From 813ea3055d8b79be62024ad617d08e0662206c8b Mon Sep 17 00:00:00 2001
From: dragonmux <git@dragonmux.network>
Date: Wed, 1 Nov 2023 00:38:39 +0000
Subject: [PATCH] console: Implemented Linux and macOS support for displaying
 UTF-16 strings

---
 impl/console.cxx  | 59 ++++++++++++++++++++++++++++++++++++++++++++++-
 substrate/console |  5 +++-
 2 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/impl/console.cxx b/impl/console.cxx
index 9d7e26b6..65a123fd 100644
--- a/impl/console.cxx
+++ b/impl/console.cxx
@@ -124,7 +124,7 @@ namespace substrate
 			write(static_cast<const void *>(value), sizeof(char16_t) * valueLen);
 			_setmode(fd, consoleMode);
 #else
-			//
+			convertingWrite(value, valueLen);
 #endif
 		}
 		else
@@ -209,5 +209,62 @@ namespace substrate
 			defaults(outputStream);
 		outputStream.write(' ');
 	}
+
+	// Performs safe indexing into the string array, returning the invalid value 0xffff if outside the bounds of the array
+	static inline uint16_t safeIndex(const char16_t *const string, const size_t length, const size_t index) noexcept
+	{
+		if (index >= length)
+			return UINT16_MAX;
+		uint16_t result{};
+		// NOLINTNEXTLINE(cppcoreguidelines-pro-bounds-pointer-arithmetic)
+		memcpy(&result, string + index, sizeof(char16_t));
+		return result;
+	}
+
+	// These functions implement streamed UTF-16 to UTF-8 conversion for display
+#ifndef _WIN32
+	// Convert and stream out the converted code points given by string to the fd
+	void consoleStream_t::convertingWrite(const char16_t *string, const size_t stringLen) const noexcept
+	{
+		for (size_t offset = 0; offset < stringLen; ++offset)
+		{
+			const auto unitA{safeIndex(string, stringLen, offset)};
+			// Check if this is a high-half surrogate pair
+			if ((unitA & 0xfe00U) == 0xd800U)
+			{
+				// Recover the upper 10 (11) bits from the first surrogate of the pair.
+				const auto upper{(unitA & 0x03ffU) + 0x0040U};
+				// Recover the lower 10 bits from the second surrogate of the pair.
+				const auto lower{safeIndex(string, stringLen, ++offset) & 0x03fffU};
+
+				// Encode the 4 code units and write them out
+				write(static_cast<char>(0xf0U | (uint8_t(upper >> 8U) & 0x07U)));
+				write(static_cast<char>(0x80U | (uint8_t(upper >> 2U) & 0x3fU)));
+				write(static_cast<char>(0x80U | (uint8_t(upper << 4U) & 0x30U) | (uint8_t(lower >> 6U) & 0x0fU)));
+				write(static_cast<char>(0x80U | (lower & 0x3fU)));
+			}
+			else
+			{
+				// Something from the Basic Multilingual Plane, figure out how to encode it.
+				// If it's able to be represented as a single byte, write it out as one
+				if (unitA <= 0x007fU)
+					write(static_cast<char>(unitA));
+				// If it's two byte, encode and write out as a code unit pair
+				else if (unitA <= 0x07ffU)
+				{
+					write(static_cast<char>(0xc0U | (uint8_t(unitA >> 6U) & 0x1fU)));
+					write(static_cast<char>(0x80U | uint8_t(unitA & 0x3fU)));
+				}
+				// Otherwise it's 3 byte, encode and write out as a code unit tripple
+				else
+				{
+					write(static_cast<char>(0xe0U | (uint8_t(unitA >> 12U) & 0x0fU)));
+					write(static_cast<char>(0x80U | (uint8_t(unitA >> 6U) & 0x3fU)));
+					write(static_cast<char>(0x80U | (unitA & 0x3fU)));
+				}
+			}
+		}
+	}
+#endif
 } // namespace substrate
 /* vim: set ft=cpp ts=4 sw=4 noexpandtab: */
diff --git a/substrate/console b/substrate/console
index dc8707ec..ccc150c1 100644
--- a/substrate/console
+++ b/substrate/console
@@ -53,13 +53,16 @@ namespace substrate
 		bool _tty{false};
 
 		void checkTTY() noexcept;
+#ifndef _WIN32
+		void convertingWrite(const char16_t *string, const size_t stringLen) const noexcept;
+#endif
 
 	public:
 		constexpr consoleStream_t() noexcept = default;
 		consoleStream_t(const int32_t desc) noexcept : fd{desc} { checkTTY(); }
 		SUBSTRATE_NO_DISCARD(constexpr bool valid() const noexcept) { return fd != -1; }
 		SUBSTRATE_NO_DISCARD(constexpr bool isTTY() const noexcept) { return _tty; }
-#if defined(_WIN32)
+#ifdef _WIN32
 		SUBSTRATE_NO_DISCARD(void *handle() const noexcept)
 			{ return reinterpret_cast<void *>(_get_osfhandle(fd)); }
 #endif