The legacy read-only database adapter contract

1// Copyright (c) 2021-present The Bitcoin Core developers
2// Distributed under the MIT software license, see the accompanying
3// file COPYING or http://www.opensource.org/licenses/mit-license.php.
4
5#ifndef BITCOIN_WALLET_MIGRATE_H
6#define BITCOIN_WALLET_MIGRATE_H
7
8#include <wallet/db.h>
9
10#include <optional>
11
12namespace wallet {
13
14using BerkeleyROData = std::map<SerializeData, SerializeData, std::less<>>;
15
16/**
17 * A class representing a BerkeleyDB file from which we can only read records.
18 * This is used only for migration of legacy to descriptor wallets
19 */
20class BerkeleyRODatabase : public WalletDatabase
21{
22private:
23    const fs::path m_filepath;
24
25public:
26    /** Create DB handle */
27    BerkeleyRODatabase(const fs::path& filepath, bool open = true) : WalletDatabase(), m_filepath(filepath)
28    {
29        if (open) Open();
30    }
31    ~BerkeleyRODatabase() = default;
32
33    BerkeleyROData m_records;
34
35    /** Open the database if it is not already opened. */
36    void Open() override;
37
38    /** Rewrite the entire database on disk
39     */
40    bool Rewrite() override { return false; }
41
42    /** Back up the entire database to a file.
43     */
44    bool Backup(const std::string& strDest) const override;
45
46    /** Flush to the database file and close the database.
47     *  Also close the environment if no other databases are open in it.
48     */
49    void Close() override {}
50
51    /** Return path to main database file for logs and error messages. */
52    std::string Filename() override { return fs::PathToString(m_filepath); }
53    std::vector<fs::path> Files() override { return {m_filepath}; }
54
55    std::string Format() override { return "bdb_ro"; }
56
57    /** Make a DatabaseBatch connected to this database */
58    std::unique_ptr<DatabaseBatch> MakeBatch() override;
59};
60
61class BerkeleyROCursor : public DatabaseCursor
62{
63private:
64    const BerkeleyRODatabase& m_database;
65    BerkeleyROData::const_iterator m_cursor;
66    BerkeleyROData::const_iterator m_cursor_end;
67
68public:
69    explicit BerkeleyROCursor(const BerkeleyRODatabase& database, std::span<const std::byte> prefix = {});
70    ~BerkeleyROCursor() = default;
71
72    Status Next(DataStream& key, DataStream& value) override;
73};
74
75/** RAII class that provides access to a BerkeleyRODatabase */
76class BerkeleyROBatch : public DatabaseBatch
77{
78private:
79    const BerkeleyRODatabase& m_database;
80
81    bool ReadKey(DataStream&& key, DataStream& value) override;
82    // WriteKey returns true since various automatic upgrades for older wallets will expect writing to not fail.
83    // It is okay for this batch type to not actually write anything as those automatic upgrades will occur again after migration.
84    bool WriteKey(DataStream&& key, DataStream&& value, bool overwrite = true) override { return true; }
85    bool EraseKey(DataStream&& key) override { return false; }
86    bool HasKey(DataStream&& key) override;
87    bool ErasePrefix(std::span<const std::byte> prefix) override { return false; }
88
89public:
90    explicit BerkeleyROBatch(const BerkeleyRODatabase& database) : m_database(database) {}
91    ~BerkeleyROBatch() = default;
92
93    BerkeleyROBatch(const BerkeleyROBatch&) = delete;
94    BerkeleyROBatch& operator=(const BerkeleyROBatch&) = delete;
95
96    void Close() override {}
97
98    std::unique_ptr<DatabaseCursor> GetNewCursor() override { return std::make_unique<BerkeleyROCursor>(m_database); }
99    std::unique_ptr<DatabaseCursor> GetNewPrefixCursor(std::span<const std::byte> prefix) override;
100    bool TxnBegin() override { return false; }
101    bool TxnCommit() override { return false; }
102    bool TxnAbort() override { return false; }
103    bool HasActiveTxn() override { return false; }
104};
105
106//! Return object giving access to Berkeley Read Only database at specified path.
107std::unique_ptr<BerkeleyRODatabase> MakeBerkeleyRODatabase(const fs::path& path, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);
108} // namespace wallet
109
110#endif // BITCOIN_WALLET_MIGRATE_H
111