text: /*
   * 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>
   *
   */
  
  #ifndef __LWIP_PBUF_H__
  #define __LWIP_PBUF_H__
  
  #include "arch/cc.h"
  
  #define PBUF_TRANSPORT_HLEN 20
  #define PBUF_IP_HLEN        20
  
  typedef enum {
    PBUF_TRANSPORT,
    PBUF_IP,
    PBUF_LINK,
    PBUF_RAW
  } pbuf_layer;
  
  typedef enum {
    PBUF_RAM,
    PBUF_ROM,
    PBUF_REF,
    PBUF_POOL
  } pbuf_flag;
  
  /* Definitions for the pbuf flag field. These are NOT the flags that
   * are passed to pbuf_alloc(). */
  #define PBUF_FLAG_RAM   0x00U    /* Flags that pbuf data is stored in RAM */
  #define PBUF_FLAG_ROM   0x01U    /* Flags that pbuf data is stored in ROM */
  #define PBUF_FLAG_POOL  0x02U    /* Flags that the pbuf comes from the pbuf pool */
  #define PBUF_FLAG_REF   0x04U    /* Flags thet the pbuf payload refers to RAM */
  
  /** indicates this packet was broadcast on the link */
  #define PBUF_FLAG_LINK_BROADCAST 0x80U
  
  struct pbuf {
    /** next pbuf in singly linked pbuf chain */
    struct pbuf *next;
  
    /** pointer to the actual data in the buffer */
    void *payload;
  
    /**
     * total length of this buffer and all next buffers in chain
     * belonging to the same packet.
     *
     * For non-queue packet chains this is the invariant:
     * p->tot_len == p->len + (p->next? p->next->tot_len: 0)
     */
    u16_t tot_len;
  
    /** length of this buffer */
    u16_t len;
  
    /** flags telling the type of pbuf, see PBUF_FLAG_ */
    u16_t flags;
  
    /**
     * the reference count always equals the number of pointers
     * that refer to this pbuf. This can be pointers from an application,
     * the stack itself, or pbuf->next pointers from a chain.
     */
    u16_t ref;
  
  };
  
  void pbuf_init(void);
  
  struct pbuf *pbuf_alloc(pbuf_layer l, u16_t size, pbuf_flag flag);
  void pbuf_realloc(struct pbuf *p, u16_t size);
  u8_t pbuf_header(struct pbuf *p, s16_t header_size);
  void pbuf_ref(struct pbuf *p);
  void pbuf_ref_chain(struct pbuf *p);
  u8_t pbuf_free(struct pbuf *p);
  u8_t pbuf_clen(struct pbuf *p);
  void pbuf_cat(struct pbuf *h, struct pbuf *t);
  void pbuf_chain(struct pbuf *h, struct pbuf *t);
  struct pbuf *pbuf_take(struct pbuf *f);
  struct pbuf *pbuf_dechain(struct pbuf *p);
  void pbuf_queue(struct pbuf *p, struct pbuf *n);
  struct pbuf * pbuf_dequeue(struct pbuf *p);
  
  #endif /* __LWIP_PBUF_H__ */
  