Hide the inner workings of the UnsyncFloatBuf more

src/lib.rs

@@ -312,6 +312,7 @@ pub mod matrix_repr;
 pub mod monitor;
 pub mod nodes;
 pub mod sample_lib;
+pub mod unsync_float_buf;
 mod util;
 
 pub use cell_dir::CellDir;
@@ -323,6 +324,7 @@ pub use matrix_repr::load_patch_from_file;
 pub use matrix_repr::save_patch_to_file;
 pub use nodes::{new_node_engine, NodeConfigurator, NodeExecutor};
 pub use sample_lib::{SampleLibrary, SampleLoadError};
+pub use unsync_float_buf::UnsyncFloatBuf;
 
 pub struct Context<'a, 'b, 'c, 'd> {
     pub nframes: usize,

src/unsync_float_buf.rs

@@ -0,0 +1,129 @@
+// Copyright (c) 2022 Weird Constructor <weirdconstructor@gmail.com>
+// This file is a part of HexoDSP. Released under GPL-3.0-or-later.
+// See README.md and COPYING for details.
+
+use crate::util::AtomicFloat;
+use std::sync::Arc;
+
+/// A float buffer that can be written to and read from in an unsynchronized manner.
+///
+/// One use case is writing samples to this buffer in the audio thread while
+/// a GUI thread reads from this buffer. Mostly useful for an oscilloscope.
+///
+///```
+/// use hexodsp::UnsyncFloatBuf;
+///
+/// let handle1 = UnsyncFloatBuf::new_with_len(10);
+/// let handle2 = handle1.clone();
+///
+/// std::thread::spawn(move || {
+///     handle1.write(9, 2032.0);
+/// }).join().unwrap();
+///
+/// std::thread::spawn(move || {
+///     assert_eq!(handle2.read(9), 2032.0);
+///     assert_eq!(handle2.read(20), 0.0); // out of range!
+/// }).join().unwrap();
+///```
+#[derive(Debug, Clone)]
+pub struct UnsyncFloatBuf(Arc<UnsyncFloatBufImpl>);
+
+impl UnsyncFloatBuf {
+    /// Creates a new unsynchronized float buffer with the given length.
+    pub fn new_with_len(len: usize) -> Self {
+        Self(UnsyncFloatBufImpl::new_shared(len))
+    }
+
+    /// Write float to the given index.
+    ///
+    /// If index is out of range, nothing will be written.
+    pub fn write(&self, idx: usize, v: f32) {
+        self.0.write(idx, v)
+    }
+
+    /// Reads a float from the given index.
+    ///
+    /// If index is out of range, 0.0 will be returned.
+    pub fn read(&self, idx: usize) -> f32 {
+        self.0.read(idx)
+    }
+}
+
+#[derive(Debug)]
+struct UnsyncFloatBufImpl {
+    data_store: Vec<AtomicFloat>,
+    len: usize,
+    ptr: *mut AtomicFloat,
+}
+
+unsafe impl Sync for UnsyncFloatBuf {}
+unsafe impl Send for UnsyncFloatBuf {}
+
+impl UnsyncFloatBufImpl {
+    fn new_shared(len: usize) -> Arc<Self> {
+        let mut rc = Arc::new(Self { data_store: Vec::new(), len, ptr: std::ptr::null_mut() });
+
+        let mut unsync_buf = Arc::get_mut(&mut rc).expect("No other reference to this Arc");
+        unsync_buf.data_store.resize_with(len, || AtomicFloat::new(0.0));
+        // Taking the pointer to the Vec data buffer is fine,
+        // because it will not be moved when inside the Arc.
+        unsync_buf.ptr = unsync_buf.data_store.as_mut_ptr();
+
+        rc
+    }
+
+    fn write(&self, idx: usize, v: f32) {
+        if idx < self.len {
+            unsafe {
+                (*self.ptr.add(idx)).set(v);
+            }
+        }
+    }
+
+    fn read(&self, idx: usize) -> f32 {
+        if idx < self.len {
+            unsafe { (*self.ptr.add(idx)).get() }
+        } else {
+            0.0
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn check_unsync_float_buf_working() {
+        let handle1 = UnsyncFloatBuf::new_with_len(512);
+        for i in 0..512 {
+            handle1.write(i, i as f32);
+        }
+        let handle2 = handle1.clone();
+        for i in 0..512 {
+            assert_eq!(handle2.read(i), i as f32);
+        }
+    }
+
+    #[test]
+    fn check_unsync_float_buf_thread() {
+        let handle1 = UnsyncFloatBuf::new_with_len(512);
+        let handle2 = handle1.clone();
+
+        std::thread::spawn(move || {
+            for i in 0..512 {
+                handle1.write(i, i as f32);
+            }
+        })
+        .join()
+        .unwrap();
+
+        std::thread::spawn(move || {
+            for i in 0..512 {
+                assert_eq!(handle2.read(i), i as f32);
+            }
+        })
+        .join()
+        .unwrap();
+    }
+}