问如何用C语言打印UTF-8字符串

EN

void read_request(int fd) {
        int size = 50, pos = 0, b;
        char* buffer = calloc(size, 1);

        while (strncmp(buffer + (pos - 4 < 0 ? 0 : pos - 4), "\r\n\r\n", 4)) {
                if ((b = read(fd, buffer + pos, size - pos)) == -1) {
                        perror("read() error");
                        exit(-1);
                }

                pos += b;

                if (pos >= size) {
                        size *= 2;
                        buffer = realloc(buffer, size);
                }
        }

        fwrite(buffer, 1, pos, stdout);
        free(buffer);
}

GET /%D1%82%D0%B5%D1%81%D1%82 HTTP/1.1
Host: 127.0.0.1
User-Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:89.0) Gecko/20100101 Firefox/89.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
DNT: 1
Connection: keep-alive
Upgrade-Insecure-Requests: 1