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/* expr.c - an expression class.
* This module contains all code needed to represent expressions. Most
* importantly, that means code to parse and execute them. Expressions
* heavily depend on (loadable) functions, so it works in conjunction
* with the function manager.
*
* Module begun 2007-11-30 by Rainer Gerhards
*
* Copyright 2007 Rainer Gerhards and Adiscon GmbH.
*
* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
* W A R N I N G
*
* This module is not really existing. The current code has never been
* tested or run. It is just some preparation for when we actually implement
* this fuctionality!
*
* !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
*
* This file is part of rsyslog.
*
* Rsyslog 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, either version 3 of the License, or
* (at your option) any later version.
*
* Rsyslog 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. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Rsyslog. If not, see <http://www.gnu.org/licenses/>.
*
* A copy of the GPL can be found in the file "COPYING" in this distribution.
*/
#include "config.h"
#include <assert.h>
#include "rsyslog.h"
#include "template.h"
#include "stringbuf.h"
/* This is the syntax of an expression. I keep it as inline documentation
* as this enhances the chance that it is updates should there be a change.
*
* expr = (simple-string / template-string / function / property) [* expr ]
* simple-string = "'" chars "'"
* template-string = '"' template-as--1.19.11-and-below '"'
* ; string as used in previous $template directive
* function = function-name "(" expr ")"
* property = [list of property names]
*/
/* a single expression node */
typedef struct exprNode_s {
} exprNode_t;
/* the expression object */
typedef struct expr_s {
exprNode_t enodeRoot; /* the root node where evaluation starts */
/* a variant (or such) to hold the ultimate return value */
/* for the time being, we just use a string. That still provides us the
* hooks for doing better later.
*/
rsCStrObj *cstrConst;
} expr_t;
/* the following three need to be implemented, I just provide some dummies for
* now -- rgerhards, 2008-02-13
*/
static rsRetVal exprConstruct() { return RS_RET_OK; }
static rsRetVal exprFinalize() { return RS_RET_OK; }
static rsRetVal exprDestruct() { return RS_RET_OK; }
//exprDestruct MUST free the cstrConst!
/* evaluate an expression and store the result. pMsg is optional, but if
* it is not given, no message-based variables can be accessed. The expression
* must previously have been created.
* rgerhards, 2008-02-09
*/
rsRetVal
exprEval(expr_t *pThis, msg_t *pMsg)
{
DEFiRet;
//ISOBJ_TYPE_assert(pThis, expr);
RETiRet;
}
/* returns the expression result as a string. The string is read-only and valid
* only as long as the expression exists and is not newly evaluated. If the caller
* needs to access it for an extended period of time, it must copy it. This is a
* performance optimization, as most expression results are expected to be used
* only for a brief period. In such cases, it saves us the need to copy the string.
* Also, it is assumed that most callers will hold their private expression. If it
* is not shared, the caller can count on the string to remain stable as long as it
* does not reevaluate the expression (via exprEval or other means) or destruct it.
* rgerhards, 2008-02-09
*/
rsRetVal
exprGetStr(expr_t *pThis, rsCStrObj **ppStr)
{
DEFiRet;
//ISOBJ_TYPE_assert(pThis, expr);
ASSERT(ppStr != NULL);
RETiRet;
}
/* parse an expression from a string. The string MUST include the full expression. The
* expression object is only created if there is no error during parsing.
* The string is a standard C string. It must NOT contain anything else but the
* expression. Most importantly, it must not contain any comments after the
* expression.
* rgerhards, 2008-02-09 (a rainy tenerife return flight day ;))
*/
rsRetVal
exprParseStr(expr_t **ppThis, uchar *p)
{
DEFiRet;
expr_t *pThis = NULL;
ASSERT(ppThis != NULL);
ASSERT(p != NULL);
CHKiRet(exprConstruct(&pThis));
// TODO: use this method, but requires changing stringbuf.c: CHKiRet(rsCStrConstruct(&pThis->cstrConst));
if((pThis->cstrConst = rsCStrConstruct()) == NULL) {
ABORT_FINALIZE(RS_RET_OUT_OF_MEMORY);
}
/* so far, we are a dummy - we just pull the first string and
* ignore the rest...
*/
while(*p && *p != '"')
++p; /* find begin of string */
if(*p == '"')
++p; /* eat it */
/* we got it, now copy over everything up until the end of the string */
while(*p && *p != '"') {
CHKiRet(rsCStrAppendChar(pThis->cstrConst, *p));
++p;
}
/* we are done with it... */
CHKiRet(rsCStrFinish(pThis->cstrConst));
CHKiRet(exprFinalize(&pThis));
/* we are successfully done, so store the result */
*ppThis = pThis;
finalize_it:
if(iRet != RS_RET_OK) {
if(pThis != NULL)
exprDestruct(pThis);
}
RETiRet;
}
/* vi:set ai:
*/
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