dtc/src/libs/common/file_backed_key_set.h

/*
* Copyright [2021] JD.com, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
*     http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef FILE_BACKED_KEY_SET_H__
#define FILE_BACKED_KEY_SET_H__

#include <unistd.h>

#include <stdint.h>
#include <string>
#include <vector>

#define MIGRATE_START 1
#define MIGRATE_SUCCESS 2

class FileBackedKeySet {
    public:
	FileBackedKeySet(const char *file, int keySize);
	~FileBackedKeySet();

	bool Contains(const char *key, bool checkStatus = true);
	bool is_migrating(const char *key);
	int Open();
	int Load();
	int do_insert(const char *key);
	int Migrated(const char *key);
	void Clear();

    private:
	struct hash_node {
		hash_node *next;
		uintptr_t offset;
	};

	class hash_node_allocator {
	    public:
		hash_node_allocator() : m_freeNode(NULL)
		{
		}
		~hash_node_allocator();

		hash_node *alloc();
		void free(hash_node *n);
		void reset();

		static const int GROW_COUNT = 4096 * 16;

	    private:
		hash_node *m_freeNode;
		std::vector<char *> m_buffs;
	};

	hash_node_allocator m_allocator;

	struct meta_info {
		uintptr_t size;
		uintptr_t writePos;
	};

	//4M
	static const int INIT_FILE_SIZE = 4096 * 1024;
	static const int GROW_FILE_SIZE = 1024 * 1024;
	static const int BUCKET_SIZE = 1024 * 1024;

	meta_info *get_meta_info()
	{
		return (meta_info *)m_base;
	}
	void insert_to_set(const char *key, int len);
	char *insert_to_file(const char *key, int len);

	std::string m_filePath;
	int m_fd;
	int m_keySize;
	char *m_base;
	hash_node **m_buckets;
};

#endif