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