[agroal#463] Deque poll/peek last

src/include/deque.h

@@ -128,6 +128,19 @@ pgagroal_deque_add_with_config(struct deque* deque, char* tag, uintptr_t data, s
 uintptr_t
 pgagroal_deque_poll(struct deque* deque, char** tag);
 
+/**
+ * Retrieve value and remove the node from deque's tail.
+ * Note that if the value was copied into node,
+ * this function will return the original value and tag
+ * rather than making a copy of it.
+ * This function is thread safe, but the returned value is not protected
+ * @param deque The deque
+ * @param tag [out] Optional, tag will be returned through if not NULL
+ * @return The value data if deque's not empty, otherwise 0
+ */
+uintptr_t
+pgagroal_deque_poll_last(struct deque* deque, char** tag);
+
 /**
  * Retrieve value without removing the node from deque's head.
  * Note that if the value was copied into node,
@@ -141,6 +154,19 @@ pgagroal_deque_poll(struct deque* deque, char** tag);
 uintptr_t
 pgagroal_deque_peek(struct deque* deque, char** tag);
 
+/**
+ * Retrieve value without removing the node from deque's tail.
+ * Note that if the value was copied into node,
+ * this function will return the original value and tag
+ * rather than making a copy of it.
+ * This function is thread safe, but the returned value is not protected
+ * @param deque The deque
+ * @param tag [out] Optional, tag will be returned through if not NULL
+ * @return The value data if deque's not empty, otherwise 0
+ */
+uintptr_t
+pgagroal_deque_peek_last(struct deque* deque, char** tag);
+
 /**
  * Get the data for the specified tag
  * @param deque The deque

src/libpgagroal/deque.c

@@ -176,6 +176,42 @@ pgagroal_deque_poll(struct deque* deque, char** tag)
    return data;
 }
 
+uintptr_t
+pgagroal_deque_poll_last(struct deque* deque, char** tag)
+{
+   struct deque_node* tail = NULL;
+   struct value* val = NULL;
+   uintptr_t data = 0;
+   if (deque == NULL || pgagroal_deque_size(deque) == 0)
+   {
+      return 0;
+   }
+   deque_write_lock(deque);
+   tail = deque->end->prev;
+   if (tail == deque->start)
+   {
+      deque_unlock(deque);
+      return 0;
+   }
+   // remove node
+   deque->end->prev = tail->prev;
+   tail->prev->next = deque->end;
+   deque->size--;
+
+   val = tail->data;
+   if (tag != NULL)
+   {
+      *tag = tail->tag;
+   }
+   free(tail);
+
+   data = pgagroal_value_data(val);
+   free(val);
+
+   deque_unlock(deque);
+   return data;
+}
+
 uintptr_t
 pgagroal_deque_peek(struct deque* deque, char** tag)
 {
@@ -202,6 +238,32 @@ pgagroal_deque_peek(struct deque* deque, char** tag)
    return pgagroal_value_data(val);
 }
 
+uintptr_t
+pgagroal_deque_peek_last(struct deque* deque, char** tag)
+{
+   struct deque_node* tail = NULL;
+   struct value* val = NULL;
+   if (deque == NULL || pgagroal_deque_size(deque) == 0)
+   {
+      return 0;
+   }
+   deque_read_lock(deque);
+   tail = deque->end->prev;
+   // this should not happen when size is not 0, but just in case
+   if (tail == deque->start)
+   {
+      deque_unlock(deque);
+      return 0;
+   }
+   val = tail->data;
+   if (tag != NULL)
+   {
+      *tag = tail->tag;
+   }
+   deque_unlock(deque);
+   return pgagroal_value_data(val);
+}
+
 uintptr_t
 pgagroal_deque_get(struct deque* deque, char* tag)
 {