jsphmrrw / huffman Goto Github PK

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

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

FILES
-----
canonical.c     - Huffman encoding and decoding routines using canonical codes
COPYING         - Rules for copying and distributing GPL software
COPYING.LESSER  - Rules for copying and distributing LGPL software
huffman.c       - Huffman encoding and decoding routines
huffman.h       - Header file used by code calling library functions
huflocal.h      - Header file with internal library definitions common to both
                  canonical and conventional techniques
huflocal.c      - File with internal library functions common to both canonical
                  and conventional techniques
Makefile        - makefile for this project (assumes gcc compiler and GNU make)
README          - this file
sample.c        - Demonstration of how to use Huffman library functions
optlist/        - Subtree containing optlist command line option parser library
bitfile/        - Subtree containing bitfile bitwise file library
bitarray/       - Subtree containing bitarray bitwise array library

BUILDING
--------
To build these files with GNU make and gcc, simply enter "make" from the
command line.

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

options:
  -C : Encode/Decode using a canonical code.
  -c : Encode input file to output file.
  -d : Decode input file to output file.
  -t : Generate code tree for input file to output file.
  -i <filename> : Name of input file.
  -o <filename> : Name of output file.
  -h|?  : Print out command line options.

-C      Uses a canonical Huffman code (canonical.c).

-c      Generates a Huffman tree for the specified input file (see -i) and
        compresses a file using the tree 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.

-t      Generates a Huffman tree for the specified input file (see -i) and
        writes the resulting code to the specified output file (see -o).

-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 (Traditional or Canonical codes):
int HuffmanEncodeFile(FILE *inFile, FILE *outFile);
int CanonicalEncodeFile(FILE *inFile, FILE *outFile);
inFile
    The file stream to be encoded.  It must be rewindable and opened.
    NULL pointers will return an error.
outFile
    The file stream receiving the encoded results.  It must be opened.  NULL
    pointers will return an error.
Return Value
    Zero for success, -1 for failure.  Error type is contained in errno.  Files
    will remain open.

Decoding Data (Traditional or Canonical codes):
int HuffmanDecodeFile(FILE *inFile, FILE *outFile);
int CanonicalDecodeFile(FILE *inFile, FILE *outFile);
inFile
    The file stream to be decoded.  It must be opened.  NULL pointers will
    return an error.
outFile
    The file stream receiving the decoded results.  It must be opened.  NULL
    pointers will return an error.
Return Value
    Zero for success, -1 for failure.  Error type is contained in errno.  Files
    will remain open.


Displaying a Tree Generated by Algorithm (Traditional or Canonical codes):
int HuffmanShowTree(FILE *inFile, FILE *outFile);
int CanonicalShowTree(FILE *inFile, FILE *outFile);
inFile
    The file stream that a tree will be generated for.  It must be opened.
    NULL pointers will return an error.
outFile
    The file stream that the tree will be sent to.  It must be opened.  NULL
    pointers will return an error.  It is perfectly acceptable to use stdout.
Return Value
    Zero for success, -1 for failure.  Error type is contained in errno.  Files
    will remain open.

HISTORY
-------
10/23/03  - Corrected errors which occurred when encoding and decoding files
            containing a single symbol.
          - Modified canonical version to dynamically allocate the array used
            to store the canonical list of codes.
          - Use $(OS) environment variable to determine operating system in
            Makefile.
11/20/03  - Correctly handle symbol codes that are over 16 bits long.  These
            changes can handle codes up to 255 bits long.
01/05/04  - Encode EOF along with other symbols
01/12/04  - Use bit stream file library
02/02/04  - Use bit array library
02/25/04  - Make huffman.c and chuffman.c more library like by removing main
            and adding a header file with prototypes for encode/decode
            functions.
          - Add sample usage of functions.
06/14/04  - Use latest version of bitfile.c.
          - Make routines local to huffman.c and chuffman.c static so that
            they may be called from the same program.
          - Include use of canonical and traditional Huffman codes in
            sample program.
05/22/05  - Provides single declaration for items common canonical and
            traditional encoding source
          - Makefile builds libraries for easier LGPL compliance.
06/21/05  - Corrected BitFileGetBits/PutBits error that accessed an extra
            byte when given an integral number of bytes.
08/29/07  - Explicitly licensed under LGPL version 3.
          - Replaces getopt() with optlist library.
06/08/08  - Incorporates Emanuele Giaquinta's patch to eliminate redundant
            check during the canonical decode process.
08/24/14  - Restructured code for cleaner Traditional/Canonical separation
11/18/14  - Changed the API so that encode and decode routines accept opened
            file streams instead of file names.
          - Changed return value to 0 for success and -1 for failure with
            reason in errno.
          - Upgraded to latest oplist and bitfile libraries.
          - Tighter adherence to Michael Barr's "Top 10 Bug-Killing Coding
            Standard Rules" (http://www.barrgroup.com/webinars/10rules).
07/16/17  - Changes for easier use with GitHub

TODO
----
- Provide a command line option to change symbol size.
- Implement bijective scheme for ending file on byte boundary without
  counting the number of encoded symbols encoded (http://bijective.dogma.net/).

AUTHOR
------
Michael Dipperstein ([email protected])
https://michaeldipperstein.github.io