1 files changed, 333 insertions, 0 deletions
diff --git a/meap/meap-code/ch9/ch9-clock3/src/main.rs b/meap/meap-code/ch9/ch9-clock3/src/main.rs
new file mode 100755
index 0000000..ad3ee9f
--- /dev/null
+++ b/meap/meap-code/ch9/ch9-clock3/src/main.rs
@@ -0,0 +1,333 @@
+extern crate byteorder;
+extern crate chrono;
+extern crate clap;
+#[cfg(not(windows))] extern crate libc;
+#[cfg(windows)] extern crate kernel32;
+#[cfg(windows)] extern crate winapi;
+
+use byteorder::{BigEndian, ReadBytesExt};
+use chrono::DateTime;
+use chrono::Duration as ChronoDuration;
+use chrono::{Datelike, TimeZone, Timelike};
+use chrono::{Local, Utc};
+use clap::{App, Arg};
+use std::mem::zeroed;
+use std::net::UdpSocket;
+use std::time::Duration;
+
+const NTP_MESSAGE_LENGTH: usize = 48; // 12*4 bytes
+const NTP_TO_UNIX_SECONDS: i64 = 2_208_988_800;
+const LOCAL_ADDR: &'static str = "0.0.0.0:12300";
+
+#[derive(Default, Debug, Copy, Clone)]
+struct NTPTimestamp {
+    seconds: u32,
+    fraction: u32,
+}
+
+struct NTPMessage {
+    data: [u8; NTP_MESSAGE_LENGTH],
+}
+
+#[derive(Debug)]
+struct NTPResult {
+    t1: DateTime<Utc>,
+    t2: DateTime<Utc>,
+    t3: DateTime<Utc>,
+    t4: DateTime<Utc>,
+}
+
+impl NTPResult {
+    fn offset(&self) -> i64 {
+        let duration = (self.t2 - self.t1) + (self.t3 - self.t4);
+        duration.num_milliseconds() / 2
+    }
+
+    fn delay(&self) -> i64 {
+        let duration = (self.t4 - self.t1) - (self.t3 - self.t2);
+        duration.num_milliseconds()
+    }
+}
+
+impl From<NTPTimestamp> for DateTime<Utc> {
+    fn from(ntp: NTPTimestamp) -> Self {
+        let secs = ntp.seconds as i64 - NTP_TO_UNIX_SECONDS;
+        let mut nanos = ntp.fraction as f64;
+        nanos *= 1e9;
+        nanos /= 2_f64.powi(32);
+
+        Utc.timestamp(secs, nanos as u32)
+    }
+}
+
+impl From<DateTime<Utc>> for NTPTimestamp {
+    fn from(utc: DateTime<Utc>) -> Self {
+        let secs = utc.timestamp() + NTP_TO_UNIX_SECONDS;
+        let mut fraction = utc.nanosecond() as f64;
+        fraction *= 2_f64.powi(32);
+        fraction /= 1e9;
+
+        NTPTimestamp {
+            seconds: secs as u32,
+            fraction: fraction as u32,
+        }
+    }
+}
+
+impl NTPMessage {
+    fn new() -> Self {
+        NTPMessage {
+            data: [0; NTP_MESSAGE_LENGTH],
+        }
+    }
+
+    fn client() -> Self {
+        const VERSION: u8 = 3;
+        const MODE: u8 = 3;
+
+        let mut msg = NTPMessage::new();
+
+        // the first byte of every NTP message contains three fields,
+        // but we only need to set two of them
+        msg.data[0] |= VERSION << 3;
+        msg.data[0] |= MODE;
+        msg
+    }
+
+    fn parse_timestamp(&self, i: usize) -> Result<NTPTimestamp, std::io::Error> {
+        let mut reader = &self.data[i..i + 8];
+        let seconds = reader.read_u32::<BigEndian>()?;
+        let fraction = reader.read_u32::<BigEndian>()?;
+
+        Ok(NTPTimestamp {
+            seconds: seconds,
+            fraction: fraction,
+        })
+    }
+
+    fn rx_time(&self) -> Result<NTPTimestamp, std::io::Error> {
+        self.parse_timestamp(32)
+    }
+
+    fn tx_time(&self) -> Result<NTPTimestamp, std::io::Error> {
+        self.parse_timestamp(40)
+    }
+}
+
+fn weighted_mean(values: &[f64], weights: &[f64]) -> f64 {
