Initial version of CBUFF tail detach version.

The tail/consumer disconnection is quite problematic
because no message intended to be consumed by tail
can be left in the buffer because else i prevent
reuse of the buffer space.

The ul_cbuff_tail_detach_onestep() function returns
value 0 if there is no message left and tail is disconnected.
Value 1 indicates that at least one more iterations is required.
Value 2 is returned if there are partially filed messages
preventing immediate next step. Wait for consumer
wake event is required in this case.

Signed-off-by: Pavel Pisa <pisa@cmp.felk.cvut.cz>

diff --git a/ulut/ul_cbuff.h b/ulut/ul_cbuff.h
index 29d662f49032e57b0516e2d507312cee7afd6a0b..e9a74e3b5a00138399e5978161a20655108ba0a3 100644 (file)
--- a/ulut/ul_cbuff.h
+++ b/ulut/ul_cbuff.h
@@ -108,6 +108,7 @@ int ul_cbuff_tail_test(ul_cbuff_t *buff, ul_cbuff_tail_info_t *tail_info);
 int ul_cbuff_tail_release(ul_cbuff_t *buff, ul_cbuff_tail_info_t *tail_info);
 int ul_cbuff_tail_next(ul_cbuff_t *buff, ul_cbuff_tail_info_t *tail_info);
 int ul_cbuff_tail_state_update(ul_cbuff_t *buff, int release_result, ul_cbuff_loc_t loc, ul_cbuff_loc_t loc_next);
+int ul_cbuff_tail_detach_onestep(ul_cbuff_t *buff, ul_cbuff_tail_info_t *tail_info);
 void ul_cbuff_data_do_wrap(ul_cbuff_data_info_t *data_info);
 int ul_cbuff_data_at_once(ul_cbuff_data_info_t *data_info, void **pptr, int size);
 int ul_cbuff_put_data(ul_cbuff_data_info_t *data_info, const void *data, int size);
@@ -341,6 +342,39 @@ ul_cbuff_tail_state_update(ul_cbuff_t *buff, int release_result, ul_cbuff_loc_t
   }
 }
 
+ul_cbuff_inline int
+ul_cbuff_tail_detach_onestep(ul_cbuff_t *buff, ul_cbuff_tail_info_t *tail_info)
+{
+  ul_cbuff_state_t *state=buff->state;
+  ul_cbuff_loc_t loc;
+  ul_cbuff_loc_t loc_next;
+  unsigned msg_readers;
+
+  if(tail_info->msg_head==NULL)
+    return 0;
+
+  loc = ul_cbuff_head_loc(buff, tail_info->msg_head);
+
+  if(loc!=state->head) {
+    if(!ul_cbuff_is_ready(tail_info->msg_head))
+      return 2;
+    msg_readers=tail_info->msg_head->flags&UL_CBUFF_MSG_READERS;
+    loc_next=ul_cbuff_next_loc(buff, tail_info->msg_head);
+    if(msg_readers)
+      tail_info->msg_head->flags--;
+    tail_info->msg_head=(ul_cbuff_msg_head_t *)(buff->buff_start+loc_next);
+    ul_cbuff_tail_state_update(buff, msg_readers<=1? 1: 0, loc, loc_next);
+    return 1;
+  }
+
+  if(state->readers>0)
+    state->readers--;
+  tail_info->msg_head=NULL;
+  tail_info->data.ptr=NULL;
+  return 0;
+}
+
+
 ul_cbuff_inline void
 ul_cbuff_data_do_wrap(ul_cbuff_data_info_t *data_info)
 {