1 line
15 KiB
C
Executable File
1 line
15 KiB
C
Executable File
LZRW HEADER FILES
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=================
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Author : Ross Williams.
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Date : 25-Jun-1991.
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1. This file contains two header files used by the LZRW series data
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compression algorithms:
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compress.h - The header file for the algorithms.
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port.h - Contains portability definitions.
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2. This code is public domain.
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3. port.h is included only as an example. Please ensure that your
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own definitions for these macros are correct.
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UPDATED
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=======
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Author : Matt Slot, Ambrosia Software.
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Date : 18-Jan-2007.
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Added dst_max field, routine now returns -1 instead of writing past buffer.
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This change is also public domain.
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/******************************************************************************/
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/* */
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/* COMPRESS.H */
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/* */
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/******************************************************************************/
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/* */
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/* Author : Ross Williams. */
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/* Date : December 1989. */
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/* */
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/* This header file defines the interface to a set of functions called */
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/* 'compress', each member of which implements a particular data compression */
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/* algorithm. */
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/* */
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/* Normally in C programming, for each .H file, there is a corresponding .C */
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/* file that implements the functions promised in the .H file. */
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/* Here, there are many .C files corresponding to this header file. */
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/* Each comforming implementation file contains a single function */
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/* called 'compress' that implements a single data compression */
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/* algorithm that conforms with the interface specified in this header file. */
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/* Only one algorithm can be linked in at a time in this organization. */
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/* */
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/******************************************************************************/
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/* */
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/* DEFINITION OF FUNCTION COMPRESS */
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/* =============================== */
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/* */
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/* Summary of Function Compress */
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/* ---------------------------- */
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/* The action that 'compress' takes depends on its first argument called */
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/* 'action'. The function provides three actions: */
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/* */
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/* - Return information about the algorithm. */
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/* - Compress a block of memory. */
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/* - Decompress a block of memory. */
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/* */
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/* Parameters */
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/* ---------- */
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/* See the formal C definition later for a description of the parameters. */
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/* */
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/* Constants */
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/* --------- */
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/* COMPRESS_OVERRUN: The constant COMPRESS_OVERRUN defines by how many bytes */
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/* an algorithm is allowed to expand a block during a compression operation. */
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/* */
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/* Although compression algorithms usually compress data, there will always */
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/* be data that a given compressor will expand (this can be proven). */
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/* Fortunately, the degree of expansion can be limited to a single bit, by */
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/* copying over the input data if the data gets bigger during compression. */
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/* To allow for this possibility, the first bit of a compressed */
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/* representation can be used as a flag indicating whether the */
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/* input data was copied over, or truly compressed. In practice, the first */
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/* byte would be used to store this bit so as to maintain byte alignment. */
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/* */
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/* Unfortunately, in general, the only way to tell if an algorithm will */
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/* expand a particular block of data is to run the algorithm on the data. */
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/* If the algorithm does not continuously monitor how many output bytes it */
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/* has written, it might write an output block far larger than the input */
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/* block before realizing that it has done so. */
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/* On the other hand, continuous checks on output length are inefficient. */
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/* */
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/* To cater for all these problems, this interface definition: */
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/* > Allows a compression algorithm to return an output block that is up to */
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/* COMPRESS_OVERRUN bytes longer than the input block. */
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/* > Allows a compression algorithm to write up to COMPRESS_OVERRUN bytes */
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/* more than the length of the input block to the memory of the output */
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/* block regardless of the length of the output block eventually returned. */
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/* This allows an algorithm to overrun the length of the input block in the */
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/* output block by up to COMPRESS_OVERRUN bytes between expansion checks. */
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/* */
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/* The problem does not arise for decompression. */
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/* */
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/* Identity Action */
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/* --------------- */
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/* > action must be COMPRESS_ACTION_IDENTITY. */
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/* > p_dst_len must point to a longword to receive a longword address. */
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/* > The value of the other parameters does not matter. */
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/* > After execution, the longword that p_dst_len points to will be a pointer */
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/* to a structure of type compress_identity. */
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/* Thus, for example, after the call, (*p_dst_len)->memory will return the */
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/* number of bytes of working memory that the algorithm requires to run. */
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/* > The values of the identity structure returned are fixed constant */
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/* attributes of the algorithm and must not vary from call to call. */
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/* */
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/* Common Requirements for Compression and Decompression Actions */
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/* ------------------------------------------------------------- */
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/* > wrk_mem must point to an unused block of memory of a length specified in */
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/* the algorithm's identity block. The identity block can be obtained by */
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/* making a separate call to compress, specifying the identity action. */
