text: /*
   * mbuf.h
   *		Memory buffer operations.
   *
   * Copyright (c) 2005 Marko Kreen
   * 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.
   *
   * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
   *
   * contrib/pgcrypto/mbuf.h
   */
  
  #ifndef __PX_MBUF_H
  #define __PX_MBUF_H
  
  typedef struct MBuf MBuf;
  typedef struct PushFilter PushFilter;
  typedef struct PullFilter PullFilter;
  typedef struct PushFilterOps PushFilterOps;
  typedef struct PullFilterOps PullFilterOps;
  
  struct PushFilterOps {
      /*
       * should return needed buffer size, 0- no buffering, <0 on error if NULL,
       * no buffering, and priv=init_arg
       */
      int (*init)(PushFilter* next, void* init_arg, void** priv_p);
  
      /*
       * send data to next.  should consume all? if null, it will be simply
       * copied (in-place) returns 0 on error
       */
      int (*push)(PushFilter* next, void* priv, const uint8* src, int len);
      int (*flush)(PushFilter* next, void* priv);
      void (*free)(void* priv);
  };
  
  struct PullFilterOps {
      /*
       * should return needed buffer size, 0- no buffering, <0 on error if NULL,
       * no buffering, and priv=init_arg
       */
      int (*init)(void** priv_p, void* init_arg, PullFilter* src);
  
      /*
       * request data from src, put result ptr to data_p can use ptr from src or
       * use buf as work area if NULL in-place copy
       */
      int (*pull)(void* priv, PullFilter* src, int len, uint8** data_p, uint8* buf, int buflen);
      void (*free)(void* priv);
  };
  
  /*
   * Memory buffer
   */
  MBuf* mbuf_create(int len);
  MBuf* mbuf_create_from_data(uint8* data, int len);
  int mbuf_tell(MBuf* mbuf);
  int mbuf_avail(MBuf* mbuf);
  int mbuf_size(MBuf* mbuf);
  int mbuf_grab(MBuf* mbuf, int len, uint8** data_p);
  int mbuf_steal_data(MBuf* mbuf, uint8** data_p);
  int mbuf_append(MBuf* dst, const uint8* buf, int cnt);
  int mbuf_rewind(MBuf* mbuf);
  int mbuf_free(MBuf* mbuf);
  
  /*
   * Push filter
   */
  int pushf_create(PushFilter** res, const PushFilterOps* ops, void* init_arg, PushFilter* next);
  int pushf_write(PushFilter* mp, const uint8* data, int len);
  void pushf_free_all(PushFilter* mp);
  void pushf_free(PushFilter* mp);
  int pushf_flush(PushFilter* mp);
  
  int pushf_create_mbuf_writer(PushFilter** mp_p, MBuf* mbuf);
  
  /*
   * Pull filter
   */
  int pullf_create(PullFilter** res, const PullFilterOps* ops, void* init_arg, PullFilter* src);
  int pullf_read(PullFilter* mp, int len, uint8** data_p);
  int pullf_read_max(PullFilter* mp, int len, uint8** data_p, uint8* tmpbuf);
  void pullf_free(PullFilter* mp);
  int pullf_read_fixed(PullFilter* src, int len, uint8* dst);
  
  int pullf_create_mbuf_reader(PullFilter** pf_p, MBuf* mbuf);
  
  #define GETBYTE(pf, dst)                           \
      do {                                           \
          uint8 __b;                                 \
          int __res = pullf_read_fixed(pf, 1, &__b); \
          if (__res < 0)                             \
              return __res;                          \
          (dst) = __b;                               \
      } while (0)
  
  #endif /* __PX_MBUF_H */
  