OpenTTD Source  12.0-beta2
backup_type.hpp
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1 /*
2  * This file is part of OpenTTD.
3  * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
4  * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
5  * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
6  */
7 
10 #ifndef BACKUP_TYPE_HPP
11 #define BACKUP_TYPE_HPP
12 
13 #include "../debug.h"
14 
20 template <typename T>
21 struct Backup {
28  Backup(T &original, const char * const file, const int line) : original(original), valid(true), original_value(original), file(file), line(line) {}
29 
37  template <typename U>
38  Backup(T &original, const U &new_value, const char * const file, const int line) : original(original), valid(true), original_value(original), file(file), line(line)
39  {
40  /* Note: We use a separate typename U, so type conversions are handled by assignment operator. */
41  original = new_value;
42  }
43 
48  {
49  /* Check whether restoration was done */
50  if (this->valid)
51  {
52  /* We cannot assert here, as missing restoration is 'normal' when exceptions are thrown.
53  * Exceptions are especially used to abort world generation. */
54  Debug(misc, 0, "{}:{}: Backed-up value was not restored!", this->file, this->line);
55  this->Restore();
56  }
57  }
58 
63  bool IsValid() const
64  {
65  return this->valid;
66  }
67 
72  const T &GetOriginalValue() const
73  {
74  assert(this->valid);
75  return original_value;
76  }
77 
83  template <typename U>
84  void Change(const U &new_value)
85  {
86  /* Note: We use a separate typename U, so type conversions are handled by assignment operator. */
87  assert(this->valid);
88  original = new_value;
89  }
90 
94  void Revert()
95  {
96  assert(this->valid);
97  this->original = this->original_value;
98  }
99 
103  void Trash()
104  {
105  assert(this->valid);
106  this->valid = false;
107  }
108 
112  void Restore()
113  {
114  this->Revert();
115  this->Trash();
116  }
117 
122  void Update()
123  {
124  assert(this->valid);
125  this->original_value = this->original;
126  }
127 
132  bool Verify() const
133  {
134  assert(this->valid);
135  return this->original_value == this->original;
136  }
137 
138 private:
139  T &original;
140  bool valid;
141  T original_value;
142 
143  const char * const file;
144  const int line;
145 };
146 
147 #endif /* BACKUP_TYPE_HPP */
Backup::Change
void Change(const U &new_value)
Change the value of the variable.
Definition: backup_type.hpp:84
Backup
Class to backup a specific variable and restore it later.
Definition: backup_type.hpp:21
Backup::Verify
bool Verify() const
Check whether the variable is currently equals the backup.
Definition: backup_type.hpp:132
Backup::Backup
Backup(T &original, const char *const file, const int line)
Backup variable.
Definition: backup_type.hpp:28
Backup::Backup
Backup(T &original, const U &new_value, const char *const file, const int line)
Backup variable and switch to new value.
Definition: backup_type.hpp:38
Backup::~Backup
~Backup()
Check whether the variable was restored on object destruction.
Definition: backup_type.hpp:47
Backup::Update
void Update()
Update the backup.
Definition: backup_type.hpp:122
Backup::IsValid
bool IsValid() const
Checks whether the variable was already restored.
Definition: backup_type.hpp:63
Backup::Trash
void Trash()
Trash the backup.
Definition: backup_type.hpp:103
Backup::Restore
void Restore()
Restore the variable.
Definition: backup_type.hpp:112
Backup::GetOriginalValue
const T & GetOriginalValue() const
Returns the backupped value.
Definition: backup_type.hpp:72
Debug
#define Debug(name, level, format_string,...)
Ouptut a line of debugging information.
Definition: debug.h:37
Backup::Revert
void Revert()
Revert the variable to its original value, but do not mark it as restored.
Definition: backup_type.hpp:94