+    let mut result = 0.0;
+    let mut sum_of_weights = 0.0;
+
+    for (v, w) in values.iter().zip(weights) {
+        result += v * w;
+        sum_of_weights += w;
+    }
+
+    result / sum_of_weights
+}
+
+fn ntp_roundtrip(host: &str, port: u16) -> Result<NTPResult, std::io::Error> {
+    let destination = format!("{}:{}", host, port);
+    let timeout = Duration::from_secs(1);
+
+    let request = NTPMessage::client();
+    let mut response = NTPMessage::new();
+
+    let message = request.data;
+
+    let udp = UdpSocket::bind(LOCAL_ADDR)?;
+    udp.connect(&destination).expect("unable to connect");
+
+    let t1 = Utc::now();
+    udp.send(&message)?;
+    udp.set_read_timeout(Some(timeout))?;
+    udp.recv_from(&mut response.data)?;
+    let t4 = Utc::now();
+
+    let t2: DateTime<Utc> = response.rx_time().unwrap().into();
+    let t3: DateTime<Utc> = response.tx_time().unwrap().into();
+
+    Ok(NTPResult {
+        t1: t1,
+        t2: t2,
+        t3: t3,
+        t4: t4,
+    })
+}
+
+fn check_time() -> Result<f64, std::io::Error> {
+    const NTP_PORT: u16 = 123;
+
+    let servers = [
+        "time.nist.gov",
+        "time.apple.com",
+        "time.euro.apple.com",
+        "time.google.com",
+        "time2.google.com",
+        //"time.windows.com",
+    ];
+
+    let mut times = Vec::with_capacity(servers.len());
+
+    for &server in servers.iter() {
+        print!("{} =>", server);
+
+        let calc = ntp_roundtrip(&server, NTP_PORT);
+
+        match calc {
+            Ok(time) => {
+                println!(" {}ms away from local system time", time.offset());
+                times.push(time);
+            }
+            Err(_) => println!(" ? [response took too long]"),
+        };
+    }
+
+    let mut offsets = Vec::with_capacity(servers.len());
+    let mut offset_weights = Vec::with_capacity(servers.len());
+
+    for time in &times {
+        let offset = time.offset() as f64;
+        let delay = time.delay() as f64;
+
+        let weight = 1_000_000.0 / (delay * delay); // <3>
+        if weight.is_finite() {
+            offsets.push(offset);
+            offset_weights.push(weight);
+        }
+    }
+
+    let avg_offset = weighted_mean(&offsets, &offset_weights);
+
+    Ok(avg_offset)
+}
+
+struct Clock;
+
+impl Clock {
+    fn get() -> DateTime<Local> {
+        Local::now()
+    }
+
+    #[cfg(windows)]
+    fn set<Tz: TimeZone>(t: DateTime<Tz>) -> () {
+        use chrono::Weekday;
+        use kernel32::SetSystemTime;
+        use winapi::{SYSTEMTIME, WORD};
+
+        let t = t.with_timezone(&Local);
+
+        let mut systime: SYSTEMTIME = unsafe { zeroed() };
+
+        let dow = match t.weekday() {
+            Weekday::Mon => 1,
+            Weekday::Tue => 2,
+            Weekday::Wed => 3,
+            Weekday::Thu => 4,
+            Weekday::Fri => 5,
+            Weekday::Sat => 6,
+            Weekday::Sun => 0,
+        };
+
+        let mut ns = t.nanosecond();
+        let is_leap_second = ns > 1_000_000_000;
+
+        if is_leap_second {
+            ns -= 1_000_000_000;
+        }
+
+        systime.wYear = t.year() as WORD;
+        systime.wMonth = t.month() as WORD;
+        systime.wDayOfWeek = dow as WORD;
+        systime.wDay = t.day() as WORD;
+        systime.wHour = t.hour() as WORD;
