DESCRIPTION
-----------
This archive contains a simple and readable ANSI C implementation of
Arithmetic coding and decoding.  This implementation is not intended to be
the best, fastest, smallest, or any other performance related adjective.

More information on Arithmetic encoding may be found at:
https://michaeldipperstein.github.io/arithmetic.html

FILES
-----
arcode.c        - Library of Arithmetic encoding and decoding routines.
arcode.h        - Header containing prototypes for library functions.
COPYING         - Rules for copying and distributing LGPL software
LICENSE         - GNU Lesser General Public License
Makefile        - makefile for this project (assumes gcc compiler and GNU make)
README          - this file
sample.c        - Demonstration of how to use Arithmetic library functions
optlist/        - Subtree containing optlist command line option parser library
bitfile/        - Subtree containing bitfile bitwise file library

BUILDING
--------
To build these files with GNU make and gcc:
1. Windows users should define the environment variable OS to be Windows or
   Windows_NT.  This is often already done.
2. Enter the command "make" from the command line or "make DEBUG=1" to compile
   with debug options.

The executable will be named sample (or sample.exe).

GIT NOTE: Updates to subtrees optlist and bitfile don't get pulled by "git pull"
Use the following commands to pull their updates:
git subtree pull --prefix optlist https://github.com/MichaelDipperstein/optlist.git master --squash
git subtree pull --prefix bitfile https://github.com/MichaelDipperstein/bitfile.git master --squash

USAGE
-----
Usage: sample <options>

options:
  -c : Encode input file to output file.
  -d : Decode input file to output file.
  -i <filename> : Name of input file.
  -o <filename> : Name of output file.
  -a : Use adaptive model instead of static.
  -h|?  : Print out command line options.

-a      Compress/decompress using the adaptive model.  Data compressed using
        the adaptive model must be decompressed using the adaptive model.

-c      Generate a probability range list for the specified input file
        (see -i) and use arithmetic coding compresses the file to the
        specified output file (see -o).

-d      Decompresses the specified input file (see -i) writing the results to
        the specified output file (see -o).  Only files compressed by this
        program may be decompressed.

-i <filename>   The name of the input file.  There is no valid usage of this
                program without a specified input file.

-o <filename>   The name of the output file.  If no file is specified, stdout
                will be used.  NOTE: Sending compressed output to stdout may
                produce undesirable results.

LIBRARY API
-----------
Encoding Data:
int ArEncodeFile(FILE *inFile, FILE *outFile, const model_t model);
inFile
    The file stream to be encoded.  It must be opened and it must also be
    rewindable if a static model is used.  If NULL, stdin will be used.
outFile
    The file stream receiving the encoded results.  It must be opened as binary.
    If NULL, stdout will be used.
model
    model_t type value indicating whether a static model or a dynamic model is
    to be used.
Return Value
    Non-zero for success, zero for failure.

Decoding Data:
int ArDecodeFile(FILE *inFile, FILE *outFile, const model_t model);
inFile
    The file stream containing the encoded input.  It must be opened as binary.
    If NULL, stdin will be used.
outFile
    The file stream receiving the decoded results.  It must be opened as binary.
    If NULL, stdout will be used.
model
    model_t type value indicating whether a static model or a dynamic model is
    to be used.
Return Value
    Zero for success, non-zero for failure.

HISTORY
-------
04/01/04  - Initial Release
08/13/04  - Added support for adaptive encoding
06/21/05  - Corrected BitFileGetBits/PutBits error that accessed an extra
            byte when given an integral number of bytes.
01/11/06  - Uses BitFileGetBitsIntBit and FilePutBitsInt for reading and
            writing the header.
            - This makes the code a little cleaner, but the new header is not
              compatible with the old header.
03/17/14  - Changed the API so that encode and decode routines accept opened
            file streams instead of file names.
          - Eliminated all global variables.
10/26/14  - Upgrade to latest Bitfile and Oplist Libraries
          - Tighter adherence to Michael Barr's "Top 10 Bug-Killing Coding
            Standard Rules" (http://www.barrgroup.com/webinars/10rules).
07/15/17  - Changes for easier use with GitHub
09/19/19  - Updated e-mail address
          - Updated optlist and bitfile subtrees

TODO
----
- Add support for higher order models.
- Provide dynamic link library (DLL) example.

AUTHOR
------
Michael Dipperstein (mdipperstein@gmail.com)