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diff --git a/headers/skiplist.cuh b/headers/skiplist.cuh
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+++ b/headers/skiplist.cuh
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+//
+// Created by user on 05/11/2021.
+//
+
+#ifndef CLEVELDB_SKIPLIST_CUH
+#define CLEVELDB_SKIPLIST_CUH
+
+#include <atomic>
+#include <cassert>
+#include <cstdlib>
+
+#include "arena.h"
+#include "../utils/random.h"
+
+namespace cleveldb {
+
+	class Arena;
+
+	template <typename Key, class Comparator>
+	class SkipList {
+	private:
+		struct Node;
+
+	public:
+		// Create a new SkipList object that will use "cmp" for comparing keys,
+		// and will allocate memory using "*arena".  Objects allocated in the arena
+		// must remain allocated for the lifetime of the skiplist object.
+		explicit SkipList(Comparator cmp, Arena* arena);
+
+		SkipList(const SkipList&) = delete;
+		SkipList& operator=(const SkipList&) = delete;
+
+		// Insert key into the list.
+		// REQUIRES: nothing that compares equal to key is currently in the list.
+		void Insert(const Key& key);
+
+		// Returns true iff an entry that compares equal to key is in the list.
+		bool Contains(const Key& key) const;
+
+		// Iteration over the contents of a skip list
+		class Iterator {
+		public:
+			// Initialize an iterator over the specified list.
+			// The returned iterator is not valid.
+			explicit Iterator(const SkipList* list);
+
+			// Returns true iff the iterator is positioned at a valid node.
+			bool Valid() const;
+
+			// Returns the key at the current position.
+			// REQUIRES: Valid()
+			const Key& key() const;
+
+			// Advances to the next position.
+			// REQUIRES: Valid()
+			void Next();
+
+			// Advances to the previous position.
+			// REQUIRES: Valid()
+			void Prev();
+
+			// Advance to the first entry with a key >= target
+			void Seek(const Key& target);
+
+			// Position at the first entry in list.
+			// Final state of iterator is Valid() iff list is not empty.
+			void SeekToFirst();
+
+			// Position at the last entry in list.
+			// Final state of iterator is Valid() iff list is not empty.
+			void SeekToLast();
+
+		private:
+			const SkipList* list_;
+			Node* node_;
+			// Intentionally copyable
+		};
+
+	private:
+		enum { kMaxHeight = 12 };
+
+		inline int GetMaxHeight() const {
+			return max_height_.load(std::memory_order_relaxed);
+		}
+
+		Node* NewNode(const Key& key, int height);
+		int RandomHeight();
+		bool Equal(const Key& a, const Key& b) const { return (compare_(a, b) == 0); }
+
+		// Return true if key is greater than the data stored in "n"
+		bool KeyIsAfterNode(const Key& key, Node* n) const;
+
+		// Return the earliest node that comes at or after key.
+		// Return nullptr if there is no such node.
+		//
+		// If prev is non-null, fills prev[level] with pointer to previous
+		// node at "level" for every level in [0..max_height_-1].
+		Node* FindGreaterOrEqual(const Key& key, Node** prev) const;
+
+		// Return the latest node with a key < key.
+		// Return head_ if there is no such node.
+		Node* FindLessThan(const Key& key) const;
+
+		// Return the last node in the list.
+		// Return head_ if list is empty.
+		Node* FindLast() const;
+
+		// Immutable after construction
+		Comparator const compare_;
+		Arena* const arena_;  // Arena used for allocations of nodes
+
+		Node* const head_;
+
+		// Modified only by Insert().  Read racily by readers, but stale
+		// values are ok.
+		std::atomic<int> max_height_;  // Height of the entire list
+
+		// Read/written only by Insert().
+		Random rnd_;
+	};
+
+// Implementation details follow
+	template <typename Key, class Comparator>
+	struct SkipList<Key, Comparator>::Node {
+		explicit Node(const Key& k) : key(k) {}
+
+		Key const key;
+
+		// Accessors/mutators for links.  Wrapped in methods so we can
+		// add the appropriate barriers as necessary.
