Add DSC decompress support

src/ext/mod.rs

@@ -1 +1,2 @@
 pub mod io;
+pub mod vec;

src/ext/vec.rs

@@ -0,0 +1,22 @@
+pub trait VecExt<T> {
+    /// Copy potentially overlapping sequence of elements from `src` to `dst`.
+    fn copy_overlapped(&mut self, src: usize, dst: usize, len: usize);
+}
+
+impl<T: Copy> VecExt<T> for Vec<T> {
+    fn copy_overlapped(&mut self, src: usize, dst: usize, len: usize) {
+        let src = src.min(self.len());
+        let dst = dst.min(self.len());
+        if src < dst {
+            let max_count = len.min(dst - src);
+            for i in 0..max_count {
+                self[dst + i] = self[src + i];
+            }
+        } else {
+            let max_count = len.min(src - dst);
+            for i in (0..max_count).rev() {
+                self[dst + i] = self[src + i];
+            }
+        }
+    }
+}