pbuf.h

DM642上的TCP/IP代码 LWIP 是TCP/ IP 在嵌入式系统中应用很多的代码

#ifndef __LWIP_PBUF_H__
#define __LWIP_PBUF_H__

#include "lwdef.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__ */