LZW实现Java压缩解压

package com.lzg.FileCompress; import java.io.BufferedInputStream; import java.io.BufferedOutputStream; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.util.ArrayList; import java.util.List; public class LzwDecompression { private final int BITS; //֧�� 12 13 14 bits decompression private final int TABLE_SIZE; private final int MAX_VALUE ; private final int MAX_CODE; private BufferedInputStream input = null; private BufferedOutputStream output = null; private int input_bit_count = 0; private int input_bit_buffer = 0; private short[] prefix_code ; private short[] append_character; List<Short> string = new ArrayList<Short>(); List<Short> decode_stack = new ArrayList<Short>(); int decode_stack_count = 0; public LzwDecompression() { this(12); } public LzwDecompression(int bits){ BITS=bits; if(BITS<=12){ TABLE_SIZE=5021; }else if(BITS==13){ TABLE_SIZE=9029; }else TABLE_SIZE=18041; prefix_code = new short[TABLE_SIZE]; append_character = new short[TABLE_SIZE]; MAX_VALUE = (1 << BITS) - 1; MAX_CODE = MAX_VALUE - 1; } public void expand(InputStream is,OutputStream os) throws IOException { input = new BufferedInputStream(is); output = new BufferedOutputStream(os); short next_code; short new_code; short old_code; short character; int counter; next_code = 256; /* This is the next available code to define */ counter = 0; /* Counter is used as a pacifier. */ System.out.println("Expanding..."); old_code = input_code(input); character = old_code; output.write(old_code); while ((new_code = input_code(input)) != MAX_VALUE) { if (++counter == 1000) /* This section of code prints out */ { /* an asterisk every 1000 characters */ counter = 0; /* It is just a pacifier. */ System.out.printf("*"); } string = new ArrayList<Short>(); if (new_code >= next_code) { setListValue(decode_stack, decode_stack_count, character); string.add(character); decode_string(decode_stack_count + 1, old_code); } else { decode_string(decode_stack_count, new_code); } character = string.get(string.size() - 1); for (int i = string.size() - 1; i >= 0; i--) { output.write(string.get(i)); } if (next_code <= MAX_CODE) { prefix_code[next_code] = old_code; append_character[next_code] = character; next_code++; } old_code = new_code; } input.close(); output.close(); } private static void setListValue(List<Short> list, int location, Short value) { if (location >= list.size()) { list.add(value); } else { list.set(location, value); } } private void decode_string(int decode_stack_address, short code) { int i; i = 0; decode_stack_count = decode_stack_address; while (code > 255) { setListValue(decode_stack, decode_stack_count, append_character[code]); decode_stack_count++; string.add(append_character[code]); code = prefix_code[code]; if (i++ >= MAX_CODE) { System.out.println("Fatal error during code expansion."); System.exit(-3); } } setListValue(decode_stack, decode_stack_count, code); string.add(code); } private short input_code(BufferedInputStream bis) throws IOException { int return_value; while (input_bit_count <= 24) { input_bit_buffer |= bis.read() << (24 - input_bit_count); input_bit_count += 8; } return_value = input_bit_buffer >> (32 - BITS); /* C��Java��֮ͬ�� */ if (return_value < 0) return_value += (MAX_VALUE + 1); input_bit_buffer <<= BITS; input_bit_count -= BITS; return (short) return_value; } }