| 1 | /* Observers |
| 2 | |
| 3 | Copyright (C) 2016-2020 Free Software Foundation, Inc. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 7 | This program is free software; you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation; either version 3 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program. If not, see <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | #ifndef COMMON_OBSERVABLE_H |
| 21 | #define COMMON_OBSERVABLE_H |
| 22 | |
| 23 | #include <algorithm> |
| 24 | #include <functional> |
| 25 | #include <vector> |
| 26 | |
| 27 | namespace gdb |
| 28 | { |
| 29 | |
| 30 | namespace observers |
| 31 | { |
| 32 | |
| 33 | extern unsigned int observer_debug; |
| 34 | |
| 35 | /* An observer is an entity which is interested in being notified |
| 36 | when GDB reaches certain states, or certain events occur in GDB. |
| 37 | The entity being observed is called the observable. To receive |
| 38 | notifications, the observer attaches a callback to the observable. |
| 39 | One observable can have several observers. |
| 40 | |
| 41 | The observer implementation is also currently not reentrant. In |
| 42 | particular, it is therefore not possible to call the attach or |
| 43 | detach routines during a notification. */ |
| 44 | |
| 45 | /* The type of a key that can be passed to attach, which can be passed |
| 46 | to detach to remove associated observers. Tokens have address |
| 47 | identity, and are thus usually const globals. */ |
| 48 | struct token |
| 49 | { |
| 50 | token () = default; |
| 51 | |
| 52 | DISABLE_COPY_AND_ASSIGN (token); |
| 53 | }; |
| 54 | |
| 55 | template<typename... T> |
| 56 | class observable |
| 57 | { |
| 58 | public: |
| 59 | |
| 60 | typedef std::function<void (T...)> func_type; |
| 61 | |
| 62 | explicit observable (const char *name) |
| 63 | : m_name (name) |
| 64 | { |
| 65 | } |
| 66 | |
| 67 | DISABLE_COPY_AND_ASSIGN (observable); |
| 68 | |
| 69 | /* Attach F as an observer to this observable. F cannot be |
| 70 | detached. */ |
| 71 | void attach (const func_type &f) |
| 72 | { |
| 73 | m_observers.emplace_back (nullptr, f); |
| 74 | } |
| 75 | |
| 76 | /* Attach F as an observer to this observable. T is a reference to |
| 77 | a token that can be used to later remove F. */ |
| 78 | void attach (const func_type &f, const token &t) |
| 79 | { |
| 80 | m_observers.emplace_back (&t, f); |
| 81 | } |
| 82 | |
| 83 | /* Remove observers associated with T from this observable. T is |
| 84 | the token that was previously passed to any number of "attach" |
| 85 | calls. */ |
| 86 | void detach (const token &t) |
| 87 | { |
| 88 | auto iter = std::remove_if (m_observers.begin (), |
| 89 | m_observers.end (), |
| 90 | [&] (const std::pair<const token *, |
| 91 | func_type> &e) |
| 92 | { |
| 93 | return e.first == &t; |
| 94 | }); |
| 95 | |
| 96 | m_observers.erase (iter, m_observers.end ()); |
| 97 | } |
| 98 | |
| 99 | /* Notify all observers that are attached to this observable. */ |
| 100 | void notify (T... args) const |
| 101 | { |
| 102 | if (observer_debug) |
| 103 | fprintf_unfiltered (gdb_stdlog, "observable %s notify() called\n", |
| 104 | m_name); |
| 105 | for (auto &&e : m_observers) |
| 106 | e.second (args...); |
| 107 | } |
| 108 | |
| 109 | private: |
| 110 | |
| 111 | std::vector<std::pair<const token *, func_type>> m_observers; |
| 112 | const char *m_name; |
| 113 | }; |
| 114 | |
| 115 | } /* namespace observers */ |
| 116 | |
| 117 | } /* namespace gdb */ |
| 118 | |
| 119 | #endif /* COMMON_OBSERVABLE_H */ |