From 41c06db2b4926f58e648778c509e82e5eeda4f20 Mon Sep 17 00:00:00 2001
From: Pat Hickey <pat@moreproductive.org>
Date: Mon, 4 Jan 2021 16:28:40 -0800
Subject: [PATCH] finish implementing clocks correctly

---
 crates/wasi-c2/src/ctx.rs                 | 11 +++++++++--
 crates/wasi-c2/src/snapshots/preview_1.rs |  3 ++-
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/crates/wasi-c2/src/ctx.rs b/crates/wasi-c2/src/ctx.rs
index 25792c4d5a..716002ce5a 100644
--- a/crates/wasi-c2/src/ctx.rs
+++ b/crates/wasi-c2/src/ctx.rs
@@ -126,12 +126,19 @@ impl WasiCtxBuilder {
 pub struct WasiCtxClocks {
     pub(crate) system: Box<dyn WasiSystemClock>,
     pub(crate) monotonic: Box<dyn WasiMonotonicClock>,
+    pub(crate) creation_time: cap_std::time::Instant,
 }
 
 impl Default for WasiCtxClocks {
     fn default() -> WasiCtxClocks {
         let system = Box::new(unsafe { cap_std::time::SystemClock::new() });
-        let monotonic = Box::new(unsafe { cap_std::time::MonotonicClock::new() });
-        WasiCtxClocks { system, monotonic }
+        let monotonic = unsafe { cap_std::time::MonotonicClock::new() };
+        let creation_time = monotonic.now();
+        let monotonic = Box::new(monotonic);
+        WasiCtxClocks {
+            system,
+            monotonic,
+            creation_time,
+        }
     }
 }
diff --git a/crates/wasi-c2/src/snapshots/preview_1.rs b/crates/wasi-c2/src/snapshots/preview_1.rs
index a1de4d3de7..f412af21e0 100644
--- a/crates/wasi-c2/src/snapshots/preview_1.rs
+++ b/crates/wasi-c2/src/snapshots/preview_1.rs
@@ -173,7 +173,8 @@ impl<'a> wasi_snapshot_preview1::WasiSnapshotPreview1 for WasiCtx {
             }
             types::Clockid::Monotonic => {
                 let now = self.clocks.monotonic.now(precision);
-                todo!()
+                let d = now.duration_since(self.clocks.creation_time);
+                Ok(d.as_nanos().try_into()?)
             }
             types::Clockid::ProcessCputimeId | types::Clockid::ThreadCputimeId => Err(Error::Badf),
         }