Add automatically compiled PCRE2_REGEX config parameter type

The regex strings are compiled automatically. During file parsing,
the string is compiled once using default settings to check that
the pattern is valid. Once a module asks for the compiled pcre2_code,
the pattern is compiled again with module given settings.

The regex string in the config file should be enclosed within '/ ... /'

include/maxscale/config.h

@@ -24,6 +24,7 @@
 
 #include <maxscale/modinfo.h>
 #include <maxscale/jansson.h>
+#include <maxscale/pcre2.h>
 
 MXS_BEGIN_DECLS
 
@@ -352,12 +353,40 @@ struct server* config_get_server(const MXS_CONFIG_PARAMETER *params, const char
 int config_get_server_list(const MXS_CONFIG_PARAMETER *params, const char *key,
                            struct server*** output);
 
+/**
+ * Get a compiled regular expression. The returned @c pcre2_code should be freed
+ * by the caller.
+ *
+ * @param params List of configuration parameters
+ * @param key Parameter name
+ * @param options PCRE2 compilation options
+ * @return The compiled PCRE2 code, or NULL on error
+ */
+pcre2_code* config_get_compiled_regex(const MXS_CONFIG_PARAMETER *params, const char *key,
+                                      uint32_t options);
+
+/**
+ * Get a compiled regular expression and the capture count of the pattern. The
+ * @c pcre2_code should be freed by the caller.
+ *
+ * @param params List of configuration parameters
+ * @param key Parameter name
+ * @param options PCRE2 compilation options
+ * @param output_code Output for compilation result
+ * @param output_capcount Output for capture count
+ * @return True on success, false otherwise
+ */
+bool config_get_compiled_regex_capcount(const MXS_CONFIG_PARAMETER *params,
+                                        const char *key, uint32_t options,
+                                        pcre2_code** output_code,
+                                        uint32_t* output_capcount);
+
 /**
  * Parse a list of server names and write the results in an array of strings
  * with one server name in each. The output array and its elements should be
  * deallocated by the caller. The server names are not checked to be actual
  * configured servers.
- * 
+ *
  * The output array may contain more elements than the the value returned, but these
  * extra elements are null and in the end of the array. If no server names were
  * parsed or if an error occurs, nothing is written to the output parameter.

include/maxscale/modinfo.h

@@ -84,7 +84,8 @@ enum mxs_module_param_type
     MXS_MODULE_PARAM_PATH, /**< Path to a file or a directory */
     MXS_MODULE_PARAM_SERVICE, /**< Service name */
     MXS_MODULE_PARAM_SERVER, /**< Server name */
-    MXS_MODULE_PARAM_SERVERLIST /**< List of server names, separated by ',' */
+    MXS_MODULE_PARAM_SERVERLIST, /**< List of server names, separated by ',' */
+    MXS_MODULE_PARAM_REGEX /**< A regex string enclosed in '/' */
 };
 
 /** Maximum and minimum values for integer types */
@@ -246,6 +247,8 @@ static inline const char* mxs_module_param_type_to_string(enum mxs_module_param_
         return "server";
     case MXS_MODULE_PARAM_SERVERLIST:
         return "serverlist";
+    case MXS_MODULE_PARAM_REGEX:
+        return "regular expression";
     default:
         ss_dassert(!true);
         return "unknown";