as discussed on the -dev list, introduce a macro to simplify the

writing of common constructs like

	chan = !ast_strlen_zero(cdr->channel) ? cdr->channel : "<unknown>";

(or the if/then/else form) into

	chan = S_OR(cdr->channel, "<unknown>");

The name can be changed if we find a better (and not too long) one;
currently, it is S as String, OR as it mimics the behaviour of
the || operator, but applied to strings.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@14747 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/strings.h

@@ -35,6 +35,11 @@ static force_inline int ast_strlen_zero(const char *s)
 	return (!s || (*s == '\0'));
 }
 
+/*! \brief returns the equivalent of logic or for strings:
+ * first one if not empty, otherwise second one.
+ */
+#define S_OR(a, b)	(!ast_strlen_zero(a) ? (a) : (b))
+
 /*!
   \brief Gets a pointer to the first non-whitespace character in a string.
   \param ast_skip_blanks function being used