BAN: Implement GUID::to_string

BAN/include/BAN/GUID.h

@@ -1,7 +1,7 @@
 #pragma once
 
 #include <BAN/Optional.h>
-#include <BAN/StringView.h>
+#include <BAN/String.h>
 
 #include <string.h>
 
@@ -19,6 +19,54 @@ namespace BAN
 		{
 			return memcmp(this, &other, sizeof(GUID)) == 0;
 		}
+
+		BAN::ErrorOr<BAN::String> to_string() const
+		{
+			char buffer[37];
+			char* ptr = buffer;
+
+			const auto append_hex_nibble =
+				[&ptr](uint8_t nibble)
+				{
+					if (nibble < 10)
+						*ptr++ = '0' + nibble;
+					else
+						*ptr++ = 'A' + nibble - 10;
+				};
+
+			const auto append_hex_byte =
+				[&append_hex_nibble](uint8_t byte)
+				{
+					append_hex_nibble(byte >> 4);
+					append_hex_nibble(byte & 0xF);
+				};
+
+			append_hex_byte((component1 >> 24) & 0xFF);
+			append_hex_byte((component1 >> 16) & 0xFF);
+			append_hex_byte((component1 >>  8) & 0xFF);
+			append_hex_byte((component1 >>  0) & 0xFF);
+			*ptr++ = '-';
+			append_hex_byte((component2 >>  8) & 0xFF);
+			append_hex_byte((component2 >>  0) & 0xFF);
+			*ptr++ = '-';
+			append_hex_byte((component3 >>  8) & 0xFF);
+			append_hex_byte((component3 >>  0) & 0xFF);
+			*ptr++ = '-';
+			append_hex_byte(component45[0]);
+			append_hex_byte(component45[1]);
+			*ptr++ = '-';
+			append_hex_byte(component45[2]);
+			append_hex_byte(component45[3]);
+			append_hex_byte(component45[4]);
+			append_hex_byte(component45[5]);
+			append_hex_byte(component45[6]);
+			append_hex_byte(component45[7]);
+			*ptr = '\0';
+
+			BAN::String guid;
+			TRY(guid.append(buffer));
+			return BAN::move(guid);
+		}
 	};
 	static_assert(sizeof(GUID) == 16);