapshot's value. |
| 126 | */ |
| 127 | extern uint64_t bt_clock_snapshot_get_value( |
| 128 | const bt_clock_snapshot *clock_snapshot); |
| 129 | |
| 130 | /*! |
| 131 | @brief |
| 132 | Status codes for bt_clock_snapshot_get_ns_from_origin(). |
| 133 | */ |
| 134 | typedef enum bt_clock_snapshot_get_ns_from_origin_status { |
| 135 | /*! |
| 136 | @brief |
| 137 | Success. |
| 138 | */ |
| 139 | BT_CLOCK_SNAPSHOT_GET_NS_FROM_ORIGIN_STATUS_OK = __BT_FUNC_STATUS_OK, |
| 140 | |
| 141 | /*! |
| 142 | @brief |
| 143 | Integer overflow while computing the result. |
| 144 | */ |
| 145 | BT_CLOCK_SNAPSHOT_GET_NS_FROM_ORIGIN_STATUS_OVERFLOW_ERROR = __BT_FUNC_STATUS_OVERFLOW_ERROR, |
| 146 | } bt_clock_snapshot_get_ns_from_origin_status; |
| 147 | |
| 148 | /*! |
| 149 | @brief |
| 150 | Converts the value of the clock snapshot |
| 151 | \bt_p{clock_snapshot} from cycles to nanoseconds from the |
| 152 | \ref api-tir-clock-cls-origin "origin" of its |
| 153 | \bt_clock_cls and sets \bt_p{*ns_from_origin} to the result. |
| 154 | |
| 155 | This function: |
| 156 | |
| 157 | -# Converts the |
| 158 | \link api-tir-clock-cls-prop-offset "offset in cycles"\endlink |
| 159 | property of the clock class of \bt_p{clock_snapshot} to |
| 160 | seconds using its |
| 161 | \ref api-tir-clock-cls-prop-freq "frequency". |
| 162 | -# Converts the value of \bt_p{clock_snapshot} to seconds using the |
| 163 | frequency of its clock class. |
| 164 | -# Adds the values of 1., 2., and the |
| 165 | \link api-tir-clock-cls-prop-offset "offset in seconds"\endlink |
| 166 | property of the clock class of \bt_p{clock_snapshot}. |
| 167 | -# Converts the value of 3. to nanoseconds and sets |
| 168 | \bt_p{*ns_from_origin} to this result. |
| 169 | |
| 170 | The following illustration shows the possible scenarios: |
| 171 | |
| 172 | @image html clock-terminology.png |
| 173 | |
| 174 | This function can fail and return the |
| 175 | #BT_CLOCK_SNAPSHOT_GET_NS_FROM_ORIGIN_STATUS_OVERFLOW_ERROR status |
| 176 | code if any step of the computation process causes an integer overflow. |
| 177 | |
| 178 | @param[in] clock_snapshot |
| 179 | Clock snapshot containing the value to convert to nanoseconds |
| 180 | from the origin of its clock class. |
| 181 | @param[out] ns_from_origin |
| 182 | <strong>On success</strong>, \bt_p{*ns_from_origin} is the value |
| 183 | of \bt_p{clock_snapshot} converted to nanoseconds from the origin |
| 184 | of its clock class. |
| 185 | |
| 186 | @retval #BT_CLOCK_SNAPSHOT_GET_NS_FROM_ORIGIN_STATUS_OK |
| 187 | Success. |
| 188 | @retval #BT_CLOCK_SNAPSHOT_GET_NS_FROM_ORIGIN_STATUS_OVERFLOW_ERROR |
| 189 | Integer overflow while computing the result. |
| 190 | |
| 191 | @bt_pre_not_null{clock_snapshot} |
| 192 | @bt_pre_not_null{ns_from_origin} |
| 193 | |
| 194 | @sa bt_util_clock_cycles_to_ns_from_origin() — |
| 195 | Converts a clock value from cycles to nanoseconds from the clock's |
| 196 | origin. |
| 197 | @sa bt_clock_class_cycles_to_ns_from_origin() — |
| 198 | Converts a clock value from cycles to nanoseconds from a clock |
| 199 | class's origin. |
| 200 | */ |
| 201 | extern bt_clock_snapshot_get_ns_from_origin_status |
| 202 | bt_clock_snapshot_get_ns_from_origin( |
| 203 | const bt_clock_snapshot *clock_snapshot, |
| 204 | int64_t *ns_from_origin); |
| 205 | |
| 206 | /*! @} */ |
| 207 | |
| 208 | #ifdef __cplusplus |
| 209 | } |
| 210 | #endif |
| 211 | |
| 212 | #endif /* BABELTRACE2_TRACE_IR_CLOCK_SNAPSHOT_H */ |