+		Node* Next(int n) {
+			assert(n >= 0);
+			// Use an 'acquire load' so that we observe a fully initialized
+			// version of the returned Node.
+			return next_[n].load(std::memory_order_acquire);
+		}
+		void SetNext(int n, Node* x) {
+			assert(n >= 0);
+			// Use a 'release store' so that anybody who reads through this
+			// pointer observes a fully initialized version of the inserted node.
+			next_[n].store(x, std::memory_order_release);
+		}
+
+		// No-barrier variants that can be safely used in a few locations.
+		Node* NoBarrier_Next(int n) {
+			assert(n >= 0);
+			return next_[n].load(std::memory_order_relaxed);
+		}
+		void NoBarrier_SetNext(int n, Node* x) {
+			assert(n >= 0);
+			next_[n].store(x, std::memory_order_relaxed);
+		}
+
+	private:
+		// Array of length equal to the node height.  next_[0] is lowest level link.
+		std::atomic<Node*> next_[1];
+	};
+
+	template <typename Key, class Comparator>
+	typename SkipList<Key, Comparator>::Node* SkipList<Key, Comparator>::NewNode(
+			const Key& key, int height) {
+		char* const node_memory = arena_->AllocateAligned(
+				sizeof(Node) + sizeof(std::atomic<Node*>) * (height - 1));
+		return new (node_memory) Node(key);
+	}
+
+	template <typename Key, class Comparator>
+	inline SkipList<Key, Comparator>::Iterator::Iterator(const SkipList* list) {
+		list_ = list;
+		node_ = nullptr;
+	}
+
+	template <typename Key, class Comparator>
+	inline bool SkipList<Key, Comparator>::Iterator::Valid() const {
+		return node_ != nullptr;
+	}
+
+	template <typename Key, class Comparator>
+	inline const Key& SkipList<Key, Comparator>::Iterator::key() const {
+		assert(Valid());
+		return node_->key;
+	}
+
+	template <typename Key, class Comparator>
+	inline void SkipList<Key, Comparator>::Iterator::Next() {
+		assert(Valid());
+		node_ = node_->Next(0);
+	}
+
+	template <typename Key, class Comparator>
+	inline void SkipList<Key, Comparator>::Iterator::Prev() {
+		// Instead of using explicit "prev" links, we just search for the
+		// last node that falls before key.
+		assert(Valid());
+		node_ = list_->FindLessThan(node_->key);
+		if (node_ == list_->head_) {
+			node_ = nullptr;
+		}
+	}
+
+	template <typename Key, class Comparator>
+	inline void SkipList<Key, Comparator>::Iterator::Seek(const Key& target) {
+		node_ = list_->FindGreaterOrEqual(target, nullptr);
+	}
+
+	template <typename Key, class Comparator>
+	inline void SkipList<Key, Comparator>::Iterator::SeekToFirst() {
+		node_ = list_->head_->Next(0);
+	}
+
+	template <typename Key, class Comparator>
+	inline void SkipList<Key, Comparator>::Iterator::SeekToLast() {
+		node_ = list_->FindLast();
+		if (node_ == list_->head_) {
+			node_ = nullptr;
+		}
+	}
+
+	template <typename Key, class Comparator>
+	int SkipList<Key, Comparator>::RandomHeight() {
+		// Increase height with probability 1 in kBranching
+		static const unsigned int kBranching = 4;
+		int height = 1;
+		while (height < kMaxHeight && ((rnd_.Next() % kBranching) == 0)) {
+			height++;
+		}
+		assert(height > 0);
+		assert(height <= kMaxHeight);
+		return height;
+	}
+
+	template <typename Key, class Comparator>
+	bool SkipList<Key, Comparator>::KeyIsAfterNode(const Key& key, Node* n) const {
+		// null n is considered infinite
+		return (n != nullptr) && (compare_(n->key, key) < 0);
+	}
+
+	template <typename Key, class Comparator>
+	typename SkipList<Key, Comparator>::Node*
