sapi: Add rtems_chain_get_first_unprotected()

Close #2459.

3 files changed, 50 insertions, 0 deletions

diff --git a/cpukit/sapi/include/rtems/chain.h b/cpukit/sapi/include/rtems/chain.h
index 8da355da0c..4d586ff06e 100644
--- a/cpukit/sapi/include/rtems/chain.h
+++ b/cpukit/sapi/include/rtems/chain.h
@@ -624,6 +624,16 @@ RTEMS_INLINE_ROUTINE rtems_chain_node *rtems_chain_get_unprotected(
 }
 
 /**
+ * @brief See _Chain_Get_first_unprotected().
+ */
+RTEMS_INLINE_ROUTINE rtems_chain_node *rtems_chain_get_first_unprotected(
+  rtems_chain_control *the_chain
+)
+{
+  return _Chain_Get_first_unprotected( the_chain );
+}
+
+/**
  * @brief Insert a node on a chain
  *
  * This routine inserts @a the_node on a chain immediately following
diff --git a/doc/user/chains.t b/doc/user/chains.t
index e5dffc24df..79e5984ffb 100644
--- a/doc/user/chains.t
+++ b/doc/user/chains.t
@@ -35,6 +35,7 @@ provided by RTEMS is:
 @item @code{@value{DIRPREFIX}chain_extract_unprotected} - Extract the node from the chain (unprotected)
 @item @code{@value{DIRPREFIX}chain_get} - Return the first node on the chain
 @item @code{@value{DIRPREFIX}chain_get_unprotected} - Return the first node on the chain (unprotected)
+@item @code{@value{DIRPREFIX}chain_get_first_unprotected} - Get the first node on the chain (unprotected)
 @item @code{@value{DIRPREFIX}chain_insert} - Insert the node into the chain
 @item @code{@value{DIRPREFIX}chain_insert_unprotected} - Insert the node into the chain (unprotected)
 @item @code{@value{DIRPREFIX}chain_append} - Append the node to chain
@@ -661,6 +662,38 @@ interrupts.
 @c
 @c
 @page
+@subsection Get the First Node (unprotected)
+
+@cindex chain get first node
+
+@subheading CALLING SEQUENCE:
+
+@ifset is-C
+@findex @value{DIRPREFIX}chain_get_first_unprotected
+@example
+@value{DIRPREFIX}chain_node *@value{DIRPREFIX}chain_get_first_unprotected(
+  @value{DIRPREFIX}chain_control *the_chain
+);
+@end example
+@end ifset
+
+@subheading RETURNS:
+
+A pointer to the former first node is returned.
+
+@subheading DESCRIPTION:
+
+Removes the first node from the chain and returns a pointer to it.  In case the
+chain was empty, then the results are unpredictable.
+
+@subheading NOTES:
+
+The function does nothing to ensure the atomicity of the operation.
+
+@c
+@c
+@c
+@page
 @subsection Insert a Node
 
 @cindex chain insert a node
diff --git a/testsuites/sptests/spchain/init.c b/testsuites/sptests/spchain/init.c
index ca2e135e95..476629b548 100644
--- a/testsuites/sptests/spchain/init.c
+++ b/testsuites/sptests/spchain/init.c
@@ -117,6 +117,13 @@ static void test_chain_first_and_last(void)
   puts( "INIT - Verify rtems_chain_is_last" );
   cnode = rtems_chain_last(&chain);
   rtems_test_assert( rtems_chain_is_last( cnode ) );
+
+  cnode = rtems_chain_get_first_unprotected( &chain );
+  rtems_test_assert( cnode == &node1 );
+  cnode = rtems_chain_first( &chain );
+  rtems_test_assert( cnode == &node2 );
+  cnode = rtems_chain_last( &chain );
+  rtems_test_assert( cnode == &node2 );
 }
 
 static void test_chain_with_notification(void)