LeetCode – Refresh – Read N Characters Given Read4

Read the buffer from file every time. After loop terminated, check whether the total lens is over 4.

Then use n - len (a negative number) to set the end char.

 

// Forward declaration of the read4 API.
int read4(char *buf);

class Solution {
public:
    /**
     * @param buf Destination buffer
     * @param n   Maximum number of characters to read
     * @return    The number of characters read
     */
    int read(char *buf, int n) {
        int len = 0, each = INT_MAX;
        while (len < n && (each = read4(buf))) {
            len += each;
            buf += each;
        }
        if (len >= n) {
            buf[n-len] = '\0';
            len = n;
        }
        return len;
    }
};