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_HDR_PBUF_H
  #define LWIP_HDR_PBUF_H
  
  #include "lwip/opt.h"
  #include "lwip/err.h"
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  /** LWIP_SUPPORT_CUSTOM_PBUF==1: Custom pbufs behave much like their pbuf type
   * but they are allocated by external code (initialised by calling
   * pbuf_alloced_custom()) and when pbuf_free gives up their last reference, they
   * are freed by calling pbuf_custom->custom_free_function().
   * Currently, the pbuf_custom code is only needed for one specific configuration
   * of IP_FRAG, unless required by external driver/application code. */
  #ifndef LWIP_SUPPORT_CUSTOM_PBUF
  #define LWIP_SUPPORT_CUSTOM_PBUF ((IP_FRAG && !IP_FRAG_USES_STATIC_BUF && !LWIP_NETIF_TX_SINGLE_PBUF) || (LWIP_IPV6 && LWIP_IPV6_FRAG))
  #endif
  
  /* @todo: We need a mechanism to prevent wasting memory in every pbuf
     (TCP vs. UDP, IPv4 vs. IPv6: UDP/IPv4 packets may waste up to 28 bytes) */
  
  #define PBUF_TRANSPORT_HLEN 20
  #if LWIP_IPV6
  #define PBUF_IP_HLEN        40
  #else
  #define PBUF_IP_HLEN        20
  #endif
  
  typedef enum {
    PBUF_TRANSPORT,
    PBUF_IP,
    PBUF_LINK,
    PBUF_RAW_TX,
    PBUF_RAW
  } pbuf_layer;
  
  typedef enum {
    /** pbuf data is stored in RAM, used for TX mostly, struct pbuf and its payload
        are allocated in one piece of contiguous memory (so the first payload byte
        can be calculated from struct pbuf)
        pbuf_alloc() allocates PBUF_RAM pbufs as unchained pbufs (although that might
        change in future versions) */
    PBUF_RAM,
    /** pbuf data is stored in ROM, i.e. struct pbuf and its payload are located in
        totally different memory areas. Since it points to ROM, payload does not
        have to be copied when queued for transmission. */
    PBUF_ROM,
    /** pbuf comes from the pbuf pool. Much like PBUF_ROM but payload might change
        so it has to be duplicated when queued before transmitting, depending on
        who has a 'ref' to it. */
    PBUF_REF,
    /** pbuf payload refers to RAM. This one comes from a pool and should be used
        for RX. Payload can be chained (scatter-gather RX) but like PBUF_RAM, struct
        pbuf and its payload are allocated in one piece of contiguous memory (so
        the first payload byte can be calculated from struct pbuf) */
    PBUF_POOL
  } pbuf_type;
  
  
  /** indicates this packet's data should be immediately passed to the application */
  #define PBUF_FLAG_PUSH      0x01U
  /** indicates this is a custom pbuf: pbuf_free calls pbuf_custom->custom_free_function()
      when the last reference is released (plus custom PBUF_RAM cannot be trimmed) */
  #define PBUF_FLAG_IS_CUSTOM 0x02U
  /** indicates this pbuf is UDP multicast to be looped back */
  #define PBUF_FLAG_MCASTLOOP 0x04U
  /** indicates this pbuf was received as link-level broadcast */
  #define PBUF_FLAG_LLBCAST   0x08U
  /** indicates this pbuf was received as link-level multicast */
  #define PBUF_FLAG_LLMCAST   0x10U
  /** indicates this pbuf includes a TCP FIN flag */
  #define PBUF_FLAG_TCP_FIN   0x20U
  
  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;
  
    /** pbuf_type as u8_t instead of enum to save space */
    u8_t /*pbuf_type*/ type;
  
    /** misc flags */
    u8_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;
  };
  
  
  /** Helper struct for const-correctness only.
   * The only meaning of this one is to provide a const payload pointer
   * for PBUF_ROM type.
   */
  struct pbuf_rom {
    /** next pbuf in singly linked pbuf chain */
    struct pbuf *next;
  
    /** pointer to the actual data in the buffer */
    const void *payload;
  };
  
  #if LWIP_SUPPORT_CUSTOM_PBUF
  /** Prototype for a function to free a custom pbuf */
  typedef void (*pbuf_free_custom_fn)(struct pbuf *p);
  
