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Diffstat (limited to 'src/lmdb/util.h')
| -rw-r--r-- | src/lmdb/util.h | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/src/lmdb/util.h b/src/lmdb/util.h new file mode 100644 index 000000000..50162b7c8 --- /dev/null +++ b/src/lmdb/util.h @@ -0,0 +1,149 @@ +// Copyright (c) 2018, 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 |