[LintCode] Read Characters From File - Multiple Calls
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.
The read
function may be called multiple times.