From 483eb2f56657e8e7f419ab1a4fab8dce9ade8609 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Sat, 27 Apr 2024 20:24:20 +0200
Subject: Adding upstream version 14.2.21.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 src/rocksdb/util/hash_map.h | 67 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 67 insertions(+)
 create mode 100644 src/rocksdb/util/hash_map.h

(limited to 'src/rocksdb/util/hash_map.h')

diff --git a/src/rocksdb/util/hash_map.h b/src/rocksdb/util/hash_map.h
new file mode 100644
index 00000000..7b08fb39
--- /dev/null
+++ b/src/rocksdb/util/hash_map.h
@@ -0,0 +1,67 @@
+//  Copyright (c) 2011-present, Facebook, Inc.  All rights reserved.
+//  This source code is licensed under both the GPLv2 (found in the
+//  COPYING file in the root directory) and Apache 2.0 License
+//  (found in the LICENSE.Apache file in the root directory).
+//
+
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <utility>
+
+#include "util/autovector.h"
+
+namespace rocksdb {
+
+// This is similar to std::unordered_map, except that it tries to avoid
+// allocating or deallocating memory as much as possible. With
+// std::unordered_map, an allocation/deallocation is made for every insertion
+// or deletion because of the requirement that iterators remain valid even
+// with insertions or deletions. This means that the hash chains will be
+// implemented as linked lists.
+//
+// This implementation uses autovector as hash chains insteads.
+//
+template <typename K, typename V, size_t size = 128>
+class HashMap {
+  std::array<autovector<std::pair<K, V>, 1>, size> table_;
+
+ public:
+  bool Contains(K key) {
+    auto& bucket = table_[key % size];
+    auto it = std::find_if(
+        bucket.begin(), bucket.end(),
+        [key](const std::pair<K, V>& p) { return p.first == key; });
+    return it != bucket.end();
+  }
+
+  void Insert(K key, V value) {
+    auto& bucket = table_[key % size];
+    bucket.push_back({key, value});
+  }
+
+  void Delete(K key) {
+    auto& bucket = table_[key % size];
+    auto it = std::find_if(
+        bucket.begin(), bucket.end(),
+        [key](const std::pair<K, V>& p) { return p.first == key; });
+    if (it != bucket.end()) {
+      auto last = bucket.end() - 1;
+      if (it != last) {
+        *it = *last;
+      }
+      bucket.pop_back();
+    }
+  }
+
+  V& Get(K key) {
+    auto& bucket = table_[key % size];
+    auto it = std::find_if(
+        bucket.begin(), bucket.end(),
+        [key](const std::pair<K, V>& p) { return p.first == key; });
+    return it->second;
+  }
+};
+
+}  // namespace rocksdb
-- 
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