Compile on wasm32-wasi

Cargo.toml

@@ -29,6 +29,9 @@ winapi = { version = "0.3.8", features = ["sysinfoapi", "minwindef"] }
 [target.'cfg(target_os = "redox")'.dependencies]
 redox_syscall = "0.1.29"
 
+[target.'cfg(target_os = "wasi")'.dependencies]
+wasi = "0.10"
+
 [features]
 default = [ "format", "parse" ]
 format = [ "num-traits", "pad", "locale" ]

src/system.rs

@@ -69,7 +69,7 @@ fn file_time_as_u64(ft: &FILETIME) -> u64 {
 
 /// Returns the system’s current time, as a tuple of seconds elapsed since
 /// the Unix epoch, and the millisecond of the second.
-#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "redox", windows)))]
+#[cfg(not(any(target_os = "macos", target_os = "ios", target_os = "redox", target_os = "wasi", windows)))]
 pub unsafe fn sys_time() -> (i64, i16) {
     let mut tv = libc::timespec { tv_sec: 0, tv_nsec: 0 };
     let _ = clock_gettime(libc::CLOCK_REALTIME, &mut tv);
@@ -86,6 +86,17 @@ pub fn sys_time() -> (i64, i16) {
    (ts.tv_sec, (ts.tv_nsec / 1000) as i16)
 }
 
+/// Returns the system’s current time, as a tuple of seconds elapsed since
+/// the Unix epoch, and the millisecond of the second.
+///
+/// This may panic if the clock was not made available
+#[cfg(target_os = "wasi")]
+pub unsafe fn sys_time() -> (i64, i16) {
+    let ns = wasi::clock_time_get(wasi::CLOCKID_REALTIME, 1_000_000)
+        .expect("WASI clock unavailable");
+    ((ns / 1_000_000_000) as i64, (ns / 1_000_000 % 1000) as i16)
+}
+
 /// Attempts to determine the system’s current time zone. There’s no
 /// guaranteed way to do this, so this function returns `None` if no
 /// timezone could be found.