178 lines
6.3 KiB
C
178 lines
6.3 KiB
C
/**
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* @file BPredicate.h
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* @author Ambroz Bizjak <ambrop7@gmail.com>
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*
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* @section LICENSE
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* @section DESCRIPTION
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*
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* Object that parses and evaluates a logical expression.
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* Allows the user to define custom functions than can be
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* used in the expression.
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*
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* Syntax and semantics for logical expressions:
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*
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* - true
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* Logical true constant. Evaluates to 1.
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*
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* - false
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* Logical false constant. Evaluates to 0.
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*
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* - NOT expression
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* Logical negation. If the expression evaluates to error, the
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* negation evaluates to error.
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*
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* - expression OR expression
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* Logical disjunction. The second expression is only evaluated
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* if the first expression evaluates to false. If a sub-expression
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* evaluates to error, the disjunction evaluates to error.
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*
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* - expression AND expression
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* Logical conjunction. The second expression is only evaluated
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* if the first expression evaluates to true. If a sub-expression
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* evaluates to error, the conjunction evaluates to error.
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*
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* - function(arg, ..., arg)
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* Evaluation of a user-provided function (function is the name of the
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* function, [a-zA-Z0-9_]+).
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* If the function with the given name does not exist, it evaluates to
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* error.
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* Arguments are evaluated from left to right. Each argument can either
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* be a logical expression or a string (characters enclosed in double
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* quotes, without any double quote).
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* If an argument is encountered, but all needed arguments have already
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* been evaluated, the function evaluates to error.
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* If an argument is of wrong type, it is not evaluated and the function
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* evaluates to error.
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* If an argument evaluates to error, the function evaluates to error.
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* If after all arguments have been evaluated, the function needs more
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* arguments, it evaluates to error.
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* Then the handler function is called. If it returns anything other
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* than 1 and 0, the function evaluates to error. Otherwise it evaluates
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* to what the handler function returned.
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*/
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#ifndef BADVPN_PREDICATE_BPREDICATE_H
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#define BADVPN_PREDICATE_BPREDICATE_H
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#include <misc/debug.h>
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#include <structure/BAVL.h>
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#include <base/DebugObject.h>
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#define PREDICATE_TYPE_BOOL 1
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#define PREDICATE_TYPE_STRING 2
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#define PREDICATE_MAX_NAME 16
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#define PREDICATE_MAX_ARGS 16
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/**
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* Handler function called when evaluating a custom function in the predicate.
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*
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* @param user value passed to {@link BPredicateFunction_Init}
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* @param args arguments to the function. Points to an array of pointers (as many as the
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* function has arguments), where each pointer points to either to an int or
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* a zero-terminated string (depending on the type of the argument).
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* @return 1 for true, 0 for false, -1 for error
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*/
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typedef int (*BPredicate_callback) (void *user, void **args);
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/**
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* Object that parses and evaluates a logical expression.
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* Allows the user to define custom functions than can be
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* used in the expression.
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*/
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typedef struct {
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DebugObject d_obj;
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void *root;
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BAVL functions_tree;
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#ifndef NDEBUG
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int in_function;
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#endif
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} BPredicate;
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/**
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* Object that represents a custom function in {@link BPredicate}.
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*/
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typedef struct {
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DebugObject d_obj;
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BPredicate *p;
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char name[PREDICATE_MAX_NAME + 1];
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int args[PREDICATE_MAX_ARGS];
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int num_args;
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BPredicate_callback callback;
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void *user;
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BAVLNode tree_node;
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} BPredicateFunction;
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/**
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* Initializes the object.
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*
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* @param p the object
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* @param str logical expression
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* @return 1 on success, 0 on failure
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*/
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int BPredicate_Init (BPredicate *p, char *str) WARN_UNUSED;
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/**
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* Frees the object.
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* Must have no custom functions.
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* Must not be called from function handlers.
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*
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* @param p the object
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*/
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void BPredicate_Free (BPredicate *p);
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/**
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* Evaluates the logical expression.
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* Must not be called from function handlers.
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*
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* @param p the object
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* @return 1 for true, 0 for false, -1 for error
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*/
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int BPredicate_Eval (BPredicate *p);
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/**
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* Registers a custom function for {@link BPredicate}.
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* Must not be called from function handlers.
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*
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* @param o the object
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* @param p predicate to register the function for
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* @param args array of argument types. Each type is either PREDICATE_TYPE_BOOL or PREDICATE_TYPE_STRING.
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* @param num_args number of arguments for the function. Must be >=0 and <=PREDICATE_MAX_ARGS.
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* @param callback handler to call to evaluate the function
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* @param user value to pass to handler
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*/
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void BPredicateFunction_Init (BPredicateFunction *o, BPredicate *p, char *name, int *args, int num_args, BPredicate_callback callback, void *user);
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/**
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* Removes a custom function for {@link BPredicate}.
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* Must not be called from function handlers.
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*
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* @param o the object
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*/
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void BPredicateFunction_Free (BPredicateFunction *o);
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#endif
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