/usr/include/hdf/crle.h is in libhdf4-alt-dev 4.2.13-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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* 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: crle.h
* Purpose: Header file for run-length encoding information.
* Dependencies: should only be included from hcompi.h
* Invokes: none
* Contents: Structures & definitions for run-length encoding. This header
* should only be included in hcomp.c and crle.c.
* Structure definitions:
* Constant definitions:
*---------------------------------------------------------------------------*/
/* avoid re-inclusion */
#ifndef __CRLE_H
#define __CRLE_H
#if defined c_plusplus || defined __cplusplus
extern "C"
{
#endif /* c_plusplus || __cplusplus */
/*
** from crle.c
*/
extern int32 HCPcrle_stread
(accrec_t * rec);
extern int32 HCPcrle_stwrite
(accrec_t * rec);
extern int32 HCPcrle_seek
(accrec_t * access_rec, int32 offset, int origin);
extern int32 HCPcrle_inquire
(accrec_t * access_rec, int32 *pfile_id, uint16 *ptag, uint16 *pref,
int32 *plength, int32 *poffset, int32 *pposn, int16 *paccess,
int16 *pspecial);
extern int32 HCPcrle_read
(accrec_t * access_rec, int32 length, void * data);
extern int32 HCPcrle_write
(accrec_t * access_rec, int32 length, const void * data);
extern intn HCPcrle_endaccess
(accrec_t * access_rec);
#if defined c_plusplus || defined __cplusplus
}
#endif /* c_plusplus || __cplusplus */
/* size of the RLE buffer */
#define RLE_BUF_SIZE 128
/* NIL code for run bytes */
#define RLE_NIL (-1)
/* minimum length of run */
#define RLE_MIN_RUN 3
/* maximum length of run */
#define RLE_MAX_RUN (RLE_BUF_SIZE+RLE_MIN_RUN-1)
/* minimum length of mix */
#define RLE_MIN_MIX 1
/*
* Notes on RLE_MIN_RUN and RLE_MIN_MIX:
* (excerpt from QAK's email to RA - see bug HDFFR-1261)
*
* These are [small] optimizations for improving the compression ratio. The
* algorithm won't encode a run of identical bytes unless it's at least
* RLE_MIN_RUN bytes long. So, we can assume that all runs are at least
* that many bytes, and subtract RLE_MIN_RUN from the actual run length,
* allowing encoding of runs that are a little bit longer than otherwise
* allowed (i.e. runs up to 127+RLE_MIN_RUN bytes, instead of only 127 bytes).
* Similarly for RLE_MIN_MIX - there must be at least RLE_MIN_MIX bytes in a
* "mixed" sequence of bytes, so we can encode a little bit longer sequence
* of mixed bytes (127+RLE_MIN_MIX bytes, instead of only 127 bytes).
*/
/* RLE [en|de]coding information */
typedef struct
{
int32 offset; /* offset in the file */
uint8 buffer[RLE_BUF_SIZE]; /* buffer for storing RLE bytes */
intn buf_length; /* number of bytes in buffer */
intn buf_pos; /* offset into the buffer */
uintn last_byte, /* the last byte stored in the buffer */
second_byte; /* the second to last byte stored in the buffer */
enum
{
RLE_INIT, /* initial state, need to read a byte to
determine the next state */
RLE_RUN, /* buffer up to the current position is a run */
RLE_MIX /* buffer up to the current position is a mix */
}
rle_state; /* state of the buffer storage */
}
comp_coder_rle_info_t;
#ifndef CRLE_MASTER
extern funclist_t crle_funcs; /* functions to perform run-length encoding */
#else
funclist_t crle_funcs =
{ /* functions to perform run-length encoding */
HCPcrle_stread,
HCPcrle_stwrite,
HCPcrle_seek,
HCPcrle_inquire,
HCPcrle_read,
HCPcrle_write,
HCPcrle_endaccess
};
#endif
#endif /* __CRLE_H */
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