C++ line-buffered output for Android (for usage in JNI)

class.cpp

class androidbuf: public std::streambuf {
public:
    enum { bufsize = 1024 };
    androidbuf() { this->setp(0, 0); }
private:
    int overflow(int c) {
        if (c == traits_type::eof() || c == '\n' || idx == bufsize - 1) {
            buffer[idx] = '\0';
            idx++;
            
            __android_log_print(ANDROID_LOG_INFO, "yourlibrary", "%s", buffer);

            idx = 0;
        }

        if (!(c == traits_type::eof() || c == '\n')) {
       		buffer[idx] = c;
       		idx++;
        }

        return c;
    }
    char buffer[bufsize];
    int idx = 0;
};

usage.cpp

std::cout.rdbuf(new androidbuf);