+	SkipList<Key, Comparator>::FindGreaterOrEqual(const Key& key,
+												  Node** prev) const {
+		Node* x = head_;
+		int level = GetMaxHeight() - 1;
+		while (true) {
+			Node* next = x->Next(level);
+			if (KeyIsAfterNode(key, next)) {
+				// Keep searching in this list
+				x = next;
+			} else {
+				if (prev != nullptr) prev[level] = x;
+				if (level == 0) {
+					return next;
+				} else {
+					// Switch to next list
+					level--;
+				}
+			}
+		}
+	}
+
+	template <typename Key, class Comparator>
+	typename SkipList<Key, Comparator>::Node*
+	SkipList<Key, Comparator>::FindLessThan(const Key& key) const {
+		Node* x = head_;
+		int level = GetMaxHeight() - 1;
+		while (true) {
+			assert(x == head_ || compare_(x->key, key) < 0);
+			Node* next = x->Next(level);
+			if (next == nullptr || compare_(next->key, key) >= 0) {
+				if (level == 0) {
+					return x;
+				} else {
+					// Switch to next list
+					level--;
+				}
+			} else {
+				x = next;
+			}
+		}
+	}
+
+	template <typename Key, class Comparator>
+	typename SkipList<Key, Comparator>::Node* SkipList<Key, Comparator>::FindLast()
+	const {
+		Node* x = head_;
+		int level = GetMaxHeight() - 1;
+		while (true) {
+			Node* next = x->Next(level);
+			if (next == nullptr) {
+				if (level == 0) {
+					return x;
+				} else {
+					// Switch to next list
+					level--;
+				}
+			} else {
+				x = next;
+			}
+		}
+	}
+
+	template <typename Key, class Comparator>
+	SkipList<Key, Comparator>::SkipList(Comparator cmp, Arena* arena)
+			: compare_(cmp),
+			  arena_(arena),
+			  head_(NewNode(0 /* any key will do */, kMaxHeight)),
+			  max_height_(1),
+			  rnd_(0xdeadbeef) {
+		for (int i = 0; i < kMaxHeight; i++) {
+			head_->SetNext(i, nullptr);
+		}
+	}
+
+	template <typename Key, class Comparator>
+	void SkipList<Key, Comparator>::Insert(const Key& key) {
+		// TODO(opt): We can use a barrier-free variant of FindGreaterOrEqual()
+		// here since Insert() is externally synchronized.
+		Node* prev[kMaxHeight];
+		Node* x = FindGreaterOrEqual(key, prev);
+
+		// Our data structure does not allow duplicate insertion
+		assert(x == nullptr || !Equal(key, x->key));
+
+		int height = RandomHeight();
+		if (height > GetMaxHeight()) {
+			for (int i = GetMaxHeight(); i < height; i++) {
+				prev[i] = head_;
+			}
+			// It is ok to mutate max_height_ without any synchronization
+			// with concurrent readers.  A concurrent reader that observes
+			// the new value of max_height_ will see either the old value of
+			// new level pointers from head_ (nullptr), or a new value set in
+			// the loop below.  In the former case the reader will
+			// immediately drop to the next level since nullptr sorts after all
+			// keys.  In the latter case the reader will use the new node.
+			max_height_.store(height, std::memory_order_relaxed);
+		}
+
+		x = NewNode(key, height);
+		for (int i = 0; i < height; i++) {
+			// NoBarrier_SetNext() suffices since we will add a barrier when
+			// we publish a pointer to "x" in prev[i].
+			x->NoBarrier_SetNext(i, prev[i]->NoBarrier_Next(i));
+			prev[i]->SetNext(i, x);
+		}
+	}
+
+	template <typename Key, class Comparator>
+	bool SkipList<Key, Comparator>::Contains(const Key& key) const {
+		Node* x = FindGreaterOrEqual(key, nullptr);
+		if (x != nullptr && Equal(key, x->key)) {
+			return true;
+		} else {
+			return false;
+		}
+	}
+
+}  // namespace cleveldb
+#endif //CLEVELDB_SKIPLIST_CUH