BadVPN – Blame information for rev 1
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1 | office | 1 | /** |
2 | * @file dead.h |
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3 | * @author Ambroz Bizjak <ambrop7@gmail.com> |
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4 | * |
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5 | * @section LICENSE |
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6 | * |
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7 | * Redistribution and use in source and binary forms, with or without |
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8 | * modification, are permitted provided that the following conditions are met: |
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9 | * 1. Redistributions of source code must retain the above copyright |
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10 | * notice, this list of conditions and the following disclaimer. |
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11 | * 2. Redistributions in binary form must reproduce the above copyright |
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12 | * notice, this list of conditions and the following disclaimer in the |
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13 | * documentation and/or other materials provided with the distribution. |
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14 | * 3. Neither the name of the author nor the |
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15 | * names of its contributors may be used to endorse or promote products |
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16 | * derived from this software without specific prior written permission. |
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17 | * |
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18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND |
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19 | * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED |
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20 | * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE |
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21 | * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
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22 | * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
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23 | * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
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24 | * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND |
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25 | * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
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26 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
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27 | * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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28 | * |
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29 | * @section DESCRIPTION |
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30 | * |
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31 | * Dead mechanism definitions. |
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32 | * |
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33 | * The dead mechanism is a way for a piece of code to detect whether some |
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34 | * specific event has occured during some operation (usually during calling |
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35 | * a user-provided handler function), without requiring access to memory |
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36 | * that might no longer be available because of the event. |
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37 | * |
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38 | * It works somehow like that: |
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39 | * |
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40 | * First a dead variable ({@link dead_t}) is allocated somewhere, and |
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41 | * initialized with {@link DEAD_INIT}, e.g.: |
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42 | * DEAD_INIT(dead); |
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43 | * |
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44 | * When the event that needs to be caught occurs, {@link DEAD_KILL} is |
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45 | * called, e.g.: |
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46 | * DEAD_KILL(dead); |
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47 | * The memory used by the dead variable is no longer needed after |
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48 | * that. |
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49 | * |
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50 | * If a piece of code needs to know whether the event occured during some |
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51 | * operation (but it must not have occured before!), it puts {@link DEAD_ENTER}} |
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52 | * in front of the operation, and does {@link DEAD_LEAVE} at the end. If |
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53 | * {@link DEAD_LEAVE} returned nonzero, the event occured, otherwise it did |
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54 | * not. Example: |
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55 | * DEAD_ENTER(dead) |
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56 | * HandlerFunction(); |
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57 | * if (DEAD_LEAVE(dead)) { |
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58 | * (event occured) |
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59 | * } |
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60 | * |
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61 | * If is is needed to check for the event more than once in a single block, |
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62 | * {@link DEAD_DECLARE} should be put somewhere before, and {@link DEAD_ENTER2} |
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63 | * should be used instead of {@link DEAD_ENTER}. |
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64 | * |
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65 | * If it is needed to check for multiple events (dead variables) at the same |
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66 | * time, DEAD_*_N macros should be used instead, specifying different |
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67 | * identiers as the first argument for different dead variables. |
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68 | */ |
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69 | |||
70 | #ifndef BADVPN_MISC_DEAD_H |
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71 | #define BADVPN_MISC_DEAD_H |
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72 | |||
73 | #include <stdlib.h> |
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74 | |||
75 | /** |
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76 | * Dead variable. |
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77 | */ |
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78 | typedef int *dead_t; |
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79 | |||
80 | /** |
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81 | * Initializes a dead variable. |
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82 | */ |
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83 | #define DEAD_INIT(ptr) { ptr = NULL; } |
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84 | |||
85 | /** |
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86 | * Kills the dead variable, |
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87 | */ |
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88 | #define DEAD_KILL(ptr) { if (ptr) *(ptr) = 1; } |
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89 | |||
90 | /** |
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91 | * Kills the dead variable with the given value, or does nothing |
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92 | * if the value is 0. The value will seen by {@link DEAD_KILLED}. |
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93 | */ |
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94 | #define DEAD_KILL_WITH(ptr, val) { if (ptr) *(ptr) = (val); } |
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95 | |||
96 | /** |
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97 | * Declares dead catching variables. |
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98 | */ |
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99 | #define DEAD_DECLARE int badvpn__dead; dead_t badvpn__prev_ptr; |
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100 | |||
101 | /** |
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102 | * Enters a dead catching using already declared dead catching variables. |
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103 | * The dead variable must have been initialized with {@link DEAD_INIT}, |
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104 | * and {@link DEAD_KILL} must not have been called yet. |
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105 | * {@link DEAD_LEAVE2} must be called before the current scope is left. |
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106 | */ |
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107 | #define DEAD_ENTER2(ptr) { badvpn__dead = 0; badvpn__prev_ptr = ptr; ptr = &badvpn__dead; } |
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108 | |||
109 | /** |
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110 | * Declares dead catching variables and enters a dead catching. |
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111 | * The dead variable must have been initialized with {@link DEAD_INIT}, |
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112 | * and {@link DEAD_KILL} must not have been called yet. |
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113 | * {@link DEAD_LEAVE2} must be called before the current scope is left. |
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114 | */ |
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115 | #define DEAD_ENTER(ptr) DEAD_DECLARE DEAD_ENTER2(ptr) |
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116 | |||
117 | /** |
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118 | * Leaves a dead catching. |
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119 | */ |
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120 | #define DEAD_LEAVE2(ptr) { if (!badvpn__dead) ptr = badvpn__prev_ptr; if (badvpn__prev_ptr) *badvpn__prev_ptr = badvpn__dead; } |
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121 | |||
122 | /** |
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123 | * Returns 1 if {@link DEAD_KILL} was called for the dead variable, 0 otherwise. |
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124 | * Must be called after entering a dead catching. |
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125 | */ |
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126 | #define DEAD_KILLED (badvpn__dead) |
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127 | |||
128 | #define DEAD_DECLARE_N(n) int badvpn__dead##n; dead_t badvpn__prev_ptr##n; |
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129 | #define DEAD_ENTER2_N(n, ptr) { badvpn__dead##n = 0; badvpn__prev_ptr##n = ptr; ptr = &badvpn__dead##n;} |
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130 | #define DEAD_ENTER_N(n, ptr) DEAD_DECLARE_N(n) DEAD_ENTER2_N(n, ptr) |
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131 | #define DEAD_LEAVE2_N(n, ptr) { if (!badvpn__dead##n) ptr = badvpn__prev_ptr##n; if (badvpn__prev_ptr##n) *badvpn__prev_ptr##n = badvpn__dead##n; } |
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132 | #define DEAD_KILLED_N(n) (badvpn__dead##n) |
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133 | |||
134 | #endif |