1//===-- SBTraceCursor.h -----------------------------------------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8
9#ifndef LLDB_API_SBTRACECURSOR_H
10#define LLDB_API_SBTRACECURSOR_H
11
12#include "lldb/API/SBDefines.h"
13#include "lldb/API/SBError.h"
14#include "lldb/API/SBExecutionContext.h"
15
16namespace lldb {
17
18class LLDB_API SBTraceCursor {
19public:
20  /// Default constructor for an invalid \a SBTraceCursor object.
21  SBTraceCursor();
22
23  /// Set the direction to use in the \a SBTraceCursor::Next() method.
24  ///
25  /// \param[in] forwards
26  ///     If \b true, then the traversal will be forwards, otherwise backwards.
27  void SetForwards(bool forwards);
28
29  /// Check if the direction to use in the \a SBTraceCursor::Next() method is
30  /// forwards.
31  ///
32  /// \return
33  ///     \b true if the current direction is forwards, \b false if backwards.
34  bool IsForwards() const;
35
36  /// Move the cursor to the next item (instruction or error).
37  ///
38  /// Direction:
39  ///     The traversal is done following the current direction of the trace. If
40  ///     it is forwards, the instructions are visited forwards
41  ///     chronologically. Otherwise, the traversal is done in
42  ///     the opposite direction. By default, a cursor moves backwards unless
43  ///     changed with \a SBTraceCursor::SetForwards().
44  void Next();
45
46  /// \return
47  ///     \b true if the cursor is pointing to a valid item. \b false if the
48  ///     cursor has reached the end of the trace.
49  bool HasValue() const;
50
51  /// Instruction identifiers:
52  ///
53  /// When building complex higher level tools, fast random accesses in the
54  /// trace might be needed, for which each instruction requires a unique
55  /// identifier within its thread trace. For example, a tool might want to
56  /// repeatedly inspect random consecutive portions of a trace. This means that
57  /// it will need to first move quickly to the beginning of each section and
58  /// then start its iteration. Given that the number of instructions can be in
59  /// the order of hundreds of millions, fast random access is necessary.
60  ///
61  /// An example of such a tool could be an inspector of the call graph of a
62  /// trace, where each call is represented with its start and end instructions.
63  /// Inspecting all the instructions of a call requires moving to its first
64  /// instruction and then iterating until the last instruction, which following
65  /// the pattern explained above.
66  ///
67  /// Instead of using 0-based indices as identifiers, each Trace plug-in can
68  /// decide the nature of these identifiers and thus no assumptions can be made
69  /// regarding their ordering and sequentiality. The reason is that an
70  /// instruction might be encoded by the plug-in in a way that hides its actual
71  /// 0-based index in the trace, but it's still possible to efficiently find
72  /// it.
73  ///
74  /// Requirements:
75  /// - For a given thread, no two instructions have the same id.
76  /// - In terms of efficiency, moving the cursor to a given id should be as
77  ///   fast as possible, but not necessarily O(1). That's why the recommended
78  ///   way to traverse sequential instructions is to use the \a
79  ///   SBTraceCursor::Next() method and only use \a SBTraceCursor::GoToId(id)
80  ///   sparingly.
81
82  /// Make the cursor point to the item whose identifier is \p id.
83  ///
84  /// \return
85  ///     \b true if the given identifier exists and the cursor effectively
86  ///     moved to it. Otherwise, \b false is returned and the cursor now points
87  ///     to an invalid item, i.e. calling \a HasValue() will return \b false.
88  bool GoToId(lldb::user_id_t id);
89
90  /// \return
91  ///     \b true if and only if there's an instruction item with the given \p
92  ///     id.
93  bool HasId(lldb::user_id_t id) const;
94
95  /// \return
96  ///     A unique identifier for the instruction or error this cursor is
97  ///     pointing to.
98  lldb::user_id_t GetId() const;
99  /// \}
100
101  /// Make the cursor point to an item in the trace based on an origin point and
102  /// an offset.
103  ///
104  /// The resulting position of the trace is
105  ///     origin + offset
106  ///
107  /// If this resulting position would be out of bounds, the trace then points
108  /// to an invalid item, i.e. calling \a HasValue() returns \b false.
109  ///
110  /// \param[in] offset
111  ///     How many items to move forwards (if positive) or backwards (if
112  ///     negative) from the given origin point. For example, if origin is \b
113  ///     End, then a negative offset would move backward in the trace, but a
114  ///     positive offset would move past the trace to an invalid item.
115  ///
116  /// \param[in] origin
117  ///     The reference point to use when moving the cursor.
118  ///
119  /// \return
120  ///     \b true if and only if the cursor ends up pointing to a valid item.
121  bool Seek(int64_t offset, lldb::TraceCursorSeekType origin);
122
123  /// Trace item information (instructions, errors and events)
124  /// \{
125
126  /// \return
127  ///     The kind of item the cursor is pointing at.
128  lldb::TraceItemKind GetItemKind() const;
129
130  /// \return
131  ///     Whether the cursor points to an error or not.
132  bool IsError() const;
133
134  /// \return
135  ///     The error message the cursor is pointing at.
136  const char *GetError() const;
137
138  /// \return
139  ///     Whether the cursor points to an event or not.
140  bool IsEvent() const;
141
142  /// \return
143  ///     The specific kind of event the cursor is pointing at.
144  lldb::TraceEvent GetEventType() const;
145
146  /// \return
147  ///     A human-readable description of the event this cursor is pointing at.
148  const char *GetEventTypeAsString() const;
149
150  /// \return
151  ///     Whether the cursor points to an instruction.
152  bool IsInstruction() const;
153
154  /// \return
155  ///     The load address of the instruction the cursor is pointing at.
156  lldb::addr_t GetLoadAddress() const;
157
158  /// \return
159  ///    The requested CPU id, or LLDB_INVALID_CPU_ID if this information is
160  ///    not available for the current item.
161  lldb::cpu_id_t GetCPU() const;
162
163  bool IsValid() const;
164
165  explicit operator bool() const;
166
167protected:
168  friend class SBTrace;
169
170  /// Create a cursor that initially points to the end of the trace, i.e. the
171  /// most recent item.
172  SBTraceCursor(lldb::TraceCursorSP trace_cursor_sp);
173
174  lldb::TraceCursorSP m_opaque_sp;
175};
176} // namespace lldb
177
178#endif // LLDB_API_SBTRACECURSOR_H
179