Merge "FTL: Allow Concat of bool and char" (a81a627c) · Commits · e / os / android_frameworks_native

include/ftl/concat.h

+3 −1

Original line number	Diff line number	Diff line
		@@ -20,7 +20,9 @@

		namespace android::ftl {

		// Lightweight (not allocating nor sprintf-based) concatenation.
		// Lightweight (not allocating nor sprintf-based) concatenation. The variadic arguments can be
		// values of integral type (including bool and char), string literals, or strings whose length
		// is constrained:
		//
		// std::string_view name = "Volume";
		// ftl::Concat string(ftl::truncated<3>(name), ": ", -3, " dB");

include/ftl/details/concat.h

+32 −4

Original line number	Diff line number	Diff line
		@@ -19,6 +19,7 @@
		#include <functional>
		#include <string_view>

		#include <ftl/details/type_traits.h>
		#include <ftl/string.h>

		namespace android::ftl::details {
		@@ -26,16 +27,42 @@ namespace android::ftl::details {
		template <typename T, typename = void>
		struct StaticString;

		// Booleans.
		template <typename T>
		struct StaticString<T, std::enable_if_t<std::is_integral_v<T>>> {
		static constexpr std::size_t N = to_chars_length_v<T>;
		struct StaticString<T, std::enable_if_t<is_bool_v<T>>> {
		static constexpr std::size_t N = 5; // Length of "false".

		explicit StaticString(T v) : view(to_chars(buffer, v)) {}
		explicit constexpr StaticString(bool b) : view(b ? "true" : "false") {}

		to_chars_buffer_t<T> buffer;
		const std::string_view view;
		};

		// Characters.
		template <typename T>
		struct StaticString<T, std::enable_if_t<is_char_v<T>>> {
		static constexpr std::size_t N = 1;

		explicit constexpr StaticString(char c) : character(c) {}

		const char character;
		const std::string_view view{&character, 1u};
		};

		// Integers, including the integer value of other character types like char32_t.
		template <typename T>
		struct StaticString<
		T, std::enable_if_t<std::is_integral_v<remove_cvref_t<T>> && !is_bool_v<T> && !is_char_v<T>>> {
		using U = remove_cvref_t<T>;
		static constexpr std::size_t N = to_chars_length_v<U>;

		// TODO: Mark this and to_chars as `constexpr` in C++23.
		explicit StaticString(U v) : view(to_chars(buffer, v)) {}

		to_chars_buffer_t<U> buffer;
		const std::string_view view;
		};

		// Character arrays.
		template <std::size_t M>
		struct StaticString<const char (&)[M], void> {
		static constexpr std::size_t N = M - 1;
		@@ -50,6 +77,7 @@ struct Truncated {
		std::string_view view;
		};

		// Strings with constrained length.
		template <std::size_t M>
		struct StaticString<Truncated<M>, void> {
		static constexpr std::size_t N = M;

include/ftl/details/type_traits.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -24,4 +24,10 @@ namespace android::ftl::details {
		template <typename U>
		using remove_cvref_t = std::remove_cv_t<std::remove_reference_t<U>>;

		template <typename T>
		constexpr bool is_bool_v = std::is_same_v<remove_cvref_t<T>, bool>;

		template <typename T>
		constexpr bool is_char_v = std::is_same_v<remove_cvref_t<T>, char>;

		} // namespace android::ftl::details

libs/ftl/concat_test.cpp

+17 −0

Original line number	Diff line number	Diff line
		@@ -28,8 +28,25 @@ TEST(Concat, Example) {
		EXPECT_EQ(string.c_str()[string.size()], '\0');
		}

		TEST(Concat, Characters) {
		EXPECT_EQ(ftl::Concat(u'a', ' ', U'b').str(), "97 98");
		}

		TEST(Concat, References) {
		int i[] = {-1, 2};
		unsigned u = 3;
		EXPECT_EQ(ftl::Concat(i[0], std::as_const(i[1]), u).str(), "-123");

		const bool b = false;
		const char c = 'o';
		EXPECT_EQ(ftl::Concat(b, "tt", c).str(), "falsetto");
		}

		namespace {

		static_assert(ftl::Concat{true, false, true}.str() == "truefalsetrue");
		static_assert(ftl::Concat{':', '-', ')'}.str() == ":-)");

		static_assert(ftl::Concat{"foo"}.str() == "foo");
		static_assert(ftl::Concat{ftl::truncated<3>("foobar")}.str() == "foo");