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https://github.com/monero-project/monero.git
synced 2024-10-01 11:49:47 -04:00
Added features to epee::span<T> :
- Support for classes - Added `remove_prefix` function - Added `to_mut_span` and `as_mut_byte_span`
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@ -28,6 +28,7 @@
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#pragma once
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#include <algorithm>
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#include <cstdint>
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#include <memory>
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#include <type_traits>
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@ -52,11 +53,15 @@ namespace epee
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template<typename T>
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class span
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{
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/* Supporting class types is tricky - the {ptr,len} constructor will allow
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derived-to-base conversions. This is NOT desireable because an array of
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derived types is not an array of base types. It is possible to handle
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this case, implement when/if needed. */
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static_assert(!std::is_class<T>(), "no class types are currently allowed");
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template<typename U>
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static constexpr bool safe_conversion() noexcept
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{
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// Allow exact matches or `T*` -> `const T*`.
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using with_const = typename std::add_const<U>::type;
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return std::is_same<T, U>() ||
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(std::is_const<T>() && std::is_same<T, with_const>());
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}
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public:
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using value_type = T;
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using size_type = std::size_t;
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@ -71,7 +76,9 @@ namespace epee
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constexpr span() noexcept : ptr(nullptr), len(0) {}
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constexpr span(std::nullptr_t) noexcept : span() {}
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constexpr span(T* const src_ptr, const std::size_t count) noexcept
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//! Prevent derived-to-base conversions; invalid in this context.
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template<typename U, typename = typename std::enable_if<safe_conversion<U>()>::type>
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constexpr span(U* const src_ptr, const std::size_t count) noexcept
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: ptr(src_ptr), len(count) {}
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//! Conversion from C-array. Prevents common bugs with sizeof + arrays.
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@ -81,6 +88,16 @@ namespace epee
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constexpr span(const span&) noexcept = default;
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span& operator=(const span&) noexcept = default;
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/*! Try to remove `amount` elements from beginning of span.
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\return Number of elements removed. */
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std::size_t remove_prefix(std::size_t amount) noexcept
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{
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amount = std::min(len, amount);
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ptr += amount;
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len -= amount;
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return amount;
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}
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constexpr iterator begin() const noexcept { return ptr; }
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constexpr const_iterator cbegin() const noexcept { return ptr; }
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@ -105,6 +122,14 @@ namespace epee
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return {src.data(), src.size()};
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}
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//! \return `span<T::value_type>` from a STL compatible `src`.
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template<typename T>
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constexpr span<typename T::value_type> to_mut_span(T& src)
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{
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// compiler provides diagnostic if size() is not size_t.
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return {src.data(), src.size()};
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}
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template<typename T>
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constexpr bool has_padding() noexcept
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{
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@ -127,4 +152,13 @@ namespace epee
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static_assert(!has_padding<T>(), "source type may have padding");
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return {reinterpret_cast<const std::uint8_t*>(std::addressof(src)), sizeof(T)};
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}
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//! \return `span<std::uint8_t>` which represents the bytes at `&src`.
