feat: add reference rust-memalloc

__internal/memory/README.md

@@ -2,3 +2,26 @@
 Reference:
 * https://radu-matei.com/blog/practical-guide-to-wasm-memory/ [practical-guide-to-wasm-memory.pdf](https://playsecurity.org/doc/showDocDetail.jssp?id=6143)
 * https://github.com/alec-deason/wasm_plugin/blob/main/guest/src/lib.rs
+* https://github.com/reem/rust-memalloc/blob/master/src/lib.rs
+
+**rust-memalloc** implements `reallocate`:
+```rust
+pub unsafe fn reallocate(ptr: *mut u8, old_size: usize, new_size: usize) -> *mut u8 {
+    if old_size > new_size {
+        let mut buf = Vec::from_raw_parts(ptr, new_size, old_size);
+        buf.shrink_to_fit();
+
+        ptr_from_vec(buf)
+    } else if new_size > old_size {
+        let additional = new_size - old_size;
+
+        let mut buf = Vec::from_raw_parts(ptr, 0, old_size);
+        buf.reserve_exact(additional);
+
+        ptr_from_vec(buf)
+    } else {
+        ptr
+    }
+}
+```
+