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.
Example 1:
Given buf = "abc"
read("abc", 1) // returns "a"
read("abc", 2); // returns "bc"
read("abc", 1); // returns ""
Example 2:
Given buf = "abc"
read("abc", 4) // returns "abc"
read("abc", 1); // returns ""
[leetcode]158. Read N Characters Given Read4 II - Call multiple times 用Read4读取N个字符2 - 调用多次
原文：https://www.cnblogs.com/liuliu5151/p/9808266.html