Impl unsafe deref_mut on IpcSharedMemory

Signed-off-by: sagudev <16504129+sagudev@users.noreply.github.com>

src/ipc.rs

@@ -570,6 +570,24 @@ impl Deref for IpcSharedMemory {
     }
 }
 
+impl IpcSharedMemory {
+    /// Returns a mutable reference to the deref of this [`IpcSharedMemory`].
+    ///
+    /// # Safety
+    ///
+    /// This is safe if there is only one reader/writer on the data.
+    /// User can achieve this by not cloning [`IpcSharedMemory`]
+    /// and serializing/deserializing only once.
+    #[inline]
+    pub unsafe fn deref_mut(&mut self) -> &mut [u8] {
+        if let Some(os_shared_memory) = &mut self.os_shared_memory {
+            os_shared_memory.deref_mut()
+        } else {
+            &mut []
+        }
+    }
+}
+
 impl<'de> Deserialize<'de> for IpcSharedMemory {
     fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
     where

src/platform/inprocess/mod.rs

@@ -395,6 +395,16 @@ impl Deref for OsIpcSharedMemory {
     }
 }
 
+impl OsIpcSharedMemory {
+    #[inline]
+    pub unsafe fn deref_mut(&mut self) -> &mut [u8] {
+        if self.ptr.is_null() {
+            panic!("attempted to access a consumed `OsIpcSharedMemory`")
+        }
+        unsafe { slice::from_raw_parts_mut(self.ptr, self.length) }
+    }
+}
+
 impl OsIpcSharedMemory {
     pub fn from_byte(byte: u8, length: usize) -> OsIpcSharedMemory {
         let mut v = Arc::new(vec![byte; length]);

src/platform/macos/mod.rs

@@ -940,6 +940,16 @@ impl Deref for OsIpcSharedMemory {
     }
 }
 
+impl OsIpcSharedMemory {
+    #[inline]
+    pub unsafe fn deref_mut(&mut self) -> &mut [u8] {
+        if self.ptr.is_null() && self.length > 0 {
+            panic!("attempted to access a consumed `OsIpcSharedMemory`")
+        }
+        unsafe { slice::from_raw_parts_mut(self.ptr, self.length) }
+    }
+}
+
 impl OsIpcSharedMemory {
     unsafe fn from_raw_parts(ptr: *mut u8, length: usize) -> OsIpcSharedMemory {
         OsIpcSharedMemory {

src/platform/unix/mod.rs

@@ -31,7 +31,7 @@ use std::hash::BuildHasherDefault;
 use std::io;
 use std::marker::PhantomData;
 use std::mem;
-use std::ops::{Deref, RangeFrom};
+use std::ops::{Deref, DerefMut, RangeFrom};
 use std::os::fd::RawFd;
 use std::ptr;
 use std::slice;
@@ -866,6 +866,13 @@ impl Deref for OsIpcSharedMemory {
     }
 }
 
+impl OsIpcSharedMemory {
+    #[inline]
+    pub unsafe fn deref_mut(&mut self) -> &mut [u8] {
+        unsafe { slice::from_raw_parts_mut(self.ptr, self.length) }
+    }
+}
+
 impl OsIpcSharedMemory {
     unsafe fn from_raw_parts(
         ptr: *mut u8,

src/platform/windows/mod.rs

@@ -1834,6 +1834,14 @@ impl Deref for OsIpcSharedMemory {
     }
 }
 
+impl OsIpcSharedMemory {
+    #[inline]
+    pub unsafe fn deref_mut(&mut self) -> &mut [u8] {
+        assert!(!self.view_handle.Value.is_null() && self.handle.is_valid());
+        unsafe { slice::from_raw_parts_mut(self.view_handle.Value as _, self.length) }
+    }
+}
+
 impl OsIpcSharedMemory {
     fn new(length: usize) -> Result<OsIpcSharedMemory, WinError> {
         unsafe {