build(antlr): 引入第三方 ANTLR4 runtime/tool 并接入构建

third_party/antlr4-runtime-4.13.2/runtime/src/support/Utf8.h

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+/* Copyright (c) 2021 The ANTLR Project. All rights reserved.
+ * Use of this file is governed by the BSD 3-clause license that
+ * can be found in the LICENSE.txt file in the project root.
+ */
+
+#pragma once
+
+#include <optional>
+#include <string>
+#include <string_view>
+#include <tuple>
+
+#include "antlr4-common.h"
+
+namespace antlrcpp {
+
+  class ANTLR4CPP_PUBLIC Utf8 final {
+  public:
+    // Decodes the next code point, returning the decoded code point and the number
+    // of code units (a.k.a. bytes) consumed. In the event that an invalid code unit
+    // sequence is returned the replacement character, U+FFFD, is returned with a
+    // code unit count of 1. As U+FFFD requires 3 code units when encoded, this can
+    // be used to differentiate valid input from malformed input.
+    static std::pair<char32_t, size_t> decode(std::string_view input);
+
+    // Decodes the given UTF-8 encoded input into a string of code points.
+    static std::optional<std::u32string> strictDecode(std::string_view input);
+
+    // Decodes the given UTF-8 encoded input into a string of code points. Unlike strictDecode(),
+    // each byte in an illegal byte sequence is replaced with the Unicode replacement character,
+    // U+FFFD.
+    static std::u32string lenientDecode(std::string_view input);
+
+    // Encodes the given code point and appends it to the buffer. If the code point
+    // is an unpaired surrogate or outside of the valid Unicode range it is replaced
+    // with the replacement character, U+FFFD.
+    static std::string& encode(std::string *buffer, char32_t codePoint);
+
+    // Encodes the given Unicode code point string as UTF-8.
+    static std::optional<std::string> strictEncode(std::u32string_view input);
+
+    // Encodes the given Unicode code point string as UTF-8. Unlike strictEncode(),
+    // each invalid Unicode code point is replaced with the Unicode replacement character, U+FFFD.
+    static std::string lenientEncode(std::u32string_view input);
+
+  private:
+    Utf8() = delete;
+    Utf8(const Utf8&) = delete;
+    Utf8(Utf8&&) = delete;
+    Utf8& operator=(const Utf8&) = delete;
+    Utf8& operator=(Utf8&&) = delete;
+  };
+
+}