org.apache.poi.util.LZWDecompresser
org.apache.poi.hdgf.HDGFLZW
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java.lang.Object
public class HDGFLZW
A decoder for the crazy LZW implementation used in Visio. According to VSDump, "it's a slightly perverted version of LZW compression, with inverted meaning of flag byte and 0xFEE as an 'initial shift'". It uses 12 bit codes (http://www.gnome.ru/projects/vsdump_en.html) Two good resources on LZW are: http://en.wikipedia.org/wiki/LZW http://marknelson.us/1989/10/01/lzw-data-compression/
| Constructor Summary | |
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HDGFLZW()
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| Method Summary | |
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protected int |
adjustDictionaryOffset(int pntr)
We have a slight shift by 18 bytes |
byte[] |
compress(java.io.InputStream src)
Compress the given input stream, returning the array of bytes of the compressed input |
void |
compress(java.io.InputStream src,
java.io.OutputStream res)
Performs the Visio compatible streaming LZW compression. |
protected int |
populateDictionary(byte[] dict)
We want an empty dictionary, so do nothing |
| Methods inherited from class org.apache.poi.util.LZWDecompresser |
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decompress, decompress, fromByte, fromInt |
| Methods inherited from class java.lang.Object |
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clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Constructor Detail |
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public HDGFLZW()
| Method Detail |
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public byte[] compress(java.io.InputStream src)
throws java.io.IOException
java.io.IOExceptionprotected int adjustDictionaryOffset(int pntr)
adjustDictionaryOffset in class LZWDecompresserprotected int populateDictionary(byte[] dict)
populateDictionary in class LZWDecompresser
public void compress(java.io.InputStream src,
java.io.OutputStream res)
throws java.io.IOException
java.io.IOException
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