add span type

6 files changed, 109 insertions, 28 deletions

diff --git a/lib/nes/common/CMakeLists.txt b/lib/nes/common/CMakeLists.txt
index f0ee288..a7c1d76 100644
--- a/lib/nes/common/CMakeLists.txt
+++ b/lib/nes/common/CMakeLists.txt
@@ -12,4 +12,5 @@ target_sources(
 		path-view.hh
 		path-view.cc
 		path-builder.hh
-		path-builder.cc)
\ No newline at end of file
+		path-builder.cc
+		span.hh)
\ No newline at end of file
diff --git a/lib/nes/common/path-builder.cc b/lib/nes/common/path-builder.cc
index 67190dc..794d565 100644
--- a/lib/nes/common/path-builder.cc
+++ b/lib/nes/common/path-builder.cc
@@ -2,12 +2,11 @@
 
 namespace nes
 {
-	path_builder::path_builder(char* buffer, u32 const buffer_length)
+	path_builder::path_builder(span<char> const buffer)
 		: buffer_{ buffer }
-		, buffer_length_{ buffer_length }
 	{
 		// Initialize the path to "/" if possible.
-		if (buffer_length > 0) { buffer_[actual_length_++] = '/'; }
+		if (buffer_.get_length() > 0) { buffer_[length_++] = '/'; }
 	}
 
 	auto path_builder::push(std::string_view component) -> bool
@@ -18,30 +17,30 @@ namespace nes
 		if (component.empty() || std::find(component.begin(), component.end(), '/') != component.end()) { return false; }
 
 		// Check if there is enough remaining capacity for "/<component>"
-		auto const add_leading_slash = actual_length_ == 0 || buffer_[actual_length_ - 1] != '/';
+		auto const add_leading_slash = length_ == 0 || buffer_[length_ - 1] != '/';
 		auto const length = component.length() + (add_leading_slash ? 1 : 0);
-		if (actual_length_ + length > buffer_length_) { return false; }
+		if (length_ + length > buffer_.get_length()) { return false; }
 
 		// Append "/<component>"
-		if (add_leading_slash) { buffer_[actual_length_++] = '/'; }
-		for (auto i = u32{ 0 }; i < component.length(); ++i) { buffer_[actual_length_++] = component[i]; }
+		if (add_leading_slash) { buffer_[length_++] = '/'; }
+		for (auto i = u32{ 0 }; i < component.length(); ++i) { buffer_[length_++] = component[i]; }
 
 		return true;
 	}
 
 	auto path_builder::pop() -> bool
 	{
-		if (actual_length_ == 0 || buffer_[actual_length_ - 1] == '/') { return false; }
+		if (length_ == 0 || buffer_[length_ - 1] == '/') { return false; }
 
 		// Find the start of the last component.
-		auto last_start = actual_length_ - 1;
+		auto last_start = length_ - 1;
 		while (last_start > 0 && buffer_[last_start] != '/') { last_start -= 1; }
 
 		// Drop the slash if we are not at the root.
 		if (last_start == 0) { last_start += 1; }
 
 		// Drop everything including the trailing slash.
-		actual_length_ = last_start;
+		length_ = last_start;
 		return true;
 	}
 } // namespace nes
\ No newline at end of file
diff --git a/lib/nes/common/path-builder.hh b/lib/nes/common/path-builder.hh
index 727d18c..b64fb28 100644
--- a/lib/nes/common/path-builder.hh
+++ b/lib/nes/common/path-builder.hh
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "nes/common/types.hh"
+#include "nes/common/span.hh"
 #include "nes/common/path-view.hh"
 #include <string_view>
 
@@ -9,15 +10,14 @@ namespace nes
 	/// A mutable path with a fixed-length buffer.
 	class path_builder
 	{
-		char* buffer_{ nullptr };
-		u32 buffer_length_{ 0 };
-		u32 actual_length_{ 0 };
+		span<char> buffer_;
+		u32 length_{ 0 };
 
 	public:
-		explicit path_builder(char* buffer, u32 buffer_length);
+		explicit path_builder(span<char>);
 
 		auto get_components() const -> path_view { return path_view{ get_path() }; }
-		auto get_path() const -> std::string_view { return std::string_view{ buffer_, actual_length_ }; }
+		auto get_path() const -> std::string_view { return std::string_view{ buffer_.get_data(), length_ }; }
 
 		auto push(std::string_view) -> bool;
 		auto pop() -> bool;
@@ -31,7 +31,7 @@ namespace nes
 
