[GitHub] [mynewt-core] kasjer commented on a change in pull request #2075: kernel/os: Add os_mbuf_pack_chains

[GitBox <gi...@apache.org>]

kasjer commented on a change in pull request #2075: kernel/os: Add os_mbuf_pack_chains
URL: https://github.com/apache/mynewt-core/pull/2075#discussion_r340373238
 
 

 ##########
 File path: kernel/os/src/os_mbuf.c
 ##########
 @@ -1036,3 +1036,90 @@ os_mbuf_widen(struct os_mbuf *om, uint16_t off, uint16_t len)
 
     return 0;
 }
+
+struct os_mbuf *
+os_mbuf_pack_chains(struct os_mbuf *m1, struct os_mbuf *m2)
+{
+    uint16_t rem_len;
+    uint16_t copylen;
+    uint8_t *dptr;
+    struct os_mbuf *cur;
+    struct os_mbuf *next;
+
+    /* If m1 is NULL, return NULL */
+    if (m1 == NULL) {
+        return NULL;
+    }
+
+    /*
+     * Concatenate the two chains to start. This will discard packet header in
+     * m2 and adjust packet length in m1 if m1 has a packet header.
+     */
+    if (m2 != NULL) {
+        os_mbuf_concat(m1, m2);
+    }
+
+    cur = m1;
+    while (1) {
+        /* If there is leading space in the mbuf, move data up */
+        if (OS_MBUF_LEADINGSPACE(cur)) {
+            dptr = &cur->om_databuf[0];
+            if (OS_MBUF_IS_PKTHDR(cur)) {
+                dptr += cur->om_pkthdr_len;
+            }
+            memmove(dptr, cur->om_data, cur->om_len);
+            cur->om_data = dptr;
+        }
+
+        /* Set pointer to where we will begin copying data in current mbuf */
+        dptr = cur->om_data + cur->om_len;
+
+        /* Get a pointer to the next buf we want to absorb */
+        next = SLIST_NEXT(cur, om_next);
+
+        /*
+         * Is there trailing space in the mbuf? If so, copy data from
+         * following mbufs into the current mbuf
+         */
+        rem_len = OS_MBUF_TRAILINGSPACE(cur);
+        while (rem_len && next) {
 
 Review comment:
   in other cases length is compared to 0 and next to NULL while here is shorter version is used. Not that it matters.

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