From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 compiler/rustc_data_structures/src/unhash.rs | 29 ++++++++++++++++++++++++++++
 1 file changed, 29 insertions(+)
 create mode 100644 compiler/rustc_data_structures/src/unhash.rs

(limited to 'compiler/rustc_data_structures/src/unhash.rs')

diff --git a/compiler/rustc_data_structures/src/unhash.rs b/compiler/rustc_data_structures/src/unhash.rs
new file mode 100644
index 000000000..48e21a9da
--- /dev/null
+++ b/compiler/rustc_data_structures/src/unhash.rs
@@ -0,0 +1,29 @@
+use std::collections::{HashMap, HashSet};
+use std::hash::{BuildHasherDefault, Hasher};
+
+pub type UnhashMap<K, V> = HashMap<K, V, BuildHasherDefault<Unhasher>>;
+pub type UnhashSet<V> = HashSet<V, BuildHasherDefault<Unhasher>>;
+
+/// This no-op hasher expects only a single `write_u64` call. It's intended for
+/// map keys that already have hash-like quality, like `Fingerprint`.
+#[derive(Default)]
+pub struct Unhasher {
+    value: u64,
+}
+
+impl Hasher for Unhasher {
+    #[inline]
+    fn finish(&self) -> u64 {
+        self.value
+    }
+
+    fn write(&mut self, _bytes: &[u8]) {
+        unimplemented!("use write_u64");
+    }
+
+    #[inline]
+    fn write_u64(&mut self, value: u64) {
+        debug_assert_eq!(0, self.value, "Unhasher doesn't mix values!");
+        self.value = value;
+    }
+}
-- 
cgit v1.2.3