 	public:
 		explicit path_buffer()
-			: path_builder{ buffer_, Capacity }
+			: path_builder{ buffer_ }
 		{
 		}
 	};
diff --git a/lib/nes/common/span.hh b/lib/nes/common/span.hh
new file mode 100644
index 0000000..16eb129
--- /dev/null
+++ b/lib/nes/common/span.hh
@@ -0,0 +1,82 @@
+#pragma once
+
+#include "nes/common/types.hh"
+
+namespace nes
+{
+	namespace detail
+	{
+		struct span_unchecked{};
+
+		inline constexpr auto span_dynamic_length = u32{ 0xFFFF };
+
+		template<typename T>
+		struct remove_const
+		{
+			using type = T;
+		};
+
+		template<typename T>
+		struct remove_const<T const>
+		{
+			using type = T;
+		};
+	} // namespace detail
+
+	/// Implementation of a container similar to std::span in C++20.
+	template<typename T, u32 Length = detail::span_dynamic_length>
+	class span
+	{
+		template<typename U, u32 OtherLength>
+		friend class span;
+
+		T* data_{ nullptr };
+		u32 length_{ 0 };
+
+	public:
+		using iterator = T*;
+
+		explicit span()
+		{
+			static_assert(Length == 0 || Length == detail::span_dynamic_length);
+		}
+
+		explicit span(T* data, u32 const length)
+			: span{ data, length, {} }
+		{
+			static_assert(Length == detail::span_dynamic_length);
+		}
+
+		template<u32 ActualLength>
+		span(T (&data)[ActualLength])
+			: span{ data, ActualLength, {} }
+		{
+			static_assert(Length == ActualLength || Length == detail::span_dynamic_length);
+		}
+
+		span(span<typename detail::remove_const<T>::type, Length> const other)
+			: span{ other.data_, other.length_, {} }
+		{
+		}
+
+		auto get_data() const -> T* { return data_; }
+		auto get_length() const -> u32 { return length_; }
+
+		auto begin() const -> iterator { return data_; }
+		auto end() const -> iterator { return data_ + length_; }
+
+		auto subspan(u32 const first, u32 const length) const -> span<T> { return span{ data_ + first, length }; }
+		auto subspan(u32 const first) const -> span<T> { return subspan(length_ - first); }
+		template<u32 OtherLength>
+		auto subspan(u32 const first) const -> span<T, OtherLength> { return span<T, OtherLength>{ data_ + first, OtherLength, {} }; }
+
+		auto operator[](u32 const index) const -> T& { return data_[index]; }
+
+	private:
+		explicit span(T* data, u32 const length, detail::span_unchecked)
+			: data_{ data }
+			, length_{ length }
+		{
+		}
+	};
+} // namespace nes
\ No newline at end of file
diff --git a/lib/nes/common/string-builder.cc b/lib/nes/common/string-builder.cc
index efc1326..087f0d4 100644
--- a/lib/nes/common/string-builder.cc
+++ b/lib/nes/common/string-builder.cc
@@ -2,22 +2,21 @@
 
 namespace nes
 {
-	string_builder::string_builder(char* buffer, u32 buffer_length)
+	string_builder::string_builder(span<char> const buffer)
 		: buffer_{ buffer }
-		, buffer_length_{ buffer_length }
 	{
 	}
 
 	auto string_builder::append_char(char const value) -> string_builder&
 	{
-		if (actual_length_ == buffer_length_)
+		if (length_ == buffer_.get_length())
 		{
 			is_good_ = false;
 			return *this;
 		}
 
-		buffer_[actual_length_] = value;
-		actual_length_ += 1;
+		buffer_[length_] = value;
+		length_ += 1;
 		return *this;
 	}
 
diff --git a/lib/nes/common/string-builder.hh b/lib/nes/common/string-builder.hh
index e0bc673..256c267 100644
--- a/lib/nes/common/string-builder.hh
+++ b/lib/nes/common/string-builder.hh
@@ -1,6 +1,7 @@
 #pragma once
 
 #include "nes/common/types.hh"
+#include "nes/common/span.hh"
 #include <string_view>
 
 namespace nes
@@ -16,9 +17,8 @@ namespace nes
 	/// Builds a string into a fixed-length buffer.
 	class string_builder
 	{
-		char* buffer_{ nullptr };
-		u32 buffer_length_{ 0 };
-		u32 actual_length_{ 0 };
+		span<char> buffer_;
+		u32 length_{ 0 };
 		bool is_good_{ true };
 
 		enum class format_arg_type
@@ -60,10 +60,10 @@ namespace nes
 		};
 
 	public:
-		explicit string_builder(char* buffer, u32 buffer_length);
+		explicit string_builder(span<char>);
 
 		/// Get the resulting string.
-		auto get_result() const -> std::string_view { return std::string_view{ buffer_, actual_length_ }; }
+		auto get_result() const -> std::string_view { return std::string_view{ buffer_.get_data(), length_ }; }
 
 		/// Returns false after an invalid format string or buffer overflow.
 		auto is_good() const -> bool { return is_good_; }
@@ -104,7 +104,7 @@ namespace nes
 
 	public:
 		explicit string_buffer()
-			: string_builder{ buffer_, Capacity }
+			: string_builder{ buffer_ }
 		{
 		}
 	};