Read N Characters Given Read4

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 will only be called once for each test case.

Solution:

/* The read4 API is defined in the parent class Reader4.
      int read4(char[] buf); */
public class Solution extends Reader4 {
  /**
   * @param buf Destination buffer
   * @param n   Maximum number of characters to read
   * @return    The number of characters read
   */
  public int read(char[] buf, int n) {
    boolean eof = false;      // end of file flag
    int total = 0;            // total bytes have read
    char[] tmp = new char[4]; // temp buffer
    while (!eof && total < n) {
      int count = read4(tmp);
      // check if it's the end of the file
      eof = count < 4;
      // get the actual count
      count = Math.min(count, n - total);
      // copy from temp buffer to buf
      for (int i = 0; i < count; i++) 
        buf[total++] = tmp[i];
    }
    return total;
  }
}