content: package com.lvrenyang.qrcode;
  
  /**
   * Polynomial
   * 
   * @author Kazuhiko Arase
   */
  class Polynomial {
  
  	private final int[] num;
  
  	public Polynomial(int[] num) {
  		this(num, 0);
  	}
  
  	public Polynomial(int[] num, int shift) {
  
  		int offset = 0;
  
  		while (offset < num.length && num[offset] == 0) {
  			offset++;
  		}
  
  		this.num = new int[num.length - offset + shift];
  		System.arraycopy(num, offset, this.num, 0, num.length - offset);
  	}
  
  	public int get(int index) {
  		return num[index];
  	}
  
  	public int getLength() {
  		return num.length;
  	}
  
  	public String toString() {
  
  		StringBuilder buffer = new StringBuilder();
  
  		for (int i = 0; i < getLength(); i++) {
  			if (i > 0) {
  				buffer.append(",");
  			}
  			buffer.append(get(i));
  		}
  
  		return buffer.toString();
  	}
  
  	public String toLogString() {
  
  		StringBuilder buffer = new StringBuilder();
  
  		for (int i = 0; i < getLength(); i++) {
  			if (i > 0) {
  				buffer.append(",");
  			}
  			buffer.append(QRMath.glog(get(i)));
  
  		}
  
  		return buffer.toString();
  	}
  
  	public Polynomial multiply(Polynomial e) {
  
  		int[] num = new int[getLength() + e.getLength() - 1];
  
  		for (int i = 0; i < getLength(); i++) {
  			for (int j = 0; j < e.getLength(); j++) {
  				num[i + j] ^= QRMath.gexp(QRMath.glog(get(i))
  						+ QRMath.glog(e.get(j)));
  			}
  		}
  
  		return new Polynomial(num);
  	}
  
  	public Polynomial mod(Polynomial e) {
  
  		if (getLength() - e.getLength() < 0) {
  			return this;
  		}
  
  		// 最上位桁の比率
  		int ratio = QRMath.glog(get(0)) - QRMath.glog(e.get(0));
  
  		// コピー作成
  		int[] num = new int[getLength()];
  		for (int i = 0; i < getLength(); i++) {
  			num[i] = get(i);
  		}
  
  		// 引き算して余りを計算
  		for (int i = 0; i < e.getLength(); i++) {
  			num[i] ^= QRMath.gexp(QRMath.glog(e.get(i)) + ratio);
  		}
  
  		// 再帰計算
  		return new Polynomial(num).mod(e);
  	}
  }
  