From df7bd80d06587d173179df6e0e7c0bbe8bfcb726 Mon Sep 17 00:00:00 2001
From: Nadja Reitzenstein <me@dequbed.space>
Date: Tue, 21 Jun 2022 13:06:12 +0200
Subject: [PATCH] Start on the runtime console subscriber

---
 Cargo.toml                       |  2 +-
 runtime/console/Cargo.toml       | 10 +++++
 runtime/console/src/callsites.rs | 75 ++++++++++++++++++++++++++++++++
 runtime/console/src/lib.rs       | 10 +++++
 4 files changed, 96 insertions(+), 1 deletion(-)
 create mode 100644 runtime/console/Cargo.toml
 create mode 100644 runtime/console/src/callsites.rs
 create mode 100644 runtime/console/src/lib.rs

diff --git a/Cargo.toml b/Cargo.toml
index a50d54c..21b74fd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -123,4 +123,4 @@ tempfile = "3.2"
 shadow-rs = "0.11"
 
 [workspace]
-members = ["modules/*", "api"]
+members = ["runtime/*", "modules/*", "api"]
diff --git a/runtime/console/Cargo.toml b/runtime/console/Cargo.toml
new file mode 100644
index 0000000..45d09e9
--- /dev/null
+++ b/runtime/console/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "console"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+console-api = "0.3"
+tracing = "0.1"
\ No newline at end of file
diff --git a/runtime/console/src/callsites.rs b/runtime/console/src/callsites.rs
new file mode 100644
index 0000000..d10c395
--- /dev/null
+++ b/runtime/console/src/callsites.rs
@@ -0,0 +1,75 @@
+use std::fmt;
+use std::fmt::Formatter;
+use std::ptr;
+use std::sync::atomic::{AtomicPtr, AtomicUsize, Ordering};
+use tracing::Metadata;
+
+pub(crate) struct Callsites<const MAX_CALLSITES: usize> {
+    array: [AtomicPtr<Metadata<'static>>; MAX_CALLSITES],
+    len: AtomicUsize,
+}
+
+impl<const MAX_CALLSITES: usize> Callsites<MAX_CALLSITES> {
+    pub(crate) fn insert(&self, callsite: &'static Metadata<'static>) {
+        if self.contains(callsite) {
+            return;
+        }
+
+        let idx = self.len.fetch_add(1, Ordering::AcqRel);
+        if idx <= MAX_CALLSITES {
+            self.array[idx]
+                .compare_exchange(
+                    ptr::null_mut(),
+                    callsite as *const _ as *mut _,
+                    Ordering::AcqRel,
+                    Ordering::Acquire,
+                )
+                .expect("would have clobbered callsite array");
+        } else {
+            todo!("Need to spill callsite over into backup storage");
+        }
+    }
+
+    pub(crate) fn contains(&self, callsite: &'static Metadata<'static>) -> bool {
+        let mut idx = 0;
+        let mut end = self.len.load(Ordering::Acquire);
+        while {
+            for cs in &self.array[idx..end] {
+                let ptr = cs.load(Ordering::Acquire);
+                let meta = unsafe { ptr as *const _ as &'static Metadata<'static> };
+                if meta.callsite() == callsite.callsite() {
+                    return true;
+                }
+            }
+
+            idx = end;
+
+            // Check if new callsites were added since we iterated
+            end = self.len.load(Ordering::Acquire);
+            end > idx
+        } {}
+
+        false
+    }
+}
+
+impl<const MAX_CALLSITES: usize> Default for Callsites<MAX_CALLSITES> {
+    fn default() -> Self {
+        const NULLPTR: AtomicPtr<_> = AtomicPtr::new(ptr::null_mut());
+        Self {
+            array: [NULLPTR; MAX_CALLSITES],
+            len: AtomicUsize::new(0),
+        }
+    }
+}
+
+impl<const MAX_CALLSITES: usize> fmt::Debug for Callsites<MAX_CALLSITES> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        let len = self.len.load(Ordering::Acquire);
+        f.debug_struct("Callsites")
+            .field("MAX_CALLSITES", &MAX_CALLSITES)
+            .field("array", &&self.array[..len])
+            .field("len", &len)
+            .finish()
+    }
+}
diff --git a/runtime/console/src/lib.rs b/runtime/console/src/lib.rs
new file mode 100644
index 0000000..b02b962
--- /dev/null
+++ b/runtime/console/src/lib.rs
@@ -0,0 +1,10 @@
+mod callsites;
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn it_works() {
+        let result = 2 + 2;
+        assert_eq!(result, 4);
+    }
+}