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template<typename T>
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span<std::uint8_t> as_mut_byte_span(T& src) noexcept
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{
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static_assert(!std::is_empty<T>(), "empty types will not work -> sizeof == 1");
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static_assert(!has_padding<T>(), "source type may have padding");
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return {reinterpret_cast<std::uint8_t*>(std::addressof(src)), sizeof(T)};
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}
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}
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@ -166,12 +166,17 @@ TEST(Span, Traits)
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TEST(Span, MutableConstruction)
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{
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struct no_conversion{};
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struct inherited : no_conversion {};
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EXPECT_TRUE(std::is_constructible<epee::span<char>>());
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EXPECT_TRUE((std::is_constructible<epee::span<char>, char*, std::size_t>()));
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EXPECT_FALSE((std::is_constructible<epee::span<char>, const char*, std::size_t>()));
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EXPECT_FALSE((std::is_constructible<epee::span<char>, unsigned char*, std::size_t>()));
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EXPECT_TRUE(std::is_constructible<epee::span<no_conversion>>());
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EXPECT_TRUE((std::is_constructible<epee::span<no_conversion>, no_conversion*, std::size_t>()));
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EXPECT_FALSE((std::is_constructible<epee::span<no_conversion>, inherited*, std::size_t>()));
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EXPECT_TRUE((can_construct<epee::span<char>, std::nullptr_t>()));
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EXPECT_TRUE((can_construct<epee::span<char>, char(&)[1]>()));
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@ -193,12 +198,19 @@ TEST(Span, MutableConstruction)
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TEST(Span, ImmutableConstruction)
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{
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struct no_conversion{};
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struct inherited : no_conversion {};
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EXPECT_TRUE(std::is_constructible<epee::span<const char>>());
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EXPECT_TRUE((std::is_constructible<epee::span<const char>, char*, std::size_t>()));
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EXPECT_TRUE((std::is_constructible<epee::span<const char>, const char*, std::size_t>()));
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EXPECT_FALSE((std::is_constructible<epee::span<const char>, unsigned char*, std::size_t>()));
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EXPECT_TRUE(std::is_constructible<epee::span<const no_conversion>>());
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EXPECT_TRUE((std::is_constructible<epee::span<const no_conversion>, const no_conversion*, std::size_t>()));
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EXPECT_TRUE((std::is_constructible<epee::span<const no_conversion>, no_conversion*, std::size_t>()));
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EXPECT_FALSE((std::is_constructible<epee::span<const no_conversion>, const inherited*, std::size_t>()));
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EXPECT_FALSE((std::is_constructible<epee::span<const no_conversion>, inherited*, std::size_t>()));
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EXPECT_FALSE((can_construct<epee::span<const char>, std::string>()));
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EXPECT_FALSE((can_construct<epee::span<const char>, std::vector<char>>()));
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EXPECT_FALSE((can_construct<epee::span<const char>, const std::vector<char>>()));
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@ -231,7 +243,6 @@ TEST(Span, NoExcept)
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const epee::span<char> clvalue(data);
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EXPECT_TRUE(noexcept(epee::span<char>()));
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EXPECT_TRUE(noexcept(epee::span<char>(nullptr)));
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EXPECT_TRUE(noexcept(epee::span<char>(nullptr, 0)));
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EXPECT_TRUE(noexcept(epee::span<char>(data)));
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EXPECT_TRUE(noexcept(epee::span<char>(lvalue)));
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EXPECT_TRUE(noexcept(epee::span<char>(clvalue)));
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@ -284,6 +295,25 @@ TEST(Span, Writing)
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EXPECT_TRUE(boost::range::equal(expected, span));
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}
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TEST(Span, RemovePrefix)
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{
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const std::array<unsigned, 4> expected{0, 1, 2, 3};
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auto span = epee::to_span(expected);
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EXPECT_EQ(expected.begin(), span.begin());
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EXPECT_EQ(expected.end(), span.end());
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EXPECT_EQ(2u, span.remove_prefix(2));
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EXPECT_EQ(expected.begin() + 2, span.begin());
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EXPECT_EQ(expected.end(), span.end());
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EXPECT_EQ(2u, span.remove_prefix(3));
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EXPECT_EQ(span.begin(), span.end());
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EXPECT_EQ(expected.end(), span.begin());
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EXPECT_EQ(0u, span.remove_prefix(100));
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}
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TEST(Span, ToByteSpan)
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{
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const char expected[] = {56, 44, 11, 5};
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@ -318,6 +348,30 @@ TEST(Span, AsByteSpan)
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);
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}
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TEST(Span, AsMutByteSpan)
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{
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struct some_pod { char value[4]; };
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some_pod actual {};
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auto span = epee::as_mut_byte_span(actual);
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boost::range::iota(span, 1);
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EXPECT_TRUE(
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boost::range::equal(
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std::array<unsigned char, 4>{{1, 2, 3, 4}}, actual.value
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)
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);
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}
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TEST(Span, ToMutSpan)
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{
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std::vector<unsigned> mut;
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mut.resize(4);
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auto span = epee::to_mut_span(mut);
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boost::range::iota(span, 1);
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EXPECT_EQ((std::vector<unsigned>{1, 2, 3, 4}), mut);
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}
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TEST(ToHex, String)
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{
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EXPECT_TRUE(epee::to_hex::string(nullptr).empty());
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@ -330,6 +384,7 @@ TEST(ToHex, String)
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EXPECT_EQ(
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std_to_hex(all_bytes), epee::to_hex::string(epee::to_span(all_bytes))
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);
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}
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TEST(ToHex, Array)
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