text: /**
   * @file
   * Network buffer management
   *
   */
   
  /*
   * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
   * All rights reserved. 
   * 
   * 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. The name of the author may not be used to endorse or promote products
   *    derived from this software without specific prior written permission. 
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
   *
   * This file is part of the lwIP TCP/IP stack.
   * 
   * Author: Adam Dunkels <adam@sics.se>
   *
   */
  
  #include "lwip/opt.h"
  
  #if LWIP_NETCONN /* don't build if not configured for use in lwipopts.h */
  
  #include "lwip/netbuf.h"
  #include "lwip/memp.h"
  
  #include <string.h>
  
  /**
   * Create (allocate) and initialize a new netbuf.
   * The netbuf doesn't yet contain a packet buffer!
   *
   * @return a pointer to a new netbuf
   *         NULL on lack of memory
   */
  struct
  netbuf *netbuf_new(void)
  {
    struct netbuf *buf;
  
    buf = memp_malloc(MEMP_NETBUF);
    if (buf != NULL) {
      buf->p = NULL;
      buf->ptr = NULL;
      buf->addr = NULL;
      buf->port = 0;
  #if LWIP_NETBUF_RECVINFO
      buf->toaddr = NULL;
      buf->toport = 0;
  #endif /* LWIP_NETBUF_RECVINFO */
      return buf;
    } else {
      return NULL;
    }
  }
  
  /**
   * Deallocate a netbuf allocated by netbuf_new().
   *
   * @param buf pointer to a netbuf allocated by netbuf_new()
   */
  void
  netbuf_delete(struct netbuf *buf)
  {
    if (buf != NULL) {
      if (buf->p != NULL) {
        pbuf_free(buf->p);
        buf->p = buf->ptr = NULL;
      }
      memp_free(MEMP_NETBUF, buf);
    }
  }
  
  /**
   * Allocate memory for a packet buffer for a given netbuf.
   *
   * @param buf the netbuf for which to allocate a packet buffer
   * @param size the size of the packet buffer to allocate
   * @return pointer to the allocated memory
   *         NULL if no memory could be allocated
   */
  void *
  netbuf_alloc(struct netbuf *buf, u16_t size)
  {
    LWIP_ERROR("netbuf_alloc: invalid buf", (buf != NULL), return NULL;);
  
    /* Deallocate any previously allocated memory. */
    if (buf->p != NULL) {
      pbuf_free(buf->p);
    }
    buf->p = pbuf_alloc(PBUF_TRANSPORT, size, PBUF_RAM);
    if (buf->p == NULL) {
       return NULL;
    }
    LWIP_ASSERT("check that first pbuf can hold size",
               (buf->p->len >= size));
    buf->ptr = buf->p;
    return buf->p->payload;
  }
  
  /**
   * Free the packet buffer included in a netbuf
   *
   * @param buf pointer to the netbuf which contains the packet buffer to free
   */
  void
  netbuf_free(struct netbuf *buf)
  {
    LWIP_ERROR("netbuf_free: invalid buf", (buf != NULL), return;);
    if (buf->p != NULL) {
      pbuf_free(buf->p);
    }
    buf->p = buf->ptr = NULL;
  }
  
  /**
   * Let a netbuf reference existing (non-volatile) data.
   *
   * @param buf netbuf which should reference the data
   * @param dataptr pointer to the data to reference
   * @param size size of the data
   * @return ERR_OK if data is referenced
   *         ERR_MEM if data couldn't be referenced due to lack of memory
   */
  err_t
  netbuf_ref(struct netbuf *buf, const void *dataptr, u16_t size)
  {
    LWIP_ERROR("netbuf_ref: invalid buf", (buf != NULL), return ERR_ARG;);
    if (buf->p != NULL) {
      pbuf_free(buf->p);
    }
    buf->p = pbuf_alloc(PBUF_TRANSPORT, 0, PBUF_REF);
    if (buf->p == NULL) {
      buf->ptr = NULL;
      return ERR_MEM;
    }
    buf->p->payload = (void*)dataptr;
    buf->p->len = buf->p->tot_len = size;
    buf->ptr = buf->p;
    return ERR_OK;
  }
  
  /**
   * Chain one netbuf to another (@see pbuf_chain)
   *
   * @param head the first netbuf
   * @param tail netbuf to chain after head, freed by this function, may not be reference after returning
   */
  void
  netbuf_chain(struct netbuf *head, struct netbuf *tail)
  {
    LWIP_ERROR("netbuf_ref: invalid head", (head != NULL), return;);
    LWIP_ERROR("netbuf_chain: invalid tail", (tail != NULL), return;);
    pbuf_cat(head->p, tail->p);
    head->ptr = head->p;
    memp_free(MEMP_NETBUF, tail);
  }
  
  /**
   * Get the data pointer and length of the data inside a netbuf.
   *
   * @param buf netbuf to get the data from
   * @param dataptr pointer to a void pointer where to store the data pointer
   * @param len pointer to an u16_t where the length of the data is stored
   * @return ERR_OK if the information was retreived,
   *         ERR_BUF on error.
   */
  err_t
  netbuf_data(struct netbuf *buf, void **dataptr, u16_t *len)
  {
    LWIP_ERROR("netbuf_data: invalid buf", (buf != NULL), return ERR_ARG;);
    LWIP_ERROR("netbuf_data: invalid dataptr", (dataptr != NULL), return ERR_ARG;);
    LWIP_ERROR("netbuf_data: invalid len", (len != NULL), return ERR_ARG;);
  
    if (buf->ptr == NULL) {
      return ERR_BUF;
    }
    *dataptr = buf->ptr->payload;
    *len = buf->ptr->len;
    return ERR_OK;
  }
  
  /**
   * Move the current data pointer of a packet buffer contained in a netbuf
   * to the next part.
   * The packet buffer itself is not modified.
   *
   * @param buf the netbuf to modify
   * @return -1 if there is no next part
   *         1  if moved to the next part but now there is no next part
   *         0  if moved to the next part and there are still more parts
   */
  s8_t
  netbuf_next(struct netbuf *buf)
  {
    LWIP_ERROR("netbuf_free: invalid buf", (buf != NULL), return -1;);
    if (buf->ptr->next == NULL) {
      return -1;
    }
    buf->ptr = buf->ptr->next;
    if (buf->ptr->next == NULL) {
      return 1;
    }
    return 0;
  }
  
  /**
   * Move the current data pointer of a packet buffer contained in a netbuf
   * to the beginning of the packet.
   * The packet buffer itself is not modified.
   *
   * @param buf the netbuf to modify
   */
  void
  netbuf_first(struct netbuf *buf)
  {
    LWIP_ERROR("netbuf_free: invalid buf", (buf != NULL), return;);
    buf->ptr = buf->p;
  }
  
  #endif /* LWIP_NETCONN */
  