bt_context_add_trace, bt_iter_pos and bt_iter needed some more comments.
[babeltrace.git] / 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 * path is the path to the trace, it is not recursive. If "path" is NULL,
49 * stream_list is used instead as a list of mmap streams to open for the trace.
50 *
51 * format is a string containing the format name in which the trace was
52 * produced.
53 *
54 * packet_seek can be NULL to use the default packet_seek handler provided by
55 * the trace format. If non-NULL, it is used as an override of the handler for
56 * seeks across packets. It takes as parameter a stream position, the packet
57 * index it needs to seek to (for SEEK_SET), and a "whence" parameter (either
58 * SEEK_CUR: seek to next packet, or SEEK_SET: seek to packet at packet index).
59 *
60 * stream_list is a linked list of streams, it is used to open a trace where
61 * the trace data is located in memory mapped areas instead of trace files,
62 * this argument should be set to NULL when path is not NULL.
63 *
64 * The metadata parameter acts as a metadata override when not NULL, otherwise
65 * the format handles the metadata opening.
66 *
67 * Return: the trace handle id (>= 0) on success, a negative
68 * value on error.
69 */
70 int bt_context_add_trace(struct bt_context *ctx, const char *path,
71 const char *format,
72 void (*packet_seek)(struct stream_pos *pos,
73 size_t index, int whence),
74 struct mmap_stream_list *stream_list,
75 FILE *metadata);
76
77 /*
78 * bt_context_remove_trace: Remove a trace from the context.
79 *
80 * Effectively closing the trace.
81 */
82 void bt_context_remove_trace(struct bt_context *ctx, int trace_id);
83
84 /*
85 * bt_context_get and bt_context_put : increments and decrement the
86 * refcount of the context
87 *
88 * These functions ensures that the context won't be destroyed when it
89 * is in use. The same number of get and put (plus one extra put to
90 * release the initial reference done at creation) has to be done to
91 * destroy a context.
92 *
93 * When the context refcount is decremented to 0 by a bt_context_put,
94 * the context is freed.
95 */
96 void bt_context_get(struct bt_context *ctx);
97 void bt_context_put(struct bt_context *ctx);
98
99 #endif /* _BABELTRACE_CONTEXT_H */
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