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net/iob/iob_peek_queue.c

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+/****************************************************************************
+ * net/iob/iob_peek_queue.c
+ *
+ *   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#if defined(CONFIG_DEBUG) && defined(CONFIG_IOB_DEBUG)
+/* Force debug output (from this file only) */
+
+#  undef  CONFIG_DEBUG_NET
+#  define CONFIG_DEBUG_NET 1
+#endif
+
+#include <debug.h>
+
+#include <nuttx/net/iob.h>
+
+#include "iob.h"
+
+#if CONFIG_IOB_NCHAINS > 0
+
+/****************************************************************************
+ * Pre-processor Definitions
+ ****************************************************************************/
+
+#ifndef NULL
+#  define NULL ((FAR void *)0)
+#endif
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: iob_peek_queue
+ *
+ * Description:
+ *   Return a reference to the I/O buffer chain at the head of a queue. This
+ *   is similar to iob_remove_queue except that the I/O buffer chain is in
+ *   place at the head of the queue.  The I/O buffer chain may safely be
+ *   modified by the caller but must be removed from the queue before it can
+ *   be freed.
+ *
+ * Returned Value:
+ *   Returns a reference to the I/O buffer chain at the head of the queue.
+ *
+ ****************************************************************************/
+
+FAR struct iob_s *iob_peek_queue(FAR struct iob_queue_s *iobq)
+{
+  FAR struct iob_qentry_s *qentry;
+  FAR struct iob_s *iob = NULL;
+
+  /* Peek at the I/O buffer chain container at the head of the queue */
+
+  qentry = iobq->qh_head;
+  if (qentry)
+    {
+      /* Return the I/O buffer chain from the container */
+
+      iob = qentry->qe_head;
+    }
+
+  return iob;
+}
+
+#endif /* CONFIG_IOB_NCHAINS > 0 */