Read N Characters Given Read4 II - Call multiple times

The API: int read4(char *buf) reads 4 characters at a time from a file.

The return value is the actual number of characters read. For example, it returns 3 if there is only 3 characters left in the file.

By using the read4 API, implement the function int read(char *buf, int n) that reads n characters from the file.

Note:
The read function may be called multiple times.

 

 1 /* The read4 API is defined in the parent class Reader4.

 2       int read4(char[] buf); */

 3 

 4 public class Solution extends Reader4 {

 5     /**

 6      * @param buf Destination buffer

 7      * @param n   Maximum number of characters to read

 8      * @return    The number of characters read

 9      */

10     private char[] tmp = new char[4];

11     private int tmpPoint; //indicate which position we should start reading

12     private int tmpContain;//indicate how many char in the tmp buff

13     public int read(char[] buf, int n) {

14         int cur = 0;

15         while(cur < n){

16             if(tmpPoint == 0){

17                 tmpContain = read4(tmp);

18             }

19             if(tmpContain == 0){

20                 return cur;

21             }

22             while(cur < n && tmpPoint < tmpContain){

23                 buf[cur ++] = tmp[tmpPoint ++];

24             }

25             tmpPoint = tmpPoint % tmpContain;

26         }

27         return cur;

28     }

29 }