From 5b927b82af73ffec089ac1e09795a90df62055f7 Mon Sep 17 00:00:00 2001
From: Bert Belder <bertbelder@gmail.com>
Date: Tue, 22 Oct 2019 15:46:42 -0700
Subject: [PATCH] wip

---
 src/main.rs             | 46 +-----------------------------
 src/support.rs          |  2 +-
 src/v8/platform/task.rs | 63 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 46 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 62e10490..75a26c8c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,7 +7,6 @@ mod v8;
 mod example {
   use crate::support::UniquePtr;
   use crate::v8::inspector::channel::*;
-  use crate::v8::platform::task::*;
   use crate::v8::*;
 
   pub struct TestChannel {
@@ -47,43 +46,9 @@ mod example {
       }
     }
   }
-
-  pub struct TestTask {
-    a: i32,
-    base: TaskBase,
-    b: i32,
-  }
-
-  impl TaskImpl for TestTask {
-    fn base(&self) -> &TaskBase {
-      &self.base
-    }
-    fn base_mut(&mut self) -> &mut TaskBase {
-      &mut self.base
-    }
-    fn Run(&mut self) -> () {
-      println!("TestTask::Run {} {}", self.a, self.b);
-    }
-  }
-
-  impl TestTask {
-    pub fn new() -> Self {
-      Self {
-        base: TaskBase::new::<Self>(),
-        a: 2,
-        b: 3,
-      }
-    }
-  }
-
-  impl Drop for TestTask {
-    fn drop(&mut self) {
-      println!("TestTask::drop()");
-    }
-  }
 }
 
-fn main1() {
+fn main() {
   use crate::v8::inspector::channel::*;
   use crate::v8::*;
   use example::*;
@@ -94,12 +59,3 @@ fn main1() {
   let message = StringBuffer::create(&message);
   chan.sendResponse(3, message);
 }
-
-fn main() {
-  use crate::v8::platform::task::*;
-  use example::*;
-  let mut v = TestTask::new();
-  v.Run();
-  let b = Box::new(v);
-  b.into_unique_ptr();
-}
diff --git a/src/support.rs b/src/support.rs
index 7d3e661b..9edc0e33 100644
--- a/src/support.rs
+++ b/src/support.rs
@@ -94,7 +94,7 @@ impl<F> FieldOffset<F> {
     let field_addr = field_ptr as usize;
     assert!(field_addr >= embedder_addr);
     assert!((field_addr + size_of::<F>()) <= (embedder_addr + size_of::<E>()));
-    Self(embedder_addr - field_addr, PhantomData)
+    Self(field_addr - embedder_addr, PhantomData)
   }
 
   pub unsafe fn to_embedder<E>(self, field: &F) -> &E {
diff --git a/src/v8/platform/task.rs b/src/v8/platform/task.rs
index 534509ac..b0c01d9a 100644
--- a/src/v8/platform/task.rs
+++ b/src/v8/platform/task.rs
@@ -160,3 +160,66 @@ impl TaskBase {
     std::mem::transmute(Self::dispatch_mut(task))
   }
 }
+
+mod tests {
+  use super::*;
+  use std::sync::atomic::AtomicUsize;
+  use std::sync::atomic::Ordering::SeqCst;
+
+  static RUN_COUNT: AtomicUsize = AtomicUsize::new(0);
+  static DROP_COUNT: AtomicUsize = AtomicUsize::new(0);
+
+  // Using repr(C) to preserve field ordering and test that everything works
+  // when the TaskBase field is not the first element of the struct.
+  #[repr(C)]
+  pub struct TestTask {
+    f1: i32,
+    base: TaskBase,
+    f2: f64,
+  }
+
+  impl TestTask {
+    pub fn new() -> Self {
+      Self {
+        base: TaskBase::new::<Self>(),
+        f1: 42,
+        f2: 4.2,
+      }
+    }
+  }
+
+  impl TaskImpl for TestTask {
+    fn base(&self) -> &TaskBase {
+      &self.base
+    }
+    fn base_mut(&mut self) -> &mut TaskBase {
+      &mut self.base
+    }
+    fn Run(&mut self) -> () {
+      RUN_COUNT.fetch_add(1, SeqCst);
+    }
+  }
+
+  impl Drop for TestTask {
+    fn drop(&mut self) {
+      DROP_COUNT.fetch_add(1, SeqCst);
+    }
+  }
+
+  #[test]
+  fn test_v8_platform_task() {
+    {
+      let mut v = TestTask::new();
+      v.Run();
+    }
+    assert_eq!(RUN_COUNT.swap(0, SeqCst), 1);
+    assert_eq!(DROP_COUNT.swap(0, SeqCst), 1);
+
+    {
+      let b = Box::new(TestTask::new());
+      b.into_unique_ptr();
+    }
+    assert_eq!(RUN_COUNT.swap(0, SeqCst), 0);
+    assert_eq!(DROP_COUNT.swap(0, SeqCst), 1);
+  }
+}