Remote camera capability.

1 files changed, 44 insertions, 1 deletions

diff --git a/src/v4l2.rs b/src/v4l2.rs
index 0f22aba..a8aff0c 100644
--- a/src/v4l2.rs
+++ b/src/v4l2.rs
@@ -9,11 +9,13 @@ use std::io::Error as IoError;
 use std::fmt::{Display, Debug, Formatter, Error as FmtError};
 use std::error::Error as ErrorTrait;
 use std::{str, iter, array};
+use std::time::Duration;
+use chrono::{DateTime, Local};
 
 macro_rules! define_flagset{
     ($tname:ident: $ctype:ty; $($name:ident = $mask:expr),+) => {
         #[derive(Copy, Clone, Debug, PartialEq, Eq)]
-        pub struct $tname{ $($name: bool),+ }
+        pub struct $tname{ $(pub $name: bool),+ }
         impl $tname{
             pub fn zero() -> Self{
                 Self{ $($name: false),+ }
@@ -166,6 +168,47 @@ pub struct BufAttrs{
     pub timestamp: c::timeval,
     pub sequence: u32,
 }
+impl BufAttrs{
+    // XXX: It is correct only when V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC
+    pub fn get_datetime(&self) -> Option<DateTime<Local>>{
+        let now_monotonic = unsafe{
+            let mut buf = MaybeUninit::uninit();
+            assert!(c::clock_gettime(c::CLOCK_MONOTONIC, buf.as_mut_ptr())
+                == 0);
+            buf.assume_init()
+        };
+        let now_wallclock = Local::now();
+        let mut timestamp = c::timespec{
+            tv_sec: self.timestamp.tv_sec as _,
+            tv_nsec: self.timestamp.tv_usec as _,
+        };
+        timestamp.tv_nsec *= 1000;
+        let (mut so, mut nso, future);
+        if now_monotonic.tv_sec < timestamp.tv_sec
+            || now_monotonic.tv_sec == timestamp.tv_sec
+            && now_monotonic.tv_nsec < timestamp.tv_nsec
+        {
+            future = true;
+            so = timestamp.tv_sec - now_monotonic.tv_sec;
+            nso = timestamp.tv_nsec - now_monotonic.tv_nsec;
+        }else{
+            future = false;
+            so = now_monotonic.tv_sec - timestamp.tv_sec;
+            nso = now_monotonic.tv_nsec - timestamp.tv_nsec;
+        }
+        if nso < 0{
+            nso += 1000_000_000;
+            so -= 1;
+        }
+        assert!(0 <= nso && nso < 1000_000_000);
+        let to = Duration::new(so as u64, nso as u32);
+        if future{
+            Some(now_wallclock + to)
+        }else{
+            Some(now_wallclock - to)
+        }
+    }
+}
 impl Debug for BufAttrs{
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError>{
         #[derive(Debug)]