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diff --git a/property.c b/property.c
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+/* $Id: property.c 840 2007-09-09 12:17:42Z michael $
+ * $URL: https://ssl.bulix.org/svn/lcd4linux/trunk/property.c $
+ *
+ * dynamic properties
+ *
+ * Copyright (C) 2006 Michael Reinelt <michael@reinelt.co.at>
+ * Copyright (C) 2006 The LCD4Linux Team <lcd4linux-devel@users.sourceforge.net>
+ *
+ * This file is part of LCD4Linux.
+ *
+ * LCD4Linux 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 2, or (at your option)
+ * any later version.
+ *
+ * LCD4Linux 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 this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ */
+
+
+/* 
+ * exported functions:
+ *
+ * void property_load (const char *section, const char *name, const char *defval, PROPERTY *prop)
+ *   initializes and loads a property from the config file and pre-compiles it
+ *
+ * void property_free (PROPERTY *prop)
+ *   frees all property allocations
+ *
+ * int property_eval(PROPERTY * prop)
+ *   evaluates a property; returns 1 if value has changed
+ *
+ * double P2N(PROPERTY * prop)
+ *   returns a (already evaluated) property as number
+ *
+ * char *P2S(PROPERTY * prop)
+ *   returns a (already evaluated) property as string
+ *
+ */
+
+
+#include "config.h"
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include "debug.h"
+#include "cfg.h"
+#include "evaluator.h"
+#include "property.h"
+
+#ifdef WITH_DMALLOC
+#include <dmalloc.h>
+#endif
+
+
+void property_load(const char *section, const char *name, const char *defval, PROPERTY * prop)
+{
+    char *expression;
+
+    /* initialize structure */
+    prop->valid = 0;
+    prop->name = NULL;
+    prop->expression = NULL;
+    prop->compiled = NULL;
+    DelResult(&prop->result);
+
+    /* remember the name */
+    prop->name = strdup(name);
+
+    /* load expression from config, but do not evaluate it */
+    expression = cfg_get_raw(section, name, NULL);
+
+    if (expression == NULL) {
+	if (defval != NULL && *defval != '\0')
+	    debug("Notice: using default value <%s> for property '%s.%s'", defval, section, name);
+	prop->expression = (char *) defval;
+    } else {
+	prop->valid = 1;
+	prop->expression = expression;
+    }
+
+    /* pre-compile the expression */
+    Compile(prop->expression, &prop->compiled);
+
+}
+
+
+int property_valid(PROPERTY * prop)
+{
+    return prop->valid;
+}
+
+
+int property_eval(PROPERTY * prop)
+{
+    RESULT old;
+    int update;
+
+    /* this is a bit ugly: we need to remember the old value */
+    old.type = prop->result.type;
+    old.size = prop->result.size;
+    old.number = prop->result.number;
+    old.string = prop->result.string != NULL ? strdup(prop->result.string) : NULL;
+
+    DelResult(&prop->result);
+    Eval(prop->compiled, &prop->result);
+
+    /* check if property value has changed */
+    update = 1;
+    if (prop->result.type & R_NUMBER && old.type & R_NUMBER && prop->result.number == old.number) {
+	update = 0;
+    }
+    if (prop->result.type & R_STRING && old.type & R_STRING && prop->result.size == old.size) {
+	if (prop->result.string == NULL && old.string == NULL) {
+	    update = 0;
+	} else if (prop->result.string != NULL && old.string != NULL && strcmp(prop->result.string, old.string) == 0) {
+	    update = 0;
+	}
+    }
+
+    if (old.string)
+	free(old.string);
+
+    return update;
+}
+
+
+double P2N(PROPERTY * prop)
+{
+    if (prop == NULL) {
+	error("Property: internal error: NULL property");
+	return 0.0;
+    }
+    return R2N(&prop->result);
+}
+
+
+char *P2S(PROPERTY * prop)
+{
+    if (prop == NULL) {
+	error("Property: internal error: NULL property");
+	return NULL;
+    }
+    return R2S(&prop->result);
+}
+
+void property_free(PROPERTY * prop)
+{
+    if (prop->name != NULL) {
+	free(prop->name);
+	prop->name = NULL;
+    }
+
+    if (prop->expression != NULL) {
+	/* do *not* free expression */
+	prop->expression = NULL;
+    }
+
+    if (prop->compiled != NULL) {
+	free(prop->compiled);
+	prop->compiled = NULL;
+    }
+
+    DelResult(&prop->result);
+}