1 files changed, 31 insertions, 1 deletions
diff --git a/src/metadata.rs b/src/metadata.rs
index ef49bcb..746b593 100644
--- a/src/metadata.rs
+++ b/src/metadata.rs
@@ -1,7 +1,8 @@
 // Copyright 2019 TiKV Project Authors. Licensed under Apache-2.0.
 
-use crate::grpc_sys::{self, grpc_metadata_array};
+use crate::grpc_sys::{self, grpc_metadata, grpc_metadata_array};
 use std::borrow::Cow;
+use std::mem::ManuallyDrop;
 use std::{mem, slice, str};
 
 use crate::error::{Error, Result};
@@ -184,6 +185,35 @@ impl Metadata {
             index: 0,
         }
     }
+
+    /// Decomposes a Metadata array into its raw components.
+    ///
+    /// Returns the raw pointer to the underlying data, the length of the vector (in elements),
+    /// and the allocated capacity of the data (in elements). These are the same arguments in
+    /// the same order as the arguments to from_raw_parts.
+    ///
+    /// After calling this function, the caller is responsible for the memory previously managed
+    /// by the Metadata. The only way to do this is to convert the raw pointer, length, and
+    /// capacity back into a Metadata with the from_raw_parts function, allowing the destructor
+    /// to perform the cleanup.
+    pub fn into_raw_parts(self) -> (*mut grpc_metadata, usize, usize) {
+        let s = ManuallyDrop::new(self);
+        (s.0.metadata, s.0.count, s.0.capacity)
+    }
+
+    /// Creates a Metadata directly from the raw components of another vector.
+    ///
+    /// ## Safety
+    ///
+    /// The operation is safe only if the three arguments are returned from `into_raw_parts`
+    /// and only convert once.
+    pub unsafe fn from_raw_parts(p: *mut grpc_metadata, len: usize, cap: usize) -> Metadata {
+        Metadata(grpc_metadata_array {
+            count: len,
+            capacity: cap,
+            metadata: p,
+        })
+    }
 }
 
 impl Clone for Metadata {