cnbit.h

Go to the documentation of this file.

/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 * Copyright by The HDF Group.                                               *
 * Copyright by the Board of Trustees of the University of Illinois.         *
 * All rights reserved.                                                      *
 *                                                                           *
 * This file is part of HDF.  The full HDF copyright notice, including       *
 * terms governing use, modification, and redistribution, is contained in    *
 * the COPYING file, which can be found at the root of the source code       *
 * distribution tree, or in https://support.hdfgroup.org/ftp/HDF/releases/.  *
 * If you do not have access to either file, you may request a copy from     *
 * help@hdfgroup.org.                                                        *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

 /* $Id$ */

 /*-----------------------------------------------------------------------------
 * File:    cnbit.h
 * Purpose: Header file for N-bit encoding information.
 * Dependencies: should only be included from hcompi.h
 * Invokes: none
 * Contents: Structures & definitions for N-bit encoding.
 * Structure definitions:
 * Constant definitions:
 *---------------------------------------------------------------------------*/

/* avoid re-inclusion */
#ifndef __CNBIT_H
#define __CNBIT_H

#if defined c_plusplus || defined __cplusplus
extern      "C"
{
#endif                          /* c_plusplus || __cplusplus */

/*
   ** from cnbit.c
 */

    extern int32 HCPcnbit_stread
                (accrec_t * rec);

    extern int32 HCPcnbit_stwrite
                (accrec_t * rec);

    extern int32 HCPcnbit_seek
                (accrec_t * access_rec, int32 offset, int origin);

    extern int32 HCPcnbit_inquire
                (accrec_t * access_rec, int32 *pfile_id, uint16 *ptag, uint16 *pref,
               int32 *plength, int32 *poffset, int32 *pposn, int16 *paccess,
                 int16 *pspecial);

    extern int32 HCPcnbit_read
                (accrec_t * access_rec, int32 length, void * data);

    extern int32 HCPcnbit_write
                (accrec_t * access_rec, int32 length, const void * data);

    extern intn HCPcnbit_endaccess
                (accrec_t * access_rec);

#if defined c_plusplus || defined __cplusplus
}
#endif                          /* c_plusplus || __cplusplus */

/* size of the N-bit buffer */
#define NBIT_BUF_SIZE   (MAX_NT_SIZE*64)
/* size of the N-bit mask buffer (same as buffer size for now) */
#define NBIT_MASK_SIZE  (MAX_NT_SIZE)

typedef struct
{                               /* structure to hold bit vector info */
    intn        offset,         /* offset of the bit information */
                length;         /* number of bits in the information */
    uint8       mask;           /* mask for this bit vector */
}
nbit_mask_info_t;

/* N-bit [en|de]coding information */
typedef struct
  {
      int32       nt;           /* number type of data we are encoding */
      intn        nt_size;      /* size of the number-type in the file */
      intn        fill_one;     /* whether to fill with 1's or not (0's) */
      intn        sign_ext;     /* whether to sign extend or not */
      uint8       buffer[NBIT_BUF_SIZE];    /* buffer for expanding n-bit data in */
      intn        buf_pos;      /* current offset in the expansion buffer */
      intn        mask_off,     /* offset of the bit to start masking with */
                  mask_len;     /* number of bits to mask */
      int32       offset;       /* offset in the file in terms of bytes */
      uint8       mask_buf[NBIT_MASK_SIZE];     /* buffer to hold the bitmask */
      nbit_mask_info_t mask_info[NBIT_MASK_SIZE];   /* information about the mask */
      intn        nt_pos;       /* current byte to read or write */
  }
comp_coder_nbit_info_t;

#ifndef CNBIT_MASTER
extern funclist_t cnbit_funcs;  /* functions to perform N-bit encoding */
#else
funclist_t  cnbit_funcs =
{                               /* functions to perform N-bit encoding */
    HCPcnbit_stread,
    HCPcnbit_stwrite,
    HCPcnbit_seek,
    HCPcnbit_inquire,
    HCPcnbit_read,
    HCPcnbit_write,
    HCPcnbit_endaccess
};
#endif

#endif /* __CNBIT_H */