include/babeltrace/iterator.h

   1 #ifndef _BABELTRACE_ITERATOR_H
   2 #define _BABELTRACE_ITERATOR_H
   3
   4 /*
   5  * BabelTrace API Iterators
   6  *
   7  * Copyright 2010-2011 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   8  *
   9  * Permission is hereby granted, free of charge, to any person obtaining a copy
  10  * of this software and associated documentation files (the "Software"), to deal
  11  * in the Software without restriction, including without limitation the rights
  12  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13  * copies of the Software, and to permit persons to whom the Software is
  14  * furnished to do so, subject to the following conditions:
  15  *
  16  * The above copyright notice and this permission notice shall be included in
  17  * all copies or substantial portions of the Software.
  18  */
  19
  20 #include <babeltrace/format.h>
  21 #include <babeltrace/context.h>
  22
  23 /* Forward declarations */
  24 struct bt_iter;
  25 struct bt_saved_pos;
  26
  27 /*
  28  * bt_iter is an abstract class, each format has to implement its own
  29  * iterator derived from this parent class.
  30  */
  31
  32 /*
  33  * bt_iter_pos
  34  *
  35  * This structure represents the position where to set an iterator.
  36  *
  37  * type represents the type of seek to use.
  38  * u is the argument of the seek if necessary :
  39  * - seek_time is the real timestamp to seek to when using BT_SEEK_TIME, it
  40  *   is expressed in nanoseconds
  41  * - restore is a position saved with bt_iter_get_pos, it is used with
  42  *   BT_SEEK_RESTORE.
  43  *
  44  * Note about BT_SEEK_LAST: if many events happen to be at the last
  45  * timestamp, it is implementation-defined which event will be the last,
  46  * and the order of events with the same timestamp may not be the same
  47  * as normal iteration on the trace. Therefore, it is recommended to
  48  * only use BT_SEEK_LAST to get the timestamp of the last event(s) in
  49  * the trace.
  50  */
  51 struct bt_iter_pos {
  52         enum {
  53                 BT_SEEK_TIME,           /* uses u.seek_time */
  54                 BT_SEEK_RESTORE,        /* uses u.restore */
  55                 BT_SEEK_CUR,
  56                 BT_SEEK_BEGIN,
  57                 BT_SEEK_END,
  58                 BT_SEEK_LAST,
  59         } type;
  60         union {
  61                 uint64_t seek_time;
  62                 struct bt_saved_pos *restore;
  63         } u;
  64 };
  65
  66 /*
  67  * bt_iter_next: Move trace collection position to the next event.
  68  *
  69  * Returns 0 on success, a negative value on error
  70  */
  71 int bt_iter_next(struct bt_iter *iter);
  72
  73 /*
  74  * bt_iter_get_pos - Get the current iterator position.
  75  *
  76  * The position returned by this function needs to be freed by
  77  * bt_iter_free_pos after use.
  78  */
  79 struct bt_iter_pos *bt_iter_get_pos(struct bt_iter *iter);
  80
  81 /*
  82  * bt_iter_free_pos - Free the position.
  83  */
  84 void bt_iter_free_pos(struct bt_iter_pos *pos);
  85
  86 /*
  87  * bt_iter_set_pos: move the iterator to a given position.
  88  *
  89  * On error, the stream_heap is reinitialized and returned empty.
  90  *
  91  * Return 0 for success.
  92  *
  93  * Return EOF if the position requested is after the last event of the
  94  * trace collection.
  95  * Return -EINVAL when called with invalid parameter.
  96  * Return -ENOMEM if the stream_heap could not be properly initialized.
  97  */
  98 int bt_iter_set_pos(struct bt_iter *iter, const struct bt_iter_pos *pos);
  99
 100 /*
 101  * bt_iter_create_time_pos: create a position based on time
 102  *
 103  * This function allocates and returns a new bt_iter_pos (which must be freed
 104  * with bt_iter_free_pos) to be able to restore an iterator position based on a
 105  * real timestamp.
 106  */
 107 struct bt_iter_pos *bt_iter_create_time_pos(struct bt_iter *iter,
 108                 uint64_t timestamp);
 109
 110 #endif /* _BABELTRACE_ITERATOR_H */