1 //===-- SelectHelper.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_UTILITY_SELECTHELPER_H
10 #define LLDB_UTILITY_SELECTHELPER_H
11 
12 #include "lldb/Utility/Status.h"
13 #include "lldb/lldb-types.h"
14 
15 #include "llvm/ADT/DenseMap.h"
16 
17 #include <chrono>
18 #include <optional>
19 
20 class SelectHelper {
21 public:
22   // Defaults to infinite wait for select unless you call SetTimeout()
23   SelectHelper();
24 
25   // Call SetTimeout() before calling SelectHelper::Select() to set the timeout
26   // based on the current time + the timeout. This allows multiple calls to
27   // SelectHelper::Select() without having to worry about the absolute timeout
28   // as this class manages to set the relative timeout correctly.
29   void SetTimeout(const std::chrono::microseconds &timeout);
30 
31   // Call the FDSet*() functions before calling SelectHelper::Select() to set
32   // the file descriptors that we will watch for when calling select. This will
33   // cause FD_SET() to be called prior to calling select using the "fd"
34   // provided.
35   void FDSetRead(lldb::socket_t fd);
36   void FDSetWrite(lldb::socket_t fd);
37   void FDSetError(lldb::socket_t fd);
38 
39   // Call the FDIsSet*() functions after calling SelectHelper::Select() to
40   // check which file descriptors are ready for read/write/error. This will
41   // contain the result of FD_ISSET after calling select for a given file
42   // descriptor.
43   bool FDIsSetRead(lldb::socket_t fd) const;
44   bool FDIsSetWrite(lldb::socket_t fd) const;
45   bool FDIsSetError(lldb::socket_t fd) const;
46 
47   // Call the system's select() to wait for descriptors using timeout provided
48   // in a call the SelectHelper::SetTimeout(), or infinite wait if no timeout
49   // was set.
50   lldb_private::Status Select();
51 
52 protected:
53   struct FDInfo {
FDInfoFDInfo54     FDInfo()
55         : read_set(false), write_set(false), error_set(false),
56           read_is_set(false), write_is_set(false), error_is_set(false) {}
57 
PrepareForSelectFDInfo58     void PrepareForSelect() {
59       read_is_set = false;
60       write_is_set = false;
61       error_is_set = false;
62     }
63 
64     bool read_set : 1, write_set : 1, error_set : 1, read_is_set : 1,
65         write_is_set : 1, error_is_set : 1;
66   };
67   llvm::DenseMap<lldb::socket_t, FDInfo> m_fd_map;
68   std::optional<std::chrono::steady_clock::time_point> m_end_time;
69 };
70 
71 #endif // LLDB_UTILITY_SELECTHELPER_H
72