include/babeltrace/context.h

   1 #ifndef _BABELTRACE_CONTEXT_H
   2 #define _BABELTRACE_CONTEXT_H
   3
   4 /*
   5  * BabelTrace
   6  *
   7  * context header
   8  *
   9  * Copyright 2012 EfficiOS Inc. and Linux Foundation
  10  *
  11  * Author: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  12  *         Julien Desfossez <julien.desfossez@efficios.com>
  13  *
  14  * Permission is hereby granted, free of charge, to any person obtaining
  15  * a copy of this software and associated documentation files (the
  16  * "Software"), to deal in the Software without restriction, including
  17  * without limitation the rights to use, copy, modify, merge, publish,
  18  * distribute, sublicense, and/or sell copies of the Software, and to
  19  * permit persons to whom the Software is furnished to do so, subject to
  20  * the following conditions:
  21  *
  22  * The above copyright notice and this permission notice shall be
  23  * included in all copies or substantial portions of the Software.
  24  */
  25
  26 #include <unistd.h>
  27 #include <babeltrace/format.h>
  28
  29 /* struct bt_context is opaque to the user */
  30 struct bt_context;
  31 struct stream_pos;
  32
  33 /*
  34  * bt_context_create : create a Babeltrace context
  35  *
  36  * Allocate a new context. The creation of the context sets the refcount
  37  * to 1.
  38  *
  39  * Returns an allocated context on success and NULL on error
  40  */
  41 struct bt_context *bt_context_create(void);
  42
  43 /*
  44  * bt_context_add_trace : Add a trace by path to the context
  45  *
  46  * Open a trace.
  47  *
  48  * packet_seek can be NULL to use the default packet_seek handler
  49  * provided by the trace format. If non-NULL, it is used as an override
  50  * of the handler for seeks across packets. It takes as parameter a
  51  * stream position, the packet index it needs to seek to (for SEEK_SET),
  52  * and a "whence" parameter (either SEEK_CUR: seek to next packet, or
  53  * SEEK_SET: seek to packet at packet index).
  54  *
  55  * If "path" is NULL, stream_list is used instread as a list of streams
  56  * to open for the trace.
  57
  58  * The metadata parameter acts as a metadata override when not NULL.
  59  *
  60  * Return: the trace handle id (>= 0) on success, a negative
  61  * value on error.
  62  */
  63 int bt_context_add_trace(struct bt_context *ctx, const char *path,
  64                 const char *format,
  65                 void (*packet_seek)(struct stream_pos *pos,
  66                         size_t index, int whence),
  67                 struct mmap_stream_list *stream_list,
  68                 FILE *metadata);
  69
  70 /*
  71  * bt_context_remove_trace: Remove a trace from the context.
  72  *
  73  * Effectively closing the trace.
  74  */
  75 void bt_context_remove_trace(struct bt_context *ctx, int trace_id);
  76
  77 /*
  78  * bt_context_get and bt_context_put : increments and decrement the
  79  * refcount of the context
  80  *
  81  * These functions ensures that the context won't be destroyed when it
  82  * is in use. The same number of get and put (plus one extra put to
  83  * release the initial reference done at creation) has to be done to
  84  * destroy a context.
  85  *
  86  * When the context refcount is decremented to 0 by a bt_context_put,
  87  * the context is freed.
  88  */
  89 void bt_context_get(struct bt_context *ctx);
  90 void bt_context_put(struct bt_context *ctx);
  91
  92 #endif /* _BABELTRACE_CONTEXT_H */