pbuf: Add pbuf_copy_partial_pbuf library function

Like pbuf_copy, but can copy part of a pbuf to an offset in another.
pbuf_copy now uses this function internally.

Signed-off-by: Simon Goldschmidt <goldsimon@gmx.de>

src/core/pbuf.c

@@ -960,54 +960,88 @@ pbuf_dechain(struct pbuf *p)
 err_t
 pbuf_copy(struct pbuf *p_to, const struct pbuf *p_from)
 {
-  size_t offset_to = 0, offset_from = 0, len;
-
   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy(%p, %p)\n",
               (const void *)p_to, (const void *)p_from));
 
+  LWIP_ERROR("pbuf_copy: invalid source", p_from != NULL, return ERR_ARG;);
+  return pbuf_copy_partial_pbuf(p_to, p_from, p_from->tot_len, 0);
+}
+
+/**
+ * @ingroup pbuf
+ * Copy part or all of one packet buffer into another, to a specified offset.
+ *
+ * @note Only data in one packet is copied, no packet queue!
+ * @note Argument order is shared with pbuf_copy, but different than pbuf_copy_partial.
+ *
+ * @param p_to pbuf destination of the copy
+ * @param p_from pbuf source of the copy
+ * @param copy_len number of bytes to copy
+ * @param offset offset in destination pbuf where to copy to
+ *
+ * @return ERR_OK if copy_len bytes were copied
+ *         ERR_ARG if one of the pbufs is NULL or p_from is shorter than copy_len
+ *                 or p_to is not big enough to hold copy_len at offset
+ *         ERR_VAL if any of the pbufs are part of a queue
+ */
+err_t
+pbuf_copy_partial_pbuf(struct pbuf *p_to, const struct pbuf *p_from, u16_t copy_len, u16_t offset)
+{
+  size_t offset_to = offset, offset_from = 0, len_calc;
+  u16_t len;
+
+  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy_partial_pbuf(%p, %p, %"U16_F", %"U16_F")\n",
+              (const void *)p_to, (const void *)p_from, copy_len, offset));
+
+  /* is the copy_len in range? */
+  LWIP_ERROR("pbuf_copy_partial_pbuf: copy_len bigger than source", ((p_from != NULL) &&
+             (p_from->tot_len >= copy_len)), return ERR_ARG;);
   /* is the target big enough to hold the source? */
-  LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
+  LWIP_ERROR("pbuf_copy_partial_pbuf: target not big enough", ((p_to != NULL) &&
-             (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
+             (p_to->tot_len >= (offset + copy_len))), return ERR_ARG;);
 
   /* iterate through pbuf chain */
   do {
     /* copy one part of the original chain */
     if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
       /* complete current p_from fits into current p_to */
-      len = p_from->len - offset_from;
+      len_calc = p_from->len - offset_from;
     } else {
       /* current p_from does not fit into current p_to */
-      len = p_to->len - offset_to;
+      len_calc = p_to->len - offset_to;
     }
+    len = (u16_t)LWIP_MIN(copy_len, len_calc);
     MEMCPY((u8_t *)p_to->payload + offset_to, (u8_t *)p_from->payload + offset_from, len);
     offset_to += len;
     offset_from += len;
+    copy_len -= len;
     LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
     LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
     if (offset_from >= p_from->len) {
       /* on to next p_from (if any) */
       offset_from = 0;
       p_from = p_from->next;
+      LWIP_ERROR("p_from != NULL", (p_from != NULL) || (copy_len == 0), return ERR_ARG;);
     }
     if (offset_to == p_to->len) {
       /* on to next p_to (if any) */
       offset_to = 0;
       p_to = p_to->next;
-      LWIP_ERROR("p_to != NULL", (p_to != NULL) || (p_from == NULL), return ERR_ARG;);
+      LWIP_ERROR("p_to != NULL", (p_to != NULL) || (copy_len == 0), return ERR_ARG;);
     }
 
     if ((p_from != NULL) && (p_from->len == p_from->tot_len)) {
       /* don't copy more than one packet! */
-      LWIP_ERROR("pbuf_copy() does not allow packet queues!",
+      LWIP_ERROR("pbuf_copy_partial_pbuf() does not allow packet queues!",
                  (p_from->next == NULL), return ERR_VAL;);
     }
     if ((p_to != NULL) && (p_to->len == p_to->tot_len)) {
       /* don't copy more than one packet! */
-      LWIP_ERROR("pbuf_copy() does not allow packet queues!",
+      LWIP_ERROR("pbuf_copy_partial_pbuf() does not allow packet queues!",
                  (p_to->next == NULL), return ERR_VAL;);
     }
-  } while (p_from);
+  } while (copy_len);
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy: end of chain reached.\n"));
+  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy_partial_pbuf: copy complete.\n"));
   return ERR_OK;
 }
 

src/include/lwip/pbuf.h

@@ -296,6 +296,7 @@ void pbuf_cat(struct pbuf *head, struct pbuf *tail);
 void pbuf_chain(struct pbuf *head, struct pbuf *tail);
 struct pbuf *pbuf_dechain(struct pbuf *p);
 err_t pbuf_copy(struct pbuf *p_to, const struct pbuf *p_from);
+err_t pbuf_copy_partial_pbuf(struct pbuf *p_to, const struct pbuf *p_from, u16_t copy_len, u16_t offset);
 u16_t pbuf_copy_partial(const struct pbuf *p, void *dataptr, u16_t len, u16_t offset);
 void *pbuf_get_contiguous(const struct pbuf *p, void *buffer, size_t bufsize, u16_t len, u16_t offset);
 err_t pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len);