Add pointer equality comparison for EcoString

Fixes #35

Cargo.toml

@@ -18,4 +18,4 @@ std = []
 serde = { version = "1.0", optional = true, default-features = false }
 
 [target.'cfg(loom)'.dependencies]
-loom = { version = "0.5", optional = true }
+loom = { version = "0.7", optional = true }

src/dynamic.rs

@@ -221,6 +221,23 @@ impl DynamicVec {
     }
 }
 
+impl Eq for DynamicVec {}
+
+impl PartialEq for DynamicVec {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        if let (Variant::Spilled(a), Variant::Spilled(b)) =
+            (self.variant(), other.variant())
+        {
+            if EcoVec::ptr_eq(a, b) {
+                return true;
+            }
+        }
+
+        self.as_slice() == other.as_slice()
+    }
+}
+
 impl Clone for DynamicVec {
     #[inline]
     fn clone(&self) -> Self {

src/string.rs

@@ -57,7 +57,7 @@ macro_rules! eco_format {
 /// The above holds true for normal 32-bit or 64-bit little endian systems. On
 /// 64-bit big-endian systems, the type's size increases to 24 bytes and the
 /// amount of inline storage to 23 bytes.
-#[derive(Clone)]
+#[derive(Clone, Eq, PartialEq)]
 pub struct EcoString(DynamicVec);
 
 impl EcoString {
@@ -281,15 +281,6 @@ impl Display for EcoString {
     }
 }
 
-impl Eq for EcoString {}
-
-impl PartialEq for EcoString {
-    #[inline]
-    fn eq(&self, other: &Self) -> bool {
-        self.as_str().eq(other.as_str())
-    }
-}
-
 impl PartialEq<str> for EcoString {
     #[inline]
     fn eq(&self, other: &str) -> bool {

src/vec.rs

@@ -200,6 +200,13 @@ impl<T> EcoVec<T> {
             ptr::drop_in_place(ptr::slice_from_raw_parts_mut(self.data_mut(), prev));
         }
     }
+
+    /// Whether the two vectors point to the same underlying allocation.
+    ///
+    /// Also returns `true` if both are empty and unallocated.
+    pub fn ptr_eq(a: &Self, b: &Self) -> bool {
+        std::ptr::eq(a.ptr.as_ptr(), b.ptr.as_ptr())
+    }
 }
 
 impl<T: Clone> EcoVec<T> {

tests/tests.rs

@@ -316,6 +316,7 @@ fn test_str_push() {
     v.push('a');
     v.push('b');
     v.push_str("cd😀");
+    assert_eq!(v, v);
     assert_eq!(v, "abcd😀");
     assert_eq!(v.len(), 8);