raw: Add the ability to extract references to data in buffers
Change-Id: If3de6cfbc63e4a826f60f9f56c2e1ad533e62441
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/src/stdplus/raw.hpp b/src/stdplus/raw.hpp
index aaf803e..f6938e2 100644
--- a/src/stdplus/raw.hpp
+++ b/src/stdplus/raw.hpp
@@ -69,6 +69,27 @@
return ret;
}
+/** @brief References the data from a buffer if aligned
+ *
+ * @param[in] data - The data buffer being referenced
+ * @return The reference to the data in the new type
+ */
+template <typename T, typename Container,
+ typename Tp = detail::copyConst<T, detail::dataType<Container>>>
+Tp& refFrom(Container& c)
+{
+ static_assert(std::is_trivially_copyable_v<Tp>);
+ static_assert(detail::trivialContainer<Container>);
+ static_assert(sizeof(*std::data(c)) % alignof(Tp) == 0);
+ const size_t bytes = std::size(c) * sizeof(*std::data(c));
+ if (bytes < sizeof(Tp))
+ {
+ throw std::runtime_error(
+ fmt::format("RefFrom: {} < {}", bytes, sizeof(Tp)));
+ }
+ return *reinterpret_cast<Tp*>(std::data(c));
+}
+
/** @brief Extracts data from a buffer into a copyable type
* Updates the data buffer to show that data was removed
*
@@ -95,6 +116,33 @@
}
#endif
+/** @brief Extracts data from a buffer as a reference if aligned
+ * Updates the data buffer to show that data was removed
+ *
+ * @param[in,out] data - The data buffer being extracted from
+ * @return A reference to the data
+ */
+template <typename T, typename CharT>
+const T& extractRef(std::basic_string_view<CharT>& data)
+{
+ const T& ret = refFrom<T>(data);
+ static_assert(sizeof(T) % sizeof(CharT) == 0);
+ data.remove_prefix(sizeof(T) / sizeof(CharT));
+ return ret;
+}
+#ifdef STDPLUS_SPAN_TYPE
+template <typename T, typename IntT,
+ typename = std::enable_if_t<std::is_trivially_copyable_v<IntT>>,
+ typename Tp = detail::copyConst<T, IntT>>
+Tp& extractRef(span<IntT>& data)
+{
+ Tp& ret = refFrom<Tp>(data);
+ static_assert(sizeof(Tp) % sizeof(IntT) == 0);
+ data = data.subspan(sizeof(Tp) / sizeof(IntT));
+ return ret;
+}
+#endif
+
/** @brief Returns the span referencing the data of the raw trivial type
* or of trivial types in a contiguous container.
*
diff --git a/test/raw.cpp b/test/raw.cpp
index fd8ae71..8be8b7b 100644
--- a/test/raw.cpp
+++ b/test/raw.cpp
@@ -23,9 +23,10 @@
TEST_CASE("Copy From Empty", "[CopyFrom]")
{
- const std::string_view s;
+ const std::string_view cs;
+ CHECK_THROWS_AS(copyFrom<int>(cs), std::runtime_error);
+ std::string_view s;
CHECK_THROWS_AS(copyFrom<int>(s), std::runtime_error);
- CHECK(s.empty());
}
TEST_CASE("Copy From Basic", "[CopyFrom]")
@@ -43,6 +44,39 @@
CHECK('d' == copyFrom<char>(s2));
}
+struct Int
+{
+ uint8_t data[sizeof(int)];
+
+ inline bool operator==(const Int& other) const
+ {
+ return memcmp(data, other.data, sizeof(data)) == 0;
+ }
+};
+
+TEST_CASE("Ref From Empty", "[RefFrom]")
+{
+ const std::string_view cs;
+ CHECK_THROWS_AS(refFrom<Int>(cs), std::runtime_error);
+ std::string_view s;
+ CHECK_THROWS_AS(refFrom<Int>(s), std::runtime_error);
+}
+
+TEST_CASE("Ref From Basic", "[RefFrom]")
+{
+ Int a = {4, 0, 0, 4};
+ const std::string_view s(reinterpret_cast<char*>(&a), sizeof(a));
+ CHECK(a == refFrom<Int>(s));
+}
+
+TEST_CASE("Ref From Partial", "[RefFrom]")
+{
+ const std::vector<char> s = {'a', 'b', 'c'};
+ CHECK('a' == refFrom<char>(s));
+ const char s2[] = "def";
+ CHECK('d' == refFrom<char>(s2));
+}
+
TEST_CASE("Extract Too Small", "[Extract]")
{
std::string_view s("a");
@@ -65,6 +99,28 @@
CHECK(2 == s.size());
}
+TEST_CASE("Extract Ref Too Small", "[ExtractRef]")
+{
+ std::string_view s("a");
+ CHECK_THROWS_AS(extractRef<Int>(s), std::runtime_error);
+ CHECK(1 == s.size());
+}
+
+TEST_CASE("Extract Ref Basic", "[ExtractRef]")
+{
+ Int a = {4, 0, 0, 4};
+ std::string_view s(reinterpret_cast<char*>(&a), sizeof(a));
+ CHECK(a == extractRef<Int>(s));
+ CHECK(s.empty());
+}
+
+TEST_CASE("Extract Ref Partial", "[ExtractRef]")
+{
+ std::string_view s("abc");
+ CHECK('a' == extractRef<char>(s));
+ CHECK(2 == s.size());
+}
+
TEST_CASE("As View Byte", "[AsView]")
{
int32_t a = 4;
@@ -115,6 +171,30 @@
CHECK(v.size() - 1 == s.size());
}
+TEST_CASE("Span Extract Ref TooSmall", "[ExtractRef]")
+{
+ const std::vector<char> v = {'c'};
+ span<const char> s = v;
+ CHECK_THROWS_AS(extractRef<Int>(s), std::runtime_error);
+ CHECK(1 == s.size());
+}
+
+TEST_CASE("Span Extract Ref Basic", "[ExtractRef]")
+{
+ const std::vector<Int> v = {{4, 0, 0, 4}};
+ span<const Int> s = v;
+ CHECK(v[0] == extractRef<Int>(s));
+ CHECK(s.empty());
+}
+
+TEST_CASE("Span Extract Ref Larger", "[ExtractRef]")
+{
+ const std::vector<Int> v{{3}, {4}, {5}};
+ span<const Int> s = v;
+ CHECK(v[0] == extractRef<Int>(s));
+ CHECK(v.size() - 1 == s.size());
+}
+
TEST_CASE("As Span const", "[AsSpan]")
{
const uint64_t data = htole64(0xffff0000);