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1 office 1 /**
2 * @file BPredicate.h
3 * @author Ambroz Bizjak <ambrop7@gmail.com>
4 *
5 * @section LICENSE
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions are met:
9 * 1. Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 * notice, this list of conditions and the following disclaimer in the
13 * documentation and/or other materials provided with the distribution.
14 * 3. Neither the name of the author nor the
15 * names of its contributors may be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
20 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
21 * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
22 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
23 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
25 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
27 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 *
29 * @section DESCRIPTION
30 *
31 * Object that parses and evaluates a logical expression.
32 * Allows the user to define custom functions than can be
33 * used in the expression.
34 *
35 * Syntax and semantics for logical expressions:
36 *
37 * - true
38 * Logical true constant. Evaluates to 1.
39 *
40 * - false
41 * Logical false constant. Evaluates to 0.
42 *
43 * - NOT expression
44 * Logical negation. If the expression evaluates to error, the
45 * negation evaluates to error.
46 *
47 * - expression OR expression
48 * Logical disjunction. The second expression is only evaluated
49 * if the first expression evaluates to false. If a sub-expression
50 * evaluates to error, the disjunction evaluates to error.
51 *
52 * - expression AND expression
53 * Logical conjunction. The second expression is only evaluated
54 * if the first expression evaluates to true. If a sub-expression
55 * evaluates to error, the conjunction evaluates to error.
56 *
57 * - function(arg, ..., arg)
58 * Evaluation of a user-provided function (function is the name of the
59 * function, [a-zA-Z0-9_]+).
60 * If the function with the given name does not exist, it evaluates to
61 * error.
62 * Arguments are evaluated from left to right. Each argument can either
63 * be a logical expression or a string (characters enclosed in double
64 * quotes, without any double quote).
65 * If an argument is encountered, but all needed arguments have already
66 * been evaluated, the function evaluates to error.
67 * If an argument is of wrong type, it is not evaluated and the function
68 * evaluates to error.
69 * If an argument evaluates to error, the function evaluates to error.
70 * If after all arguments have been evaluated, the function needs more
71 * arguments, it evaluates to error.
72 * Then the handler function is called. If it returns anything other
73 * than 1 and 0, the function evaluates to error. Otherwise it evaluates
74 * to what the handler function returned.
75 */
76  
77 #ifndef BADVPN_PREDICATE_BPREDICATE_H
78 #define BADVPN_PREDICATE_BPREDICATE_H
79  
80 #include <misc/debug.h>
81 #include <structure/BAVL.h>
82 #include <base/DebugObject.h>
83  
84 #define PREDICATE_TYPE_BOOL 1
85 #define PREDICATE_TYPE_STRING 2
86  
87 #define PREDICATE_MAX_NAME 16
88 #define PREDICATE_MAX_ARGS 16
89  
90 /**
91 * Handler function called when evaluating a custom function in the predicate.
92 *
93 * @param user value passed to {@link BPredicateFunction_Init}
94 * @param args arguments to the function. Points to an array of pointers (as many as the
95 * function has arguments), where each pointer points to either to an int or
96 * a zero-terminated string (depending on the type of the argument).
97 * @return 1 for true, 0 for false, -1 for error
98 */
99 typedef int (*BPredicate_callback) (void *user, void **args);
100  
101 /**
102 * Object that parses and evaluates a logical expression.
103 * Allows the user to define custom functions than can be
104 * used in the expression.
105 */
106 typedef struct {
107 DebugObject d_obj;
108 void *root;
109 BAVL functions_tree;
110 #ifndef NDEBUG
111 int in_function;
112 #endif
113 } BPredicate;
114  
115 /**
116 * Object that represents a custom function in {@link BPredicate}.
117 */
118 typedef struct {
119 DebugObject d_obj;
120 BPredicate *p;
121 char name[PREDICATE_MAX_NAME + 1];
122 int args[PREDICATE_MAX_ARGS];
123 int num_args;
124 BPredicate_callback callback;
125 void *user;
126 BAVLNode tree_node;
127 } BPredicateFunction;
128  
129 /**
130 * Initializes the object.
131 *
132 * @param p the object
133 * @param str logical expression
134 * @return 1 on success, 0 on failure
135 */
136 int BPredicate_Init (BPredicate *p, char *str) WARN_UNUSED;
137  
138 /**
139 * Frees the object.
140 * Must have no custom functions.
141 * Must not be called from function handlers.
142 *
143 * @param p the object
144 */
145 void BPredicate_Free (BPredicate *p);
146  
147 /**
148 * Evaluates the logical expression.
149 * Must not be called from function handlers.
150 *
151 * @param p the object
152 * @return 1 for true, 0 for false, -1 for error
153 */
154 int BPredicate_Eval (BPredicate *p);
155  
156 /**
157 * Registers a custom function for {@link BPredicate}.
158 * Must not be called from function handlers.
159 *
160 * @param o the object
161 * @param p predicate to register the function for
162 * @param args array of argument types. Each type is either PREDICATE_TYPE_BOOL or PREDICATE_TYPE_STRING.
163 * @param num_args number of arguments for the function. Must be >=0 and <=PREDICATE_MAX_ARGS.
164 * @param callback handler to call to evaluate the function
165 * @param user value to pass to handler
166 */
167 void BPredicateFunction_Init (BPredicateFunction *o, BPredicate *p, char *name, int *args, int num_args, BPredicate_callback callback, void *user);
168  
169 /**
170 * Removes a custom function for {@link BPredicate}.
171 * Must not be called from function handlers.
172 *
173 * @param o the object
174 */
175 void BPredicateFunction_Free (BPredicateFunction *o);
176  
177 #endif