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// Copyright (c) 2018-2024, The Monero Project
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#pragma once
#include <cstddef>
#include <cstring>
#include <lmdb.h>
#include <type_traits>
#include <utility>
#include "span.h"
/*! Calculates types and offset of struct field. Use in template arguments for
`table::get_value`, `value_iterator::get_value`,
`value_stream::make_iterator`, or `value_stream::make_range`. */
#define MONERO_FIELD(obj, field) \
obj , decltype(std::declval<obj>().field) , offsetof(obj, field)
//! Expands to `lmdb::less` for the value `field` within `obj`.
#define MONERO_SORT_BY(obj, field) \
&::lmdb::less< \
lmdb::native_type<decltype(std::declval<obj>().field)>, \
offsetof(obj, field) \
>
//! Expands to `lmdb::compare` for the value `field` within `obj`.
#define MONERO_COMPARE(obj, field) \
&::lmdb::compare< \
decltype(std::declval<obj>().field), \
offsetof(obj, field) \
>
namespace lmdb
{
//! Prevent instantiation of `std::underlying_type<T>` when `T` is not enum.
template<typename T>
struct identity
{
using type = T;
};
/*!
Get the native type for enums, or return `T` unchanged. Useful for
merging generated machine code for templated functions that use enums
with identical size-widths without relying on aggressive identical
comdat folding (ICF) support in linker. So with enum defintion
`enum class enum_foo : unsigned long {};` will always yield
`assert(&func_foo<unsigned long> == &func_foo<native_type<enum_foo>>)`.
*/
template<typename T>
using native_type = typename std::conditional<
std::is_enum<T>::value, std::underlying_type<T>, identity<T>
>::type::type;
//! \return `value` as its native type.
template<typename T, typename U = typename std::underlying_type<T>::type>
inline constexpr U to_native(T value) noexcept
{
return U(value);
}
//! \return `value` bytes in a LMDB `MDB_val` object.
template<typename T>
inline MDB_val to_val(T&& value) noexcept
{
// lmdb does not touch user data, so const_cast is acceptable
static_assert(!std::is_rvalue_reference<T&&>(), "cannot use temporary value");
void const* const temp = reinterpret_cast<void const*>(std::addressof(value));
return MDB_val{sizeof(value), const_cast<void*>(temp)};
}
//! \return A span over the same chunk of memory as `value`.
inline constexpr epee::span<const std::uint8_t> to_byte_span(MDB_val value) noexcept
{
return {static_cast<const std::uint8_t*>(value.mv_data), value.mv_size};
}
/*!
A LMDB comparison function that uses `operator<`.
\tparam T has a defined `operator<` .
\tparam offset to `T` within the value.
\return -1 if `left < right`, 1 if `right < left`, and 0 otherwise.
*/
template<typename T, std::size_t offset = 0>
inline int less(MDB_val const* left, MDB_val const* right) noexcept
{
if (!left || !right || left->mv_size < sizeof(T) + offset || right->mv_size < sizeof(T) + offset)
{
assert("invalid use of custom comparison" == 0);
return -1;
}
T left_val;
T right_val;
std::memcpy(std::addressof(left_val), static_cast<char*>(left->mv_data) + offset, sizeof(T));
std::memcpy(std::addressof(right_val), static_cast<char*>(right->mv_data) + offset, sizeof(T));
return left_val < right_val ? -1 : bool(right_val < left_val);
}
/*!
A LMDB comparison function that uses `std::memcmp`.
\toaram T is `!epee::has_padding`
\tparam offset to `T` within the value.
\return The result of `std::memcmp` over the value.
*/
template<typename T, std::size_t offset = 0>
inline int compare(MDB_val const* left, MDB_val const* right) noexcept
{
static_assert(!epee::has_padding<T>(), "memcmp will not work");
if (!left || !right || left->mv_size < sizeof(T) + offset || right->mv_size < sizeof(T) + offset)
{
assert("invalid use of custom comparison" == 0);
return -1;
}
return std::memcmp(
static_cast<char*>(left->mv_data) + offset,
static_cast<char*>(right->mv_data) + offset,
sizeof(T)
);
}
} // lmdb
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