From ac54a2d2b25a92723cbeced5942eb9414b74f22c Mon Sep 17 00:00:00 2001
From: Martine Lenders <mail@martine-lenders.eu>
Date: Mon, 22 Oct 2018 21:08:36 +0200
Subject: [PATCH] gnrc_pktbuf: add gnrc_pktbuf_reverse_snips() helper function
This allows for
a) testing the packet reversal properly in unittests
b) use it in other places than `gnrc_ipv6`'s receive function
---
sys/include/net/gnrc/pktbuf.h | 18 ++++++++++++++++++
sys/net/gnrc/pktbuf/gnrc_pktbuf.c | 23 +++++++++++++++++++++++
2 files changed, 41 insertions(+)
diff --git a/sys/include/net/gnrc/pktbuf.h b/sys/include/net/gnrc/pktbuf.h
index cf5cdb146c..3dc3994569 100644
--- a/sys/include/net/gnrc/pktbuf.h
+++ b/sys/include/net/gnrc/pktbuf.h
@@ -225,6 +225,24 @@ gnrc_pktsnip_t *gnrc_pktbuf_remove_snip(gnrc_pktsnip_t *pkt, gnrc_pktsnip_t *sni
*/
gnrc_pktsnip_t *gnrc_pktbuf_replace_snip(gnrc_pktsnip_t *pkt, gnrc_pktsnip_t *old, gnrc_pktsnip_t *add);
+/**
+ * @brief Reverses snip order of a packet in a write-protected manner.
+ *
+ * This can be used to change the send/receive order of a packet (see
+ * @ref gnrc_pktsnip_t)
+ *
+ * @note @p pkt is released on failure.
+ *
+ * @param[in] pkt A packet. When this function fails (due to a full packet
+ * packet buffer) @p pkt will be released.
+ *
+ * @return The reversed version of @p pkt on success
+ * @return NULL, when there is not enough space in the packet buffer to reverse
+ * the packet in a write-protected manner. @p pkt is released in that
+ * case.
+ */
+gnrc_pktsnip_t *gnrc_pktbuf_reverse_snips(gnrc_pktsnip_t *pkt);
+
/**
* @brief Duplicates pktsnip chain upto (including) a snip with the given type
* as a continuous snip.
diff --git a/sys/net/gnrc/pktbuf/gnrc_pktbuf.c b/sys/net/gnrc/pktbuf/gnrc_pktbuf.c
index 68631f7379..83e0a89e31 100644
--- a/sys/net/gnrc/pktbuf/gnrc_pktbuf.c
+++ b/sys/net/gnrc/pktbuf/gnrc_pktbuf.c
@@ -86,5 +86,28 @@ gnrc_pktsnip_t *gnrc_pktbuf_replace_snip(gnrc_pktsnip_t *pkt,
return pkt;
}
+gnrc_pktsnip_t *gnrc_pktbuf_reverse_snips(gnrc_pktsnip_t *pkt)
+{
+ gnrc_pktsnip_t *reversed = NULL, *ptr = pkt;
+
+ while (ptr != NULL) {
+ gnrc_pktsnip_t *next;
+
+ /* try to write-protect snip as its next-pointer is changed below */
+ pkt = gnrc_pktbuf_start_write(ptr); /* use pkt as temporary variable */
+ if (pkt == NULL) {
+ gnrc_pktbuf_release(reversed);
+ gnrc_pktbuf_release(ptr);
+ return NULL;
+ }
+ /* switch around pointers */
+ next = pkt->next;
+ pkt->next = reversed;
+ reversed = pkt;
+ ptr = next;
+ }
+ return reversed;
+}
+
/** @} */
--
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