  /** A custom pbuf: like a pbuf, but following a function pointer to free it. */
  struct pbuf_custom {
    /** The actual pbuf */
    struct pbuf pbuf;
    /** This function is called when pbuf_free deallocates this pbuf(_custom) */
    pbuf_free_custom_fn custom_free_function;
  };
  #endif /* LWIP_SUPPORT_CUSTOM_PBUF */
  
  #if LWIP_TCP && TCP_QUEUE_OOSEQ
  /** Define this to 0 to prevent freeing ooseq pbufs when the PBUF_POOL is empty */
  #ifndef PBUF_POOL_FREE_OOSEQ
  #define PBUF_POOL_FREE_OOSEQ 1
  #endif /* PBUF_POOL_FREE_OOSEQ */
  #if NO_SYS && PBUF_POOL_FREE_OOSEQ
  extern volatile u8_t pbuf_free_ooseq_pending;
  void pbuf_free_ooseq(void);
  /** When not using sys_check_timeouts(), call PBUF_CHECK_FREE_OOSEQ()
      at regular intervals from main level to check if ooseq pbufs need to be
      freed! */
  #define PBUF_CHECK_FREE_OOSEQ() do { if(pbuf_free_ooseq_pending) { \
    /* pbuf_alloc() reported PBUF_POOL to be empty -> try to free some \
       ooseq queued pbufs now */ \
    pbuf_free_ooseq(); }}while(0)
  #endif /* NO_SYS && PBUF_POOL_FREE_OOSEQ*/
  #endif /* LWIP_TCP && TCP_QUEUE_OOSEQ */
  
  /* Initializes the pbuf module. This call is empty for now, but may not be in future. */
  #define pbuf_init()
  
  struct pbuf *pbuf_alloc(pbuf_layer l, u16_t length, pbuf_type type);
  #if LWIP_SUPPORT_CUSTOM_PBUF
  struct pbuf *pbuf_alloced_custom(pbuf_layer l, u16_t length, pbuf_type type,
                                   struct pbuf_custom *p, void *payload_mem,
                                   u16_t payload_mem_len);
  #endif /* LWIP_SUPPORT_CUSTOM_PBUF */
  void pbuf_realloc(struct pbuf *p, u16_t size);
  u8_t pbuf_header(struct pbuf *p, s16_t header_size);
  u8_t pbuf_header_force(struct pbuf *p, s16_t header_size);
  void pbuf_ref(struct pbuf *p);
  u8_t pbuf_free(struct pbuf *p);
  u8_t pbuf_clen(struct pbuf *p);
  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, struct pbuf *p_from);
  u16_t pbuf_copy_partial(struct pbuf *p, void *dataptr, u16_t len, u16_t offset);
  err_t pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len);
  err_t pbuf_take_at(struct pbuf *buf, const void *dataptr, u16_t len, u16_t offset);
  struct pbuf *pbuf_skip(struct pbuf* in, u16_t in_offset, u16_t* out_offset);
  struct pbuf *pbuf_coalesce(struct pbuf *p, pbuf_layer layer);
  #if LWIP_CHECKSUM_ON_COPY
  err_t pbuf_fill_chksum(struct pbuf *p, u16_t start_offset, const void *dataptr,
                         u16_t len, u16_t *chksum);
  #endif /* LWIP_CHECKSUM_ON_COPY */
  #if LWIP_TCP && TCP_QUEUE_OOSEQ && LWIP_WND_SCALE
  void pbuf_split_64k(struct pbuf *p, struct pbuf **rest);
  #endif /* LWIP_TCP && TCP_QUEUE_OOSEQ && LWIP_WND_SCALE */
  
  u8_t pbuf_get_at(struct pbuf* p, u16_t offset);
  void pbuf_put_at(struct pbuf* p, u16_t offset, u8_t data);
  u16_t pbuf_memcmp(struct pbuf* p, u16_t offset, const void* s2, u16_t n);
  u16_t pbuf_memfind(struct pbuf* p, const void* mem, u16_t mem_len, u16_t start_offset);
  u16_t pbuf_strstr(struct pbuf* p, const char* substr);
  
  #ifdef __cplusplus
  }
  #endif
  
  #endif /* LWIP_HDR_PBUF_H */
  
  