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.

// 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) {
        char *curbuf=buf;
        int realn=0;
        while(realn<n)
        {
            int curn=read4(curbuf);
            if(curn<4)
            {
                return min(n,realn+curn);
            }
            else if(curn+realn>=n)return n;
            else
            {
                curbuf+=4;
                realn+=4;
            }
        }

        return realn;
    }
};