src/main/java/org/wltea/analyzer/core/AnalyzeContext.java
int fillBuffer(Reader reader) throws IOException{
    	int readCount = 0;
    	if(this.buffOffset == 0){
    		//首次读取reader
    		readCount = reader.read(segmentBuff);
    	}else{
    		int offset = this.available - this.cursor;
    		if(offset > 0){
    			//最近一次读取的>最近一次处理的，将未处理的字串拷贝到segmentBuff头部
    			System.arraycopy(this.segmentBuff , this.cursor , this.segmentBuff , 0 , offset);
    			readCount = offset;
    		}
    		//继续读取reader ，以onceReadIn - onceAnalyzed为起始位置，继续填充segmentBuff剩余的部分
    		readCount += reader.read(this.segmentBuff , offset , BUFF_SIZE - offset);
    	}            	
    	//记录最后一次从Reader中读入的可用字符长度
    	this.available = readCount;
    	//重置当前指针
    	this.cursor = 0;
    	return readCount;
    }
int fillBuffer(Reader reader) throws IOException{
    	int readCount = 0;
    	if(this.buffOffset == 0){
    		//首次读取reader
    		readCount = reader.read(segmentBuff);
    	}else{
    		int offset = this.available - this.cursor;
    		if(offset > 0){
    			//最近一次读取的>最近一次处理的，将未处理的字串拷贝到segmentBuff头部
    			System.arraycopy(this.segmentBuff , this.cursor , this.segmentBuff , 0 , offset);
    			readCount = offset;
    		}
    		//继续读取reader ，以onceReadIn - onceAnalyzed为起始位置，继续填充segmentBuff剩余的部分
    		readCount += reader.read(this.segmentBuff , offset , BUFF_SIZE - offset);
    	}            	
    	//记录最后一次从Reader中读入的可用字符长度
    	this.available = readCount;
    	//重置当前指针
    	this.cursor = 0;
    	return readCount;
    }
int fillBuffer ( Reader reader ) throws IOException { int readCount = 0 ; if ( this . buffOffset == 0 ) { //首次读取reader
 readCount = reader . read ( segmentBuff ) ; } else { int offset = this . available - this . cursor ; if ( offset > 0 ) { //最近一次读取的>最近一次处理的，将未处理的字串拷贝到segmentBuff头部
 System . arraycopy ( this . segmentBuff , this . cursor , this . segmentBuff , 0 , offset ) ; readCount = offset ; } //继续读取reader ，以onceReadIn - onceAnalyzed为起始位置，继续填充segmentBuff剩余的部分
 readCount += reader . read ( this . segmentBuff , offset , BUFF_SIZE - offset ) ; } //记录最后一次从Reader中读入的可用字符长度
 this . available = readCount ; //重置当前指针
 this . cursor = 0 ; return readCount ; }
根据context的上下文情况，填充segmentBuff
@param reader
@return 返回待分析的（有效的）字串长度
@throws java.io.IOException
根据context的上下文情况，填充segmentBuff