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121 lines
4.1 KiB
121 lines
4.1 KiB
#pragma once
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#include <utility>
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#include "common/expect.h"
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#include "lmdb/error.h"
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#include "lmdb/key_stream.h"
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#include "lmdb/util.h"
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#include "lmdb/value_stream.h"
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namespace lmdb
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{
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//! Helper for grouping typical LMDB DBI options.
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struct table
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{
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char const* const name;
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const unsigned flags;
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MDB_cmp_func* const key_cmp;
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MDB_cmp_func* const value_cmp;
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//! \pre `name != nullptr` \return Open table.
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expect<MDB_dbi> open(MDB_txn& write_txn) const noexcept;
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};
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//! Helper for grouping typical LMDB DBI options when key and value are fixed types.
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template<typename K, typename V>
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struct basic_table : table
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{
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using key_type = K;
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using value_type = V;
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//! \return Additional LMDB flags based on `flags` value.
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static constexpr unsigned compute_flags(const unsigned flags) noexcept
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{
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return flags | ((flags & MDB_DUPSORT) ? MDB_DUPFIXED : 0);
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}
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constexpr explicit basic_table(const char* name, unsigned flags = 0, MDB_cmp_func value_cmp = nullptr) noexcept
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: table{name, compute_flags(flags), &lmdb::less<lmdb::native_type<K>>, value_cmp}
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{}
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/*!
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\tparam U must be same as `V`; used for sanity checking.
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\tparam F is the type within `U` that is being extracted.
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\tparam offset to `F` within `U`.
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\note If using `F` and `offset` to retrieve a specific field, use
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`MONERO_FIELD` macro in `src/lmdb/util.h` which calculates the
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offset automatically.
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\return Value of type `F` at `offset` within `value` which has
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type `U`.
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*/
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template<typename U, typename F = U, std::size_t offset = 0>
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static expect<F> get_value(MDB_val value) noexcept
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{
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static_assert(std::is_same<U, V>(), "bad MONERO_FIELD?");
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static_assert(std::is_pod<F>(), "F must be POD");
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static_assert(sizeof(F) + offset <= sizeof(U), "bad field type and/or offset");
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if (value.mv_size != sizeof(U))
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return {lmdb::error(MDB_BAD_VALSIZE)};
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F out;
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std::memcpy(std::addressof(out), static_cast<char*>(value.mv_data) + offset, sizeof(out));
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return out;
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}
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/*!
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\pre `cur != nullptr`.
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\param cur Active cursor on table. Returned in object on success,
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otherwise destroyed.
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\return A handle to the first key/value in the table linked
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to `cur` or an empty `key_stream`.
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*/
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template<typename D>
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expect<key_stream<K, V, D>>
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static get_key_stream(std::unique_ptr<MDB_cursor, D> cur) noexcept
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{
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MONERO_PRECOND(cur != nullptr);
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MDB_val key;
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MDB_val value;
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const int err = mdb_cursor_get(cur.get(), &key, &value, MDB_FIRST);
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if (err)
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{
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if (err != MDB_NOTFOUND)
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return {lmdb::error(err)};
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cur.reset(); // return empty set
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}
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return key_stream<K, V, D>{std::move(cur)};
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}
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/*!
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\pre `cur != nullptr`.
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\param cur Active cursor on table. Returned in object on success,
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otherwise destroyed.
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\return A handle to the first value at `key` in the table linked
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to `cur` or an empty `value_stream`.
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*/
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template<typename D>
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expect<value_stream<V, D>>
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static get_value_stream(K const& key, std::unique_ptr<MDB_cursor, D> cur) noexcept
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{
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MONERO_PRECOND(cur != nullptr);
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MDB_val key_bytes = lmdb::to_val(key);
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MDB_val value;
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const int err = mdb_cursor_get(cur.get(), &key_bytes, &value, MDB_SET);
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if (err)
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{
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if (err != MDB_NOTFOUND)
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return {lmdb::error(err)};
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cur.reset(); // return empty set
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}
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return value_stream<V, D>{std::move(cur)};
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}
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};
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} // lmdb
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