+ const GNUNET_HashCode * key, size_t size,
+ const void *data, unsigned int queue_priority,
+ unsigned int max_queue_size,
+ struct GNUNET_TIME_Relative timeout,
+ GNUNET_DATASTORE_ContinuationWithStatus cont,
+ void *cont_cls);
+
+
+/**
+ * Process a datum that was stored in the datastore.
+ *
+ * @param cls closure
+ * @param key key for the content
+ * @param size number of bytes in data
+ * @param data content stored
+ * @param type type of the content
+ * @param priority priority of the content
+ * @param anonymity anonymity-level for the content
+ * @param expiration expiration time for the content
+ * @param uid unique identifier for the datum;
+ * maybe 0 if no unique identifier is available
+ */
+typedef void (*GNUNET_DATASTORE_DatumProcessor) (void *cls,
+ const GNUNET_HashCode * key,
+ size_t size, const void *data,
+ enum GNUNET_BLOCK_Type type,
+ uint32_t priority,
+ uint32_t anonymity,
+ struct GNUNET_TIME_Absolute
+ expiration, uint64_t uid);
+
+
+/**
+ * Get a result for a particular key from the datastore. The processor
+ * will only be called once.
+ *
+ * @param h handle to the datastore
+ * @param offset offset of the result (modulo num-results); set to
+ * a random 64-bit value initially; then increment by
+ * one each time; detect that all results have been found by uid
+ * being again the first uid ever returned.
+ * @param key maybe NULL (to match all entries)
+ * @param type desired type, 0 for any
+ * @param queue_priority ranking of this request in the priority queue
+ * @param max_queue_size at what queue size should this request be dropped
+ * (if other requests of higher priority are in the queue)
+ * @param timeout how long to wait at most for a response
+ * @param proc function to call on each matching value;
+ * will be called once with a NULL value at the end
+ * @param proc_cls closure for proc
+ * @return NULL if the entry was not queued, otherwise a handle that can be used to
+ * cancel
+ */
+struct GNUNET_DATASTORE_QueueEntry *
+GNUNET_DATASTORE_get_key (struct GNUNET_DATASTORE_Handle *h, uint64_t offset,
+ const GNUNET_HashCode * key,
+ enum GNUNET_BLOCK_Type type,
+ unsigned int queue_priority,
+ unsigned int max_queue_size,
+ struct GNUNET_TIME_Relative timeout,
+ GNUNET_DATASTORE_DatumProcessor proc, void *proc_cls);
+
+
+/**
+ * Get a single zero-anonymity value from the datastore.
+ * Note that some implementations can ignore the 'offset' and
+ * instead return a random zero-anonymity value. In that case,
+ * detecting the wrap-around based on a repeating UID is at best
+ * probabilistic.
+ *
+ * @param h handle to the datastore
+ * @param offset offset of the result (modulo num-results); set to
+ * a random 64-bit value initially; then increment by
+ * one each time; detect that all results have been found by uid
+ * being again the first uid ever returned.
+ * @param queue_priority ranking of this request in the priority queue
+ * @param max_queue_size at what queue size should this request be dropped
+ * (if other requests of higher priority are in the queue)
+ * @param timeout how long to wait at most for a response
+ * @param type allowed type for the operation (never zero)
+ * @param proc function to call on a random value; it
+ * will be called once with a value (if available)
+ * or with NULL if none value exists.
+ * @param proc_cls closure for proc
+ * @return NULL if the entry was not queued, otherwise a handle that can be used to
+ * cancel
+ */
+struct GNUNET_DATASTORE_QueueEntry *
+GNUNET_DATASTORE_get_zero_anonymity (struct GNUNET_DATASTORE_Handle *h,
+ uint64_t offset,
+ unsigned int queue_priority,
+ unsigned int max_queue_size,
+ struct GNUNET_TIME_Relative timeout,
+ enum GNUNET_BLOCK_Type type,
+ GNUNET_DATASTORE_DatumProcessor proc,
+ void *proc_cls);
+
+
+/**
+ * Get a random value from the datastore for content replication.
+ * Returns a single, random value among those with the highest
+ * replication score, lowering positive replication scores by one for
+ * the chosen value (if only content with a replication score exists,
+ * a random value is returned and replication scores are not changed).
+ *
+ * @param h handle to the datastore
+ * @param queue_priority ranking of this request in the priority queue
+ * @param max_queue_size at what queue size should this request be dropped
+ * (if other requests of higher priority are in the queue)
+ * @param timeout how long to wait at most for a response
+ * @param proc function to call on a random value; it
+ * will be called once with a value (if available)
+ * and always once with a value of NULL.
+ * @param proc_cls closure for proc
+ * @return NULL if the entry was not queued, otherwise a handle that can be used to
+ * cancel
+ */
+struct GNUNET_DATASTORE_QueueEntry *
+GNUNET_DATASTORE_get_for_replication (struct GNUNET_DATASTORE_Handle *h,
+ unsigned int queue_priority,
+ unsigned int max_queue_size,
+ struct GNUNET_TIME_Relative timeout,
+ GNUNET_DATASTORE_DatumProcessor proc,
+ void *proc_cls);
+
+
+
+/**
+ * Cancel a datastore operation. The final callback from the
+ * operation must not have been done yet.
+ *
+ * @param qe operation to cancel
+ */
+void
+GNUNET_DATASTORE_cancel (struct GNUNET_DATASTORE_QueueEntry *qe);