[nuttx] 03/05: mm/cirbuf: Fix cannot continue read when tail > head

[xiaoxiang]

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xiaoxiang pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/nuttx.git

commit e503f86256c481bfd439ae469235b5435100ac42
Author: yintao <yin...@xiaomi.com>
AuthorDate: Wed Jul 5 21:47:36 2023 +0800

    mm/cirbuf: Fix cannot continue read when tail > head
    
    when head=0, tail has not yet rolled back, and at this time tail>head still 
has data to read
    
    Signed-off-by: yintao <yin...@xiaomi.com>
---
 mm/circbuf/circbuf.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/mm/circbuf/circbuf.c b/mm/circbuf/circbuf.c
index b85a029f59..f9fac1fdcf 100644
--- a/mm/circbuf/circbuf.c
+++ b/mm/circbuf/circbuf.c
@@ -301,11 +301,16 @@ ssize_t circbuf_peekat(FAR struct circbuf_s *circ, size_t 
pos,
 
   DEBUGASSERT(circ);
 
-  if (!circ->size || pos >= circ->head)
+  if (!circ->size)
     {
       return 0;
     }
 
+  if (circ->head - pos > circ->head - circ->tail)
+    {
+      pos = circ->tail;
+    }
+
   len = circ->head - pos;
   off = pos % circ->size;