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/* > The INPUT BLOCK is defined to be Memory[src_addr,src_addr+src_len-1]. */
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/* > dst_len will be used to denote *p_dst_len. */
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/* > dst_len is not read by compress, only written. */
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/* > The value of dst_len is defined only upon termination. */
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/* > The OUTPUT BLOCK is defined to be Memory[dst_addr,dst_addr+dst_len-1]. */
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/* */
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/* Compression Action */
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/* ------------------ */
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/* > action must be COMPRESS_ACTION_COMPRESS. */
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/* > src_len must be in the range [0,COMPRESS_MAX_ORG]. */
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/* > The OUTPUT ZONE is defined to be */
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/* Memory[dst_addr,dst_addr+src_len-1+COMPRESS_OVERRUN]. */
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/* > The function can modify any part of the output zone regardless of the */
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/* final length of the output block. */
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/* > The input block and the output zone must not overlap. */
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/* > dst_len will be in the range [0,src_len+COMPRESS_OVERRUN]. */
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/* > dst_len will be in the range [0,COMPRESS_MAX_COM] (from prev fact). */
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/* > The output block will consist of a representation of the input block. */
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/* */
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/* Decompression Action */
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/* -------------------- */
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/* > action must be COMPRESS_ACTION_DECOMPRESS. */
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/* > The input block must be the result of an earlier compression operation. */
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/* > If the previous fact is true, the following facts must also be true: */
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/* > src_len will be in the range [0,COMPRESS_MAX_COM]. */
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/* > dst_len will be in the range [0,COMPRESS_MAX_ORG]. */
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/* > The input and output blocks must not overlap. */
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/* > Only the output block is modified. */
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/* > Upon termination, the output block will consist of the bytes contained */
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/* in the input block passed to the earlier compression operation. */
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/* */
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/******************************************************************************/
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#include "port.h"
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#define COMPRESS_ACTION_IDENTITY 0
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#define COMPRESS_ACTION_COMPRESS 1
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#define COMPRESS_ACTION_DECOMPRESS 2
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#define COMPRESS_OVERRUN 1024
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#define COMPRESS_MAX_COM 0x70000000
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#define COMPRESS_MAX_ORG (COMPRESS_MAX_COM-COMPRESS_OVERRUN)
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#define COMPRESS_MAX_STRLEN 255
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/* The following structure provides information about the algorithm. */
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/* > The top bit of id must be zero. The remaining bits must be chosen by */
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/* the author of the algorithm by tossing a coin 31 times. */
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/* > The amount of memory requested by the algorithm is specified in bytes */
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/* and must be in the range [0,0x70000000]. */
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/* > All strings s must be such that strlen(s)<=COMPRESS_MAX_STRLEN. */
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struct compress_identity
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{
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ULONG id; /* Identifying number of algorithm. */
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ULONG memory; /* Number of bytes of working memory required. */
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char *name; /* Name of algorithm. */
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char *version; /* Version number. */
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char *date; /* Date of release of this version. */
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char *copyright; /* Copyright message. */
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char *author; /* Author of algorithm. */
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char *affiliation; /* Affiliation of author. */
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char *vendor; /* Where the algorithm can be obtained. */
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};
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int compress( /* Single function interface to compression algorithm. */
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UWORD action, /* Action to be performed. */
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UBYTE *wrk_mem, /* Working memory temporarily given to routine to use. */
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UBYTE *src_adr, /* Address of input data. */
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ULONG src_len, /* Length of input data. */
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ULONG dst_max, /* Allocated length of output buffer. */
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UBYTE *dst_adr, /* Address of output data. */
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ULONG *p_dst_len /* Pointer to a longword where routine will write: */
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/* If action=..IDENTITY => Adr of id structure. */
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/* If action=..COMPRESS => Length of output data. */
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/* If action=..DECOMPRESS => Length of output data. */
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);
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/******************************************************************************/
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/* End of COMPRESS.H */
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/******************************************************************************/
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/******************************************************************************/
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/* */
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/* PORT.H */
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/* */
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/******************************************************************************/
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/* */
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/* This module contains macro definitions and types that are likely to */
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/* change between computers. */
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/* */
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/******************************************************************************/
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#ifndef DONE_PORT /* Only do this if not previously done. */
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#ifdef THINK_C
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#define UBYTE unsigned char /* Unsigned byte */
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#define UWORD unsigned int /* Unsigned word (2 bytes) */
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#define ULONG unsigned long /* Unsigned word (4 bytes) */
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#define BOOL unsigned char /* Boolean */
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#define FOPEN_BINARY_READ "rb" /* Mode string for binary reading. */
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#define FOPEN_BINARY_WRITE "wb" /* Mode string for binary writing. */
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#define FOPEN_TEXT_APPEND "a" /* Mode string for text appending. */
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#define REAL double /* USed for floating point stuff. */
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#endif
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#define DONE_PORT /* Don't do all this again. */
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#define MALLOC_FAIL NULL /* Failure status from malloc() */
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#define LOCAL static /* For non-exported routines. */
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#define EXPORT /* Signals exported function. */
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#define then /* Useful for aligning ifs. */
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#endif
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/******************************************************************************/
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/* End of PORT.H */
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/******************************************************************************/
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