Read N Characters Given Read4 II - Call multiple times @LeetCode

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.

	/*
	* The read function may be called multiple times.
	* The previous one we can't use it for multiple times since read4 actually read more and break continuity.
	* This one will sovle that problem. read the buffer used last time.(through offset)
	*/
	public class Read4KII {
	// reused variable.
	private char[] buffer = new char[4];
	private int bufsize = 0;
	private int offset = 0;
	public int read(char[] buf, int n) {
	int total = 0;
	boolean eof = true;
	while (eof && total < n) {
	if (bufsize == 0) {
	bufsize = read4(buffer);
	if (bufsize < 4) {
	eof = false;
	}
	}
	int bytes = Math.min(n - total, bufsize);
	System.arraycopy(buffer, offset, buf, total, bytes);
	offset = (offset + bytes) % 4;
	bufsize -= bytes;
	total += bytes;
	}
	return total;
	}
	// API funciton
	public int read4(char[] buf) {
	return 0;
	}

view raw Read4KII.java hosted with ❤ by GitHub