compressing a buffer

This is a discussion on compressing a buffer within the C Programming forums, part of the General Programming Boards category; Hello, I have a buffer and I want to compress the contents of the buffer. And also be able to ...

  1. #1
    UK2
    Join Date
    Sep 2003
    Posts
    112

    compressing a buffer

    Hello,

    I have a buffer and I want to compress the contents of the buffer. And also be able to decompress.

    Can anyone point me in the right direction where I can find out more information on how to do this?

    Many thanks,

    Steve

  2. #2
    Kernel hacker
    Join Date
    Jul 2007
    Location
    Farncombe, Surrey, England
    Posts
    15,677
    There are many different sorts of compressions:
    - Huffman coding (use shorter bitpatterns for the most common datasets, longer for the rarer ones). You can either use a dynamic approach, where the bitpatterns and their translation is generated based on the current data, and a translation table stored in the compressed data. The other altiernative, which relies on statistical knowledge of the data, uses a fixed set of translation table, where the (statistically) most common occurances use the shortest bitpatterns.
    - RLE - Run length encoding (AAAAAB turns into 5(A)B)
    - Byte Pair Compression - Take a block of data, find an unused byte-value, encode the most common two bytes of data in the block as that unused byte-value. Repeat until no further compression is possible for this block.

    Of course, if you want to make it simple, just write the data out to a file or pipe, and run that through for example gzip...

    --
    Mats
    Compilers can produce warnings - make the compiler programmers happy: Use them!
    Please don't PM me for help - and no, I don't do help over instant messengers.

  3. #3
    Registered User whiteflags's Avatar
    Join Date
    Apr 2006
    Location
    United States
    Posts
    7,655
    Here's one compression algorithm. That's also a very good search term to plug into clusty or google.

    cprogramming.com wrote an article about this subject: http://cprogramming.com/tutorial/com...y/huffman.html

  4. #4
    uint64_t...think positive xuftugulus's Avatar
    Join Date
    Feb 2008
    Location
    Pacem
    Posts
    355
    Yes indeed it is a good search term. Huffman trees are widely used in many compression programs mainly because of the decompression speed. Arithmetic encoding is another obscure way to compress, but not recommended as a starting attempt.
    Taking a look at wikipedia one can find the most common algorithms nicely explained. I impleented huffman using only wiki reference.
    Code:
    ...
        goto johny_walker_red_label;
    johny_walker_blue_label: exit(-149$);
    johny_walker_red_label : exit( -22$);
    A typical example of ...cheap programming practices.

  5. #5
    Captain Crash brewbuck's Avatar
    Join Date
    Mar 2007
    Location
    Portland, OR
    Posts
    7,239
    zlib.

    Rolling your own will take months, and it will do worse than zlib.

  6. #6
    Algorithm Dissector iMalc's Avatar
    Join Date
    Dec 2005
    Location
    New Zealand
    Posts
    6,299
    Quote Originally Posted by steve1_rm View Post
    Hello,

    I have a buffer and I want to compress the contents of the buffer. And also be able to decompress.

    Can anyone point me in the right direction where I can find out more information on how to do this?

    Many thanks,

    Steve
    Waaay too little information I'm afraid. Here's a few things you need to provide information on:
    • Buffer size
    • Type, source or characteristics of the data (image, text, machine code, binary data files etc)
    • Lossy or lossless compression
    • What balance of speed vs compression ratio
    My homepage
    Advice: Take only as directed - If symptoms persist, please see your debugger

    Linus Torvalds: "But it clearly is the only right way. The fact that everybody else does it some other way only means that they are wrong"

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Replies: 16
    Last Post: 10-29-2006, 04:04 AM
  2. writing a pack-style function, any advices?
    By isaac_s in forum C Programming
    Replies: 10
    Last Post: 07-08-2006, 08:09 PM
  3. buffer contents swapping
    By daluu in forum C++ Programming
    Replies: 7
    Last Post: 10-14-2004, 02:34 PM
  4. Tetris Questions
    By KneeGrow in forum Game Programming
    Replies: 19
    Last Post: 10-28-2003, 10:12 PM
  5. Console Screen Buffer
    By GaPe in forum Windows Programming
    Replies: 0
    Last Post: 02-06-2003, 04:15 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21