[age restriction] progress 10/n

More work towards support for extensions:
- Prepared statements and DB-plugin-functions for setting and retrieving
  configurations from the database added.
- primitive "registry" of extensions for age restrictions and peer2peer
  (stub)
- TALER_Extensions now with FP for parsing, setting and converting a
  configuration.
- /management/extensions handler now verifies signature of the (opaque)
  json object for all extensions.
- /management/extensions handler calls the FP in the corrensponding
  TALER_Extension for parsing and setting the configuration of a
  particular extension

More work towards age restriction:
- TALER_Extensions interfaces for config-parser, -setter and converter
  implemented for age restriction
- DB event handler now retrieves config from database, parses it and
  sets it (the age mask) in the global extension.
- load_age_mask now loads age mask from the global extension (and not
  from the config file)
- add age_restricted_denoms to /keys response

1 files changed, 58 insertions, 5 deletions

diff --git a/src/include/taler_extensions.h b/src/include/taler_extensions.h
index b6d5c826c..199776eb7 100644
--- a/src/include/taler_extensions.h
+++ b/src/include/taler_extensions.h
@@ -23,6 +23,7 @@
 
 #include <gnunet/gnunet_util_lib.h>
 #include "taler_crypto_lib.h"
+#include "taler_json_lib.h"
 
 
 #define TALER_EXTENSION_SECTION_PREFIX "exchange-extension-"
@@ -39,22 +40,42 @@ enum TALER_Extension_Type
 {
   TALER_Extension_AgeRestriction = 0,
   TALER_Extension_Peer2Peer = 1,
-  TALER_Extension_Max = 2
+  TALER_Extension_Max = 2 // Must be last
 };
 
+/*
+ * TODO oec: documentation
+ */
 struct TALER_Extension
 {
   enum TALER_Extension_Type type;
   char *name;
   bool critical;
   void *config;
+
+  enum GNUNET_GenericReturnValue (*test_config)(const json_t *config);
+  enum GNUNET_GenericReturnValue (*parse_and_set_config)(struct
+                                                         TALER_Extension *this,
+                                                         const json_t *config);
+  json_t *(*config_to_json)(const struct TALER_Extension *this);
 };
 
-/*
- * TALER Peer2Peer Extension
- * FIXME oec
+/**
+ * Generic functions for extensions
  */
 
+/**
+ * Finds and returns a supported extension by a given name.
+ *
+ * @param name name of the extension to lookup
+ * @param extensions list of TALER_Extensions as haystack, terminated by an entry of type TALER_Extension_Max
+ * @param[out] ext set to the extension, if found, NULL otherwise
+ * @return GNUNET_OK if extension was found, GNUNET_NO otherwise
+ */
+enum GNUNET_GenericReturnValue
+TALER_extension_get_by_name (const char *name,
+                             const struct TALER_Extension **extensions,
+                             const struct TALER_Extension **ext);
 
 /*
  * TALER Age Restriction Extension
@@ -72,7 +93,19 @@ struct TALER_Extension
                                                 << 21)
 
 /**
- * @param groups String representation of age groups, like: "8:10:12:14:16:18:21"
+ * @brief Parses a string as a list of age groups.
+ *
+ * The string must consist of a colon-separated list of increasing integers
+ * between 0 and 31.  Each entry represents the beginning of a new age group.
+ * F.e. the string "8:10:12:14:16:18:21" parses into the following list of age
+ * groups
+ *   0-7, 8-9, 10-11, 12-13, 14-15, 16-17, 18-20, 21-...
+ * which then is represented as bit mask with the corresponding bits set:
+ *   31     24        16        8         0
+ *   |      |         |         |         |
+ *   oooooooo  oo1oo1o1  o1o1o1o1  ooooooo1
+ *
+ * @param groups String representation of age groups
  * @param[out] mask Mask representation for age restriction.
  * @return Error, if age groups were invalid, OK otherwise.
  */
@@ -81,6 +114,19 @@ TALER_parse_age_group_string (char *groups,
                               struct TALER_AgeMask *mask);
 
 /**
+ * Encodes the age mask into a string, like "8:10:12:14:16:18:21"
+ *
+ * @param mask Age mask
+ * @return String representation of the age mask, allocated by GNUNET_malloc.
+ *         Can be used as value in the TALER config.
+ */
+char *
+TALER_age_mask_to_string (const struct TALER_AgeMask *mask);
+
+
+/**
+ * @brief Reads the age groups from the configuration and sets the
+ * corresponding age mask.
  *
  * @param cfg
  * @param[out] mask for age restriction, will be set to 0 if age restriction is disabled.
@@ -90,4 +136,11 @@ TALER_parse_age_group_string (char *groups,
 enum TALER_Extension_ReturnValue
 TALER_get_age_mask (const struct GNUNET_CONFIGURATION_Handle *cfg,
                     struct TALER_AgeMask *mask);
+
+
+/*
+ * TALER Peer2Peer Extension
+ * TODO oec
+ */
+
 #endif