1 files changed, 78 insertions, 0 deletions
diff --git a/library/alloc/src/raw_vec/tests.rs b/library/alloc/src/raw_vec/tests.rs
new file mode 100644
index 00000000000..5408faa079c
--- /dev/null
+++ b/library/alloc/src/raw_vec/tests.rs
@@ -0,0 +1,78 @@
+use super::*;
+
+#[test]
+fn allocator_param() {
+    use crate::alloc::AllocErr;
+
+    // Writing a test of integration between third-party
+    // allocators and `RawVec` is a little tricky because the `RawVec`
+    // API does not expose fallible allocation methods, so we
+    // cannot check what happens when allocator is exhausted
+    // (beyond detecting a panic).
+    //
+    // Instead, this just checks that the `RawVec` methods do at
+    // least go through the Allocator API when it reserves
+    // storage.
+
+    // A dumb allocator that consumes a fixed amount of fuel
+    // before allocation attempts start failing.
+    struct BoundedAlloc {
+        fuel: usize,
+    }
+    unsafe impl AllocRef for BoundedAlloc {
+        fn alloc(&mut self, layout: Layout, init: AllocInit) -> Result<MemoryBlock, AllocErr> {
+            let size = layout.size();
+            if size > self.fuel {
+                return Err(AllocErr);
+            }
+            match Global.alloc(layout, init) {
+                ok @ Ok(_) => {
+                    self.fuel -= size;
+                    ok
+                }
+                err @ Err(_) => err,
+            }
+        }
+        unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
+            unsafe { Global.dealloc(ptr, layout) }
+        }
+    }
+
+    let a = BoundedAlloc { fuel: 500 };
+    let mut v: RawVec<u8, _> = RawVec::with_capacity_in(50, a);
+    assert_eq!(v.alloc.fuel, 450);
+    v.reserve(50, 150); // (causes a realloc, thus using 50 + 150 = 200 units of fuel)
+    assert_eq!(v.alloc.fuel, 250);
+}
+
+#[test]
+fn reserve_does_not_overallocate() {
+    {
+        let mut v: RawVec<u32> = RawVec::new();
+        // First, `reserve` allocates like `reserve_exact`.
+        v.reserve(0, 9);
+        assert_eq!(9, v.capacity());
+    }
+
+    {
+        let mut v: RawVec<u32> = RawVec::new();
+        v.reserve(0, 7);
+        assert_eq!(7, v.capacity());
+        // 97 is more than double of 7, so `reserve` should work
+        // like `reserve_exact`.
+        v.reserve(7, 90);
+        assert_eq!(97, v.capacity());
+    }
+
+    {
+        let mut v: RawVec<u32> = RawVec::new();
+        v.reserve(0, 12);
+        assert_eq!(12, v.capacity());
+        v.reserve(12, 3);
+        // 3 is less than half of 12, so `reserve` must grow
+        // exponentially. At the time of writing this test grow
+        // factor is 2, so new capacity is 24, however, grow factor
+        // of 1.5 is OK too. Hence `>= 18` in assert.
+        assert!(v.capacity() >= 12 + 12 / 2);
+    }
+}