+        systime.wMinute = t.minute() as WORD;
+        systime.wSecond = t.second() as WORD;
+        systime.wMilliseconds = (ns / 1_000_000) as WORD;
+
+        let systime_ptr = &systime as *const SYSTEMTIME; // as *mut SYSTEMTIME; // convert to a pointer, then change its mutability
+
+        unsafe {
+            SetSystemTime(systime_ptr); // giving a pointer to a value to something outside of Rust's control is unsafe
+        }
+    }
+
+    #[cfg(not(windows))]
+    fn set<Tz: TimeZone>(t: DateTime<Tz>) -> () {
+        use libc::settimeofday;
+        use libc::{suseconds_t, time_t, timeval, timezone};
+
+        let t = t.with_timezone(&Local); // variable names indicate the data's progression
+        let mut u: timeval = unsafe { zeroed() }; // through the function
+
+        u.tv_sec = t.timestamp() as time_t;
+        u.tv_usec = t.timestamp_subsec_micros() as suseconds_t;
+
+        unsafe {
+            let mock_tz: *const timezone = std::ptr::null();
+            settimeofday(&u as *const timeval, mock_tz);
+        }
+    }
+}
+
+fn main() {
+    let app = App::new("clock")
+        .version("0.1.3")
+        .about("Gets and sets the time.")
+        .after_help("Note: UNIX timestamps are parsed as whole seconds since 1st January 1970 0:00:00 UTC. For more accuracy, use another format.")
+        .arg(Arg::with_name("action")
+            .takes_value(true)
+            .possible_values(&["get", "set", "check-ntp"])
+            .default_value("get"))
+        .arg(Arg::with_name("std")
+            .short("s")
+            .long("use-standard")
+            .takes_value(true)
+            .possible_values(&["rfc2822", "rfc3339", "timestamp"])
+            .default_value("rfc3339"))
+        .arg(Arg::with_name("datetime")
+            .help("When <action> is 'set', apply <datetime>. Otherwise, ignore."));
+
+    let args = app.get_matches();
+
+    let action = args.value_of("action").unwrap(); // default_value() has been supplied,
+    let std = args.value_of("std").unwrap(); // so it's safe to use .unwrap()
+
+    if action == "set" {
+        let t_ = args.value_of("datetime").unwrap();
+
+        let parser = match std {
+            "rfc2822" => DateTime::parse_from_rfc2822,
+            "rfc3339" => DateTime::parse_from_rfc3339,
+            _ => unimplemented!(),
+        };
+
+        let err_msg = format!("Unable to parse {} according to {}", t_, std);
+        let t = parser(t_).expect(&err_msg);
+
+        Clock::set(t);
+    } else if action == "check-ntp" {
+        let offset = check_time().unwrap() as isize;
+        let adjust_ms = offset.signum() * offset.abs().min(200) / 5;
+        let adjust_ms_ = ChronoDuration::milliseconds(adjust_ms as i64);
+        let now: DateTime<Utc> = Utc::now() + adjust_ms_;
+        Clock::set(now);
+    }
+
+    let maybe_error = std::io::Error::last_os_error();
+    let os_error_code = &maybe_error.raw_os_error();
+    match os_error_code {
+        Some(0) => (),
+        None => (),
+        _ => eprintln!("Unable to set the time: {:?}", maybe_error),
+    }
+
+    let now = Clock::get();
+
+    match std {
+        "timestamp" => println!("{}", now.timestamp()),
+        "rfc2822" => println!("{}", now.to_rfc2822()),
+        "rfc3339" => println!("{}", now.to_rfc3339()),
+        _ => unreachable!(),
+    }
+}