charscanner.java

编译器中的词法分析

package cmm.cmmcc;

import cmm.collections.CharBuffer;
import cmm.collections.ICharBuffer;

/**
 * 字符扫描器类，继承共享字符状态类，实现字符流接口
 * @author Huang Xuanxing
 *
 */
public class CharScanner extends SharedCharState implements ICharBuffer {
	public CharBuffer input; // 输入字符流
	
	public CharScanner(String inStr) {
		inStr += "ん"; // 结束符
		initial(inStr);
	}
	
	private void initial(String inStr) {
		input = new CharBuffer(inStr);
		column = 1;
	    line = 1;
	    tokenColumn = 1;
	    tokenLine = 1;
	}
	
	public char LA(int i) {
		return input.LA(i);
	}
	
	public char nextChar() {
		char ch = input.nextChar();
		while (ch == ' ' || ch == '\r' || ch == '\n' || ch == '\t'){
			
			if (ch == '\n') {//遇到回车,行数加1,列数归1
				newline();
				ch = input.nextChar();
			} 
			else if(ch ==' '){//过滤空格
				column++;
				ch = input.nextChar();
			}
			else if(ch == '\r'){//过滤回车前的'\r'字符
				ch = input.nextChar();
			}
			else if(ch =='\t'){//过滤制表符号'\t',一个制表符号为8个字符
				column += 8;
				ch = input.nextChar();
			}
		}
		return ch;
	}
}