add from_raw_parts and to_raw_parts methods

this is for sending buffers across thread boundaries to
help with argument initializaions

xous-ipc/src/buffer.rs

@@ -1,3 +1,5 @@
+use core::convert::TryInto;
+
 use rkyv::{ser::Serializer, Fallible};
 use xous::{
     map_memory, send_message, unmap_memory, Error, MemoryAddress, MemoryFlags, MemoryMessage,
@@ -72,6 +74,43 @@ impl<'a> Buffer<'a> {
         core::sync::atomic::compiler_fence(core::sync::atomic::Ordering::SeqCst);
     }
 
+    // use to serialize a buffer between process-local threads. mainly for spawning new threads with more complex argument structures.
+    #[allow(dead_code)]
+    pub unsafe fn to_raw_parts(&self) -> (usize, usize, usize) {
+        if let Some(offset) = self.offset {
+            (
+                self.valid.as_ptr() as usize,
+                self.valid.len(),
+                usize::from(offset),
+            )
+        } else {
+            (
+                self.valid.as_ptr() as usize,
+                self.valid.len(),
+                0
+            )
+        }
+    }
+
+    // use to serialize a buffer between process-local threads. mainly for spawning new threads with more complex argument structures.
+    #[allow(dead_code)]
+    pub unsafe fn from_raw_parts(address: usize, len: usize, offset: usize) -> Self {
+        let mem = MemoryRange::new(address, len).expect("invalid memory range args");
+        let off = if offset != 0 {
+            Some(offset.try_into().unwrap())
+        } else {
+            None
+        };
+        Buffer {
+            range: mem,
+            slice: core::slice::from_raw_parts_mut(mem.as_mut_ptr(), mem.len()),
+            valid: mem,
+            offset: off,
+            should_drop: false,
+            memory_message: None,
+        }
+    }
+
     #[allow(dead_code)]
     pub unsafe fn from_memory_message(mem: &'a MemoryMessage) -> Self {
         Buffer {