lzrw3.h

linux-2.6.15.6

#ifndef _LZRW3_H
#define _LZRW3_H
/*
 * $Source: /homes/cvs/ftape-stacked/ftape/compressor/lzrw3.h,v $
 * $Revision: 1.1 $
 * $Date: 1997/10/05 19:12:30 $
 *
 *  include files for lzrw3. Only slighty modified from the original
 *  version. Assembles the three include files compress.h, port.h and
 *  fastcopy.h from the original lzrw3 package.
 *
 */

#include <linux/types.h>
#include <linux/string.h>

/******************************************************************************/
/*                                                                            */
/*                                 COMPRESS.H                                 */
/*                                                                            */
/******************************************************************************/
/*                                                                            */
/* Author : Ross Williams.                                                    */
/* Date   : December 1989.                                                    */
/*                                                                            */
/* This header file defines the interface to a set of functions called        */
/* 'compress', each member of which implements a particular data compression  */
/* algorithm.                                                                 */
/*                                                                            */
/* Normally in C programming, for each .H file, there is a corresponding .C   */
/* file that implements the functions promised in the .H file.                */
/* Here, there are many .C files corresponding to this header file.           */
/* Each comforming implementation file contains a single function             */
/* called 'compress' that implements a single data compression                */
/* algorithm that conforms with the interface specified in this header file.  */
/* Only one algorithm can be linked in at a time in this organization.        */
/*                                                                            */
/******************************************************************************/
/*                                                                            */
/*                    DEFINITION OF FUNCTION COMPRESS                         */
/*                    ===============================                         */
/*                                                                            */
/* Summary of Function Compress                                               */
/* ----------------------------                                               */
/* The action that 'compress' takes depends on its first argument called      */
/* 'action'.  The function provides three actions:                            */
/*                                                                            */
/*    - Return information about the algorithm.                               */
/*    - Compress   a block of memory.                                         */
/*    - Decompress a block of memory.                                         */
/*                                                                            */
/* Parameters                                                                 */
/* ----------                                                                 */
/* See the formal C definition later for a description of the parameters.     */
/*                                                                            */
/* Constants                                                                  */
/* ---------                                                                  */
/* COMPRESS_OVERRUN: The constant COMPRESS_OVERRUN defines by how many bytes  */
/* an algorithm is allowed to expand a block during a compression operation.  */
/*                                                                            */
/* Although compression algorithms usually compress data, there will always   */
/* be data that a given compressor will expand (this can be proven).          */
/* Fortunately, the degree of expansion can be limited to a single bit, by    */
/* copying over the input data if the data gets bigger during compression.    */
/* To allow for this possibility, the first bit of a compressed               */
/* representation can be used as a flag indicating whether the                */
/* input data was copied over, or truly compressed. In practice, the first    */
/* byte would be used to store this bit so as to maintain byte alignment.     */
/*                                                                            */
/* Unfortunately, in general, the only way to tell if an algorithm will       */
/* expand a particular block of data is to run the algorithm on the data.     */
/* If the algorithm does not continuously monitor how many output bytes it    */
/* has written, it might write an output block far larger than the input      */
/* block before realizing that it has done so.                                */
/* On the other hand, continuous checks on output length are inefficient.     */
/*                                                                            */
/* To cater for all these problems, this interface definition:                */
/* > Allows a compression algorithm to return an output block that is up to   */
/*   COMPRESS_OVERRUN bytes longer than the input block.                      */
/* > Allows a compression algorithm to write up to COMPRESS_OVERRUN bytes     */
/*   more than the length of the input block to the memory of the output      */
/*   block regardless of the length of the output block eventually returned.  */
/*   This allows an algorithm to overrun the length of the input block in the */
/*   output block by up to COMPRESS_OVERRUN bytes between expansion checks.   */
/*                                                                            */
/* The problem does not arise for decompression.                              */
/*                                                                            */
/* Identity Action                                                            */
/* ---------------                                                            */
/* > action must be COMPRESS_ACTION_IDENTITY.                                 */
/* > p_dst_len must point to a longword to receive a longword address.        */
/* > The value of the other parameters does not matter.                       */
/* > After execution, the longword that p_dst_len points to will be a pointer */
/*   to a structure of type compress_identity.                                */
/*   Thus, for example, after the call, (*p_dst_len)->memory will return the  */
/*   number of bytes of working memory that the algorithm requires to run.    */
/* > The values of the identity structure returned are fixed constant         */
/*   attributes of the algorithm and must not vary from call to call.         */
/*                                                                            */
/* Common Requirements for Compression and Decompression Actions              */
/* -------------------------------------------------------------              */
/* > wrk_mem must point to an unused block of memory of a length specified in */
/*   the algorithm's identity block. The identity block can be obtained by    */
/*   making a separate call to compress, specifying the identity action.      */
/* > The INPUT BLOCK is defined to be Memory[src_addr,src_addr+src_len-1].    */
/* > dst_len will be used to denote *p_dst_len.                               */
/* > dst_len is not read by compress, only written.                           */
/* > The value of dst_len is defined only upon termination.                   */
/* > The OUTPUT BLOCK is defined to be Memory[dst_addr,dst_addr+dst_len-1].   */
/*                                                                            */
/* Compression Action                                                         */
/* ------------------                                                         */
/* > action must be COMPRESS_ACTION_COMPRESS.                                 */
/* > src_len must be in the range [0,COMPRESS_MAX_ORG].                       */
/* > The OUTPUT ZONE is defined to be                                         */
/*      Memory[dst_addr,dst_addr+src_len-1+COMPRESS_OVERRUN].                 */
/* > The function can modify any part of the output zone regardless of the    */
/*   final length of the output block.                                        */
/* > The input block and the output zone must not overlap.                    */
/* > dst_len will be in the range [0,src_len+COMPRESS_OVERRUN].               */
/* > dst_len will be in the range [0,COMPRESS_MAX_COM] (from prev fact).      */
/* > The output block will consist of a representation of the input block.    */
/*                                                                            */
/* Decompression Action                                                       */
/* --------------------                                                       */
/* > action must be COMPRESS_ACTION_DECOMPRESS.                               */
/* > The input block must be the result of an earlier compression operation.  */