LibC: Start work on locales

This patch adds 2 locales, POSIX locale and UTF8 locale.

functions `mbstowcs()` and `strcoll()` use locales to do convertions and
comparison respectively.

userspace/libraries/LibC/locale.cpp

@@ -1,15 +1,112 @@
+#include <BAN/Assert.h>
+
 #include <locale.h>
+#include <stdio.h>
 #include <string.h>
 
-// FIXME: Actually support locales
-char* setlocale(int category, const char* locale)
-{
-	(void)category;
+static locale_t s_current_locales[LC_ALL] {
+	LOCALE_POSIX,
+	LOCALE_POSIX,
+	LOCALE_POSIX,
+	LOCALE_POSIX,
+	LOCALE_POSIX,
+	LOCALE_POSIX,
+};
+static_assert(LC_ALL == 6);
 
-	static char s_locale[] = "C";
-	if (locale == nullptr)
-		return s_locale;
-	if (strcmp(locale, "") == 0 || strcmp(locale, "C") == 0 || strcmp(locale, "POSIX") == 0)
-		return s_locale;
-	return nullptr;
+static locale_t str_to_locale(const char* locale)
+{
+	if (*locale == '\0')
+		return LOCALE_UTF8;
+
+	if (strcmp(locale, "C") == 0 || strcmp(locale, "LOCALE_POSIX") == 0)
+		return LOCALE_POSIX;
+	if (strcmp(locale, "C.UTF8") == 0)
+		return LOCALE_UTF8;
+	return LOCALE_INVALID;
+}
+
+static const char* locale_to_str(locale_t locale)
+{
+	if (locale == LOCALE_POSIX)
+		return "C";
+	if (locale == LOCALE_UTF8)
+		return "C.UTF8";
+	ASSERT_NOT_REACHED();
+}
+
+char* setlocale(int category, const char* locale_str)
+{
+	static char s_locale_buffer[128];
+
+	if (locale_str == nullptr)
+	{
+		switch (category)
+		{
+			case LC_COLLATE:
+			case LC_CTYPE:
+			case LC_MESSAGES:
+			case LC_MONETARY:
+			case LC_NUMERIC:
+			case LC_TIME:
+				strcpy(s_locale_buffer, locale_to_str(s_current_locales[category]));
+				break;
+			case LC_ALL:
+				sprintf(s_locale_buffer, "%s;%s;%s;%s;%s;%s",
+					locale_to_str(s_current_locales[0]),
+					locale_to_str(s_current_locales[1]),
+					locale_to_str(s_current_locales[2]),
+					locale_to_str(s_current_locales[3]),
+					locale_to_str(s_current_locales[4]),
+					locale_to_str(s_current_locales[5])
+				);
+				break;
+			default:
+				return nullptr;
+		}
+
+		return s_locale_buffer;
+	}
+
+	locale_t locale = str_to_locale(locale_str);
+	if (locale == LOCALE_INVALID)
+		return nullptr;
+
+	switch (category)
+	{
+		case LC_COLLATE:
+		case LC_CTYPE:
+		case LC_MESSAGES:
+		case LC_MONETARY:
+		case LC_NUMERIC:
+		case LC_TIME:
+			s_current_locales[category] = locale;
+			break;
+		case LC_ALL:
+			for (auto& current : s_current_locales)
+				current = locale;
+			break;
+		default:
+			return nullptr;
+	}
+
+	strcpy(s_locale_buffer, locale_to_str(locale));
+	return s_locale_buffer;
+}
+
+
+locale_t __getlocale(int category)
+{
+	switch (category)
+	{
+		case LC_COLLATE:
+		case LC_CTYPE:
+		case LC_MESSAGES:
+		case LC_MONETARY:
+		case LC_NUMERIC:
+		case LC_TIME:
+			return s_current_locales[category];
+		default:
+			return LOCALE_INVALID;
+	}
 }