AK: Add UnicodeUtils with Unicode-related helper functions

This introduces the UnicodeUtils file, which contains helper functions
related to Unicode. This is in contrast to StringUtils, whose functions
are not directly related to Unicode and are, in theory,
encoding-agnostic.

AK/UnicodeUtils.cpp

@@ -0,0 +1,37 @@
+/*
+ * Copyright (c) 2021, Max Wipfli <mail@maxwipfli.ch>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Array.h>
+#include <AK/Optional.h>
+#include <AK/StringView.h>
+#include <AK/UnicodeUtils.h>
+
+namespace AK::UnicodeUtils {
+
+Optional<StringView> get_unicode_control_code_point_alias(u32 code_point)
+{
+    static constexpr Array<StringView, 32> ascii_controls_lookup_table = {
+        "NUL", "SOH", "STX", "ETX", "EOT", "ENQ", "ACK", "BEL",
+        "BS", "HT", "LF", "VT", "FF", "CR", "SO", "SI",
+        "DLE", "DC1", "DC2", "DC3", "DC4", "NAK", "SYN", "ETB",
+        "CAN", "EM", "SUB", "ESC", "FS", "GS", "RS", "US"
+    };
+
+    static constexpr Array<StringView, 32> c1_controls_lookup_table = {
+        "XXX", "XXX", "BPH", "NBH", "IND", "NEL", "SSA", "ESA",
+        "HTS", "HTJ", "VTS", "PLD", "PLU", "RI", "SS2", "SS3",
+        "DCS", "PU1", "PU2", "STS", "CCH", "MW", "SPA", "EPA",
+        "SOS", "XXX", "SCI", "CSI", "ST", "OSC", "PM", "APC"
+    };
+
+    if (code_point < 0x20)
+        return ascii_controls_lookup_table[code_point];
+    if (code_point >= 0x80 && code_point < 0xa0)
+        return c1_controls_lookup_table[code_point - 0x80];
+    return {};
+}
+
+}

AK/UnicodeUtils.h

@@ -0,0 +1,20 @@
+/*
+ * Copyright (c) 2021, Max Wipfli <mail@maxwipfli.ch>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <AK/Forward.h>
+
+namespace AK::UnicodeUtils {
+
+constexpr bool is_unicode_control_code_point(u32 code_point)
+{
+    return code_point < 0x20 || (code_point >= 0x80 && code_point < 0xa0);
+}
+
+Optional<StringView> get_unicode_control_code_point_alias(u32);
+
+}