mm/iob: add support of nonblock iob_clone

Signed-off-by: chao an <anchao@xiaomi.com>

Documentation/reference/os/iob.rst

@@ -267,7 +267,8 @@ Public Function Prototypes
   buffer starting at ``offset`` in the I/O buffer, returning that
   actual number of bytes copied out.
 
-.. c:function:: int iob_clone(FAR struct iob_s *iob1, FAR struct iob_s *iob2, bool throttled)
+.. c:function:: int iob_clone(FAR struct iob_s *iob1, FAR struct iob_s *iob2, \
+                   bool throttled, bool block);
 
   Duplicate (and pack) the data in ``iob1`` in
   ``iob2``. ``iob2`` must be empty.

include/nuttx/mm/iob.h

@@ -464,8 +464,8 @@ unsigned int iob_tailroom(FAR struct iob_s *iob);
  *
  ****************************************************************************/
 
-int iob_clone(FAR struct iob_s *iob1,
-              FAR struct iob_s *iob2, bool throttled);
+int iob_clone(FAR struct iob_s *iob1, FAR struct iob_s *iob2,
+              bool throttled, bool block);
 
 /****************************************************************************
  * Name: iob_concat

mm/iob/iob_clone.c

@@ -53,7 +53,8 @@
  *
  ****************************************************************************/
 
-int iob_clone(FAR struct iob_s *iob1, FAR struct iob_s *iob2, bool throttled)
+int iob_clone(FAR struct iob_s *iob1, FAR struct iob_s *iob2,
+              bool throttled, bool block)
 {
   FAR uint8_t *src;
   FAR uint8_t *dest;
@@ -145,7 +146,15 @@ int iob_clone(FAR struct iob_s *iob1, FAR struct iob_s *iob2, bool throttled)
            * destination I/O buffer chain.
            */
 
-          next = iob_alloc(throttled);
+          if (block)
+            {
+              next = iob_alloc(throttled);
+            }
+          else
+            {
+              next = iob_tryalloc(throttled);
+            }
+
           if (!next)
             {
               ioberr("ERROR: Failed to allocate an I/O buffer\n");