package?com.lzg.FileCompress;
import?java.io.BufferedInputStream;
import?java.io.BufferedOutputStream;
import?java.io.IOException;
import?java.io.InputStream;
import?java.io.OutputStream;

public?class?LzwCompression?{

	private?final?int?BITS;
	private?final?int?TABLE_SIZE;
	private?final?int?HASHING_SHIFT?=?4;
	private?final?int?MAX_VALUE?;
	private?final?int?MAX_CODE?;

	private?final?int?EOF?=?-1;

	private?BufferedInputStream?input?=?null;
	private?BufferedOutputStream?output?=?null;

	private?int?output_bit_count?=?0;
	private?int?output_bit_buffer?=?0;

	private?short[]?code_value;
	private?short[]?prefix_code;
	private?short[]?append_character;

	public?LzwCompression（）?{
		this（12）;
	}

	public?LzwCompression（int?bits）?{
		BITS?=?bits;
		if?（BITS?<=?12）?{
			TABLE_SIZE?=?5021;
		}?else?if?（BITS?==?13）?{
			TABLE_SIZE?=?9029;
		}?else
			TABLE_SIZE?=?18041;
		code_value?=?new?short[TABLE_SIZE];
		prefix_code?=?new?short[TABLE_SIZE];
		append_character?=?new?short[TABLE_SIZE];
		
		MAX_VALUE?=?（1?<		MAX_CODE?=?MAX_VALUE?-?1;
	}

	public?void?compress（InputStream?is?OutputStream?os）?throws?IOException?{
		input?=?new?BufferedInputStream（is）;
		output?=?new?BufferedOutputStream（os）;
		short?next_code?=?0;
		short?character?=?0;
		short?string_code?=?0;
		short?index?=?0;

		next_code?=?256;

		for?（short?i?=?0;?i?			code_value[i]?=?-1;

		string_code?=?（short）?input.read（）;

		while?（（character?=?（short）?input.read（））?!=?EOF）?{
			index?=?find_match（string_code?character）;

			if?（code_value[index]?!=?-1）?{
				string_code?=?code_value[index];
			}?else?{
				if?（next_code?<=?MAX_CODE）?{
					code_value[index]?=?next_code++;
					prefix_code[index]?=?string_code;
					append_character[index]?=?character;
				}

				output_code（string_code）;
				string_code?=?character;
			}
		}

		output_code（string_code）;
		output_code（（short）?MAX_VALUE）;
		output_code（（short）?0）;

		output.close（）;
		input.close（）;

	}

	private?short?find_match（short?hash_prefix?short?hash_character）?{
		int?index?=?0;
		int?offset?=?0;

		index?=?（hash_character?<
		if?（index?==?0）
			offset?=?1;
		else
			offset?=?TABLE_SIZE?-?index;

		while?（true）?{
			if?（code_value[index]?==?-1）
				return?（short）?index;
			if?（prefix_code[index]?==?hash_prefix
					&&?append_character[index]?==?hash_character）
				return?（short）?index;
			index?-=?offset;
			if?（index?				index?+=?TABLE_SIZE;
		}
	}

	private?void?output_code（short?code）?throws?IOException{
		output_bit_buffer?|=?code?<		output_bit_count?+=?BITS;
		while?（output_bit_count?>=?8）?{
			output.write（output_bit_buffer?>>?24）;
			output_bit_buffer?<<=?8;
			output_bit_count?-=?8;
		}
	}
}

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件???????2889??2011-11-27?16:10??Lzw實現壓縮算法\LzwCompression.java

?????文件???????3791??2011-11-27?14:33??Lzw實現壓縮算法\LzwDecompression.java

?????文件????????608??2011-11-27?14:42??Lzw實現壓縮算法\TestLzw.java

?????目錄??????????0??2011-11-30?09:38??Lzw實現壓縮算法

-----------?---------??----------?-----??----

?????????????????7288????????????????????4