X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/disorder/blobdiff_plain/52b88d2428a808d0636a1cb8205a1f891fc23e6a..b0b15b7ced28b3c6ddfcd4b0a7e46ee6432a243c:/lib/eclient.h

diff --git a/lib/eclient.h b/lib/eclient.h
index 157ad59..86caf75 100644
--- a/lib/eclient.h
+++ b/lib/eclient.h
@@ -42,9 +42,13 @@ struct queue_entry;
  * These must all be valid.
  */
 typedef struct disorder_eclient_callbacks {
-  /** @brief Called when a communication error (e.g. connected refused) occurs.
+  /** @brief Called when a communication error occurs.
    * @param u from disorder_eclient_new()
    * @param msg error message
+   *
+   * This might be called at any time, and indicates a low-level error,
+   * e.g. connection refused by the server.  It does not mean that any requests
+   * made of the owning eclient will not be fulfilled at some point.
    */
   void (*comms_error)(void *u, const char *msg);
   
@@ -52,6 +56,11 @@ typedef struct disorder_eclient_callbacks {
    * @param u from disorder_eclient_new()
    * @param v from failed command, or NULL if during setup
    * @param msg error message
+   *
+   * This call is obsolete at least in its current form, in which it is used to
+   * report most errors from most requests.  Ultimately requests-specific
+   * errors will be reported in a request-specific way rather than via this
+   * generic callback.
    */
   void (*protocol_error)(void *u, void *v, int code, const char *msg);
 
@@ -135,32 +144,89 @@ struct kvp;
 struct sink;
 
 /* Completion callbacks.  These provide the result of operations to the caller.
- * It is always allowed for these to be null pointers if you don't care about
- * the result. */
+ * Unlike in earlier releases, these are not allowed to be NULL. */
 
-typedef void disorder_eclient_no_response(void *v);
-/* completion callback with no data */
+/** @brief Trivial completion callback
+ * @param v User data
+ * @param error Error string or NULL on succes
+ */
+typedef void disorder_eclient_no_response(void *v,
+                                          const char *error);
 
 /** @brief String result completion callback
  * @param v User data
- * @param value or NULL
+ * @param error Error string or NULL on succes
+ * @param value Result or NULL
+ *
+ * @p error will be NULL on success.  In this case @p value will be the result
+ * (which might be NULL for disorder_eclient_get(),
+ * disorder_eclient_get_global() and disorder_eclient_userinfo()).
  *
- * @p value can be NULL for disorder_eclient_get(),
- * disorder_eclient_get_global() and disorder_eclient_userinfo().
+ * @p error will be non-NULL on failure.  In this case @p value is always NULL.
  */
-typedef void disorder_eclient_string_response(void *v, const char *value);
-
-typedef void disorder_eclient_integer_response(void *v, long value);
-/* completion callback with a integer result */
+typedef void disorder_eclient_string_response(void *v,
+                                              const char *error,
+                                              const char *value);
 
-typedef void disorder_eclient_volume_response(void *v, int l, int r);
-/* completion callback with a pair of integer results */
+/** @brief String result completion callback
+ * @param v User data
+ * @param error Error string or NULL on succes
+ * @param value Result or 0
+ *
+ * @p error will be NULL on success.  In this case @p value will be the result.
+ *
+ * @p error will be non-NULL on failure.  In this case @p value is always 0.
+ */
+typedef void disorder_eclient_integer_response(void *v,
+                                               const char *error,
+                                               long value);
+/** @brief Volume completion callback
+ * @param v User data
+ * @param error Error string or NULL on success
+ * @param l Left channel volume
+ * @param r Right channel volume
+ *
+ * @p error will be NULL on success.  In this case @p l and @p r will be the
+ * result.
+ *
+ * @p error will be non-NULL on failure.  In this case @p l and @p r are always
+ * 0.
+ */
+typedef void disorder_eclient_volume_response(void *v,
+                                              const char *error,
+                                              int l, int r);
 
-typedef void disorder_eclient_queue_response(void *v, struct queue_entry *q);
-/* completion callback for queue/recent listing */
+/** @brief Queue request completion callback
+ * @param v User data
+ * @param error Error string or NULL on success
+ * @param q Head of queue data list
+ *
+ * @p error will be NULL on success.  In this case @p q will be the (head of
+ * the) result.
+ *
+ * @p error will be non-NULL on failure.  In this case @p q may be NULL but
+ * MIGHT also be some subset of the queue.  For consistent behavior it should
+ * be ignored in the error case.
+ */
+typedef void disorder_eclient_queue_response(void *v,
+                                             const char *error,
+                                             struct queue_entry *q);
 
-typedef void disorder_eclient_list_response(void *v, int nvec, char **vec);
-/* completion callback for file listing etc */
+/** @brief List request completion callback
+ * @param v User data
+ * @param error Error string or NULL on success
+ * @param nvec Number of elements in response list
+ * @param vec Pointer to response list
+ *
+ * @p error will be NULL on success.  In this case @p nvec and @p vec will give
+ * the result.
+ *
+ * @p error will be non-NULL on failure.  In this case @p nvec and @p vec will
+ * be 0 and NULL.
+ */
+typedef void disorder_eclient_list_response(void *v,
+                                            const char *error,
+                                            int nvec, char **vec);
 
 disorder_eclient *disorder_eclient_new(const disorder_eclient_callbacks *cb,
                                        void *u);