switch to refcounted buffers

1 files changed, 87 insertions, 0 deletions

diff --git a/nihav-core/src/refs.rs b/nihav-core/src/refs.rs
new file mode 100644
index 0000000..f2b0577
--- /dev/null
+++ b/nihav-core/src/refs.rs
@@ -0,0 +1,87 @@
+use std::ops::{Deref, DerefMut};
+use std::sync::atomic::*;
+
+struct NABufferData<T> {
+    data:       T,
+    refs:       AtomicUsize,
+}
+
+impl<T> NABufferData<T> {
+    fn new(data: T) -> Self {
+        Self {
+            data:       data,
+            refs:       AtomicUsize::new(1),
+        }
+    }
+    fn inc_refs(obj: &mut Self) {
+        obj.refs.fetch_add(1, Ordering::SeqCst);
+    }
+    fn dec_refs(obj: &mut Self) {
+        if obj.refs.fetch_sub(1, Ordering::SeqCst) == 0 {
+            std::mem::forget(obj);
+        }
+    }
+    fn get_num_refs(obj: &Self) -> usize {
+        obj.refs.load(Ordering::Relaxed)
+    }
+    fn get_read_ptr(obj: &Self) -> &T {
+        &obj.data
+    }
+    fn get_write_ptr(obj: &mut Self) -> Option<&mut T> {
+        Some(&mut obj.data)
+    }
+}
+
+pub struct NABufferRef<T> {
+    ptr: *mut NABufferData<T>,
+}
+
+impl<T> NABufferRef<T> {
+    pub fn new(val: T) -> Self {
+        let bdata = NABufferData::new(val);
+        let nbox: Box<_> = Box::new(bdata);
+        Self { ptr: Box::into_raw(nbox) }
+    }
+    pub fn get_num_refs(&self) -> usize {
+        unsafe {
+            NABufferData::get_num_refs(self.ptr.as_mut().unwrap())
+        }
+    }
+    pub fn as_ref(&self) -> &T {
+        unsafe {
+            NABufferData::get_read_ptr(self.ptr.as_mut().unwrap())
+        }
+    }
+    pub fn as_mut(&mut self) -> Option<&mut T> {
+        unsafe {
+            NABufferData::get_write_ptr(self.ptr.as_mut().unwrap())
+        }
+    }
+}
+
+impl<T> Deref for NABufferRef<T> {
+    type Target = T;
+    fn deref(&self) -> &T { self.as_ref() }
+}
+
+impl<T> DerefMut for NABufferRef<T> {
+    fn deref_mut(&mut self) -> &mut T { self.as_mut().unwrap() }
+}
+
+impl<T> Clone for NABufferRef<T> {
+    fn clone(&self) -> Self {
+        unsafe {
+            NABufferData::inc_refs(self.ptr.as_mut().unwrap());
+        }
+        Self { ptr: self.ptr }
+    }
+}
+
+impl<T> Drop for NABufferRef<T> {
+    fn drop(&mut self) {
+        unsafe {
+            NABufferData::dec_refs(self.ptr.as_mut().unwrap());
+        }
+    }
+}
+