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 a copy
  15  * of this software and associated documentation files (the "Software"), to deal
  16  * in the Software without restriction, including without limitation the rights
  17  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  18  * copies of the Software, and to permit persons to whom the Software is
  19  * furnished to do so, subject to the following conditions:
  20  *
  21  * The above copyright notice and this permission notice shall be included in
  22  * all copies or substantial portions of the Software.
  23  */
  24
  25 struct trace_collection;
  26
  27 /*
  28  * The context represents the object in which a trace_collection is open. As
  29  * long as this structure is allocated, the trace_collection is open and the
  30  * traces it contains can be read and seeked by the iterators and callbacks.
  31  *
  32  * It has to be created with the bt_context_create() function and destroyed by
  33  * bt_context_destroy()
  34  */
  35 struct bt_context {
  36         struct trace_collection *tc;
  37         int refcount;
  38         int last_trace_handle_id;
  39 };
  40
  41 /*
  42  * bt_context_create : create a Babeltrace context
  43  *
  44  * Allocate a new context and assign the trace_collection passed in
  45  * parameter as the context trace_collection. The trace_collection
  46  * must contain an array of valid trace_descriptors. The creation of
  47  * the context sets the refcount to 1.
  48  *
  49  * Returns an allocated context on success and NULL on error
  50  */
  51 struct bt_context *bt_context_create(struct trace_collection *tc);
  52
  53 /*
  54  * bt_context_destroy : destroy a context
  55  *
  56  * If the context is still in use (by an iterator or a callback), the
  57  * destroy fails and returns -1, on success : return 0.
  58  */
  59 int bt_context_destroy(struct bt_context *ctx);
  60
  61 /*
  62  * bt_context_get and bt_context_put : increments and decrement the refcount of
  63  * the context
  64  *
  65  * These functions ensures that the context won't be destroyed when it is in
  66  * use. The same number of get and put has to be done to be able to destroy a
  67  * context.
  68  *
  69  * Return 0 on success, -1 if the context pointer is invalid.  When the context
  70  * refcount is decremented to 0 by a bt_context_put, it calls
  71  * bt_context_destroy to free the context. In this case the return code of
  72  * bt_context_destroy is returned.
  73  */
  74 int bt_context_get(struct bt_context *ctx);
  75 int bt_context_put(struct bt_context *ctx);
  76
  77 #endif /* _BABELTRACE_CONTEXT_H */