#ifndef rangecod_h #define rangecod_h /* rangecod.h headerfile for range encoding (c) Michael Schindler 1997, 1998, 1999 http://www.compressconsult.com/ or http://eiunix.tuwien.ac.at/~michael michael@compressconsult.com michael@eiunix.tuwien.ac.at This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. It may be that this program violates local patents in your country, however it is belived (NO WARRANTY!) to be patent-free here in Austria. Glen Langdon also confirmed my poinion that IBM UK did not protect that method. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. Range encoding is based on an article by G.N.N. Martin, submitted March 1979 and presented on the Video & Data Recording Conference, Southampton, July 24-27, 1979. If anyone can name the original copyright holder of that article or locate G.N.N. Martin please contact me; this might allow me to make that article available on the net for general public. Range coding is closely related to arithmetic coding, except that it does renormalisation in larger units than bits and is thus faster. An earlier version of this code was distributed as byte oriented arithmetic coding, but then I had no knowledge of Martin's paper from seventy-nine. The input and output is done by the INBYTE and OUTBYTE macros defined in the .c file; change them as needed; the first parameter passed to them is a pointer to the rangecoder structure; extend that structure as needed (and don't forget to initialize the values in start_encoding resp. start_decoding). This distribution writes to stdout and reads from stdin. There are no global or static var's, so if the IO is thread save the whole rangecoder is - unless GLOBALRANGECODER is defined. For error recovery the last 3 bytes written contain the total number of bytes written since starting the encoder. This can be used to locate the beginning of a block if you have only the end. For some application using a global coder variable may provide a better performance. This will allow you to use only one coder at a time and will destroy thread savety. To enabble this feature uncomment the #define GLOBALRANGECODER line below. */ #define GLOBALRANGECODER #include "port.h" #if 0 /* done in port.h */ #include #if INT_MAX > 0xffff typedef unsigned int uint4; typedef unsigned short uint2; #else typedef unsigned long uint4; typedef unsigned int uint2; #endif #endif extern char coderversion[]; typedef uint4 code_value; /* Type of an rangecode value */ /* must accomodate 32 bits */ /* it is highly recommended that the total frequency count is less */ /* than 1 << 19 to minimize rounding effects. */ /* the total frequency count MUST be less than 1<<23 */ typedef uint4 freq; /* make the following private in the arithcoder object in C++ */ typedef struct { uint4 low, /* low end of interval */ range, /* length of interval */ help; /* bytes_to_follow resp. intermediate value */ unsigned char buffer;/* buffer for input/output */ /* the following is used only when encoding */ uint4 bytecount; /* counter for outputed bytes */ /* insert fields you need for input/output below this line! */ } rangecoder; /* supply the following as methods of the arithcoder object */ /* omit the first parameter then (C++) */ #ifdef GLOBALRANGECODER #define start_encoding(rc,a,b) M_start_encoding(a,b) #define encode_freq(rc,a,b,c) M_encode_freq(a,b,c) #define encode_shift(rc,a,b,c) M_encode_shift(a,b,c) #define done_encoding(rc) M_done_encoding() #define start_decoding(rc) M_start_decoding() #define decode_culfreq(rc,a) M_decode_culfreq(a) #define decode_culshift(rc,a) M_decode_culshift(a) #define decode_update(rc,a,b,c) M_decode_update(a,b,c) #define decode_byte(rc) M_decode_byte() #define decode_short(rc) M_decode_short() #define done_decoding(rc) M_done_decoding() #endif /* Start the encoder */ /* rc is the range coder to be used */ /* c is written as first byte in the datastream (header,...) */ void start_encoding( rangecoder *rc, char c, int initlength); /* Encode a symbol using frequencies */ /* rc is the range coder to be used */ /* sy_f is the interval length (frequency of the symbol) */ /* lt_f is the lower end (frequency sum of < symbols) */ /* tot_f is the total interval length (total frequency sum) */ /* or (a lot faster): tot_f = 1<