Refactor config.c functions for testing

To test the configuration validation and default value generation, the
functions needed to be refactored to allow parameters to be passed
directly to the function.

include/maxscale/config.h

@@ -209,24 +209,27 @@ SSL_LISTENER *make_ssl_structure(CONFIG_CONTEXT *obj, bool require_cert, int *er
  * the given parameters are compared to the expected ones. This function also
  * does preliminary type checking for various basic values as well as enumerations.
  *
- * @param module Module name
- * @param type Module type
+ * @param params Module parameters
  * @param key Parameter key
  * @param value Parameter value
  * @param context Configuration context or NULL for no context (uses runtime checks)
  *
  * @return True if the configuration parameter is valid
  */
-bool config_param_is_valid(const char *module, const char *type, const char *key,
+bool config_param_is_valid(const MXS_MODULE_PARAM *params, const char *key,
                            const char *value, const CONFIG_CONTEXT *context);
 
 /**
  * @brief Get a boolean value
  *
+ * The existence of the parameter should be checked with config_get_param() before
+ * calling this function to determine whether the return value represents an existing
+ * value or a missing value.
+ *
  * @param params List of configuration parameters
  * @param key Parameter name
  *
- * @return The value as a boolean
+ * @return The value as a boolean or false if none was found
  */
 bool config_get_bool(const CONFIG_PARAMETER *params, const char *key);
 
@@ -238,7 +241,7 @@ bool config_get_bool(const CONFIG_PARAMETER *params, const char *key);
  * @param params List of configuration parameters
  * @param key Parameter name
  *
- * @return The integer value of the parameter
+ * @return The integer value of the parameter or 0 if no parameter was found
  */
 int config_get_integer(const CONFIG_PARAMETER *params, const char *key);
 
@@ -248,7 +251,7 @@ int config_get_integer(const CONFIG_PARAMETER *params, const char *key);
  * @param params List of configuration parameters
  * @param key Parameter name
  *
- * @return The raw string value
+ * @return The raw string value or an empty string if no parameter was found
  */
 const char* config_get_string(const CONFIG_PARAMETER *params, const char *key);
 
@@ -259,9 +262,11 @@ const char* config_get_string(const CONFIG_PARAMETER *params, const char *key);
  * @param key Parameter name
  * @param values All possible enumeration values
  *
- * @return The enumeration value converted to an int
+ * @return The enumeration value converted to an int or -1 if the parameter was not found
  *
- * TODO: Allow multiple enumeration values
+ * @note The enumeration values should not use -1 so that an undefined parameter is
+ * detected. If -1 is used, config_get_param() should be used to detect whether
+ * the parameter exists
  */
 int config_get_enum(const CONFIG_PARAMETER *params, const char *key, const MXS_ENUM_VALUE *values);
 
@@ -271,12 +276,11 @@ int config_get_enum(const CONFIG_PARAMETER *params, const char *key, const MXS_E
  * Adds any default parameters to @c ctx that aren't already in it.
  *
  * @param ctx    Configuration context where the parameters are added
- * @param module Module name
- * @param type   Module type
+ * @param params Module parameters
  *
  * TODO: Move this to a header internal to the MaxScale core
  */
-void config_add_defaults(CONFIG_CONTEXT *ctx, const char *module, const char *type);
+void config_add_defaults(CONFIG_CONTEXT *ctx, const MXS_MODULE_PARAM *params);
 
 char*               config_clean_string_list(const char* str);
 CONFIG_PARAMETER*   config_clone_param(const CONFIG_PARAMETER* param);