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94 lines
3.1 KiB
C++
94 lines
3.1 KiB
C++
// This file is distributed under the BSD License.
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// See "license.txt" for details.
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// http://www.chaiscript.com
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#ifndef CHAISCRIPT_UTILITY_UNICODE_HPP_
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#define CHAISCRIPT_UTILITY_UNICODE_HPP_
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#include <cstddef>
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#include <cstdint>
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#include <string>
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namespace chaiscript {
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namespace utility {
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namespace unicode {
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inline constexpr std::uint32_t max_codepoint = 0x10FFFF;
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constexpr bool is_surrogate(std::uint32_t cp) noexcept {
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return cp >= 0xD800 && cp <= 0xDFFF;
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}
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// Append cp to out as UTF-8. Returns bytes written, or 0 if cp >= 0x200000.
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// Surrogates are not rejected here; callers that care check is_surrogate() first.
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inline std::size_t append_utf8(std::string &out, std::uint32_t cp) {
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if (cp < 0x80) {
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out += static_cast<char>(cp);
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return 1;
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}
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if (cp < 0x800) {
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out += static_cast<char>(0xC0 | (cp >> 6));
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out += static_cast<char>(0x80 | (cp & 0x3F));
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return 2;
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}
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if (cp < 0x10000) {
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out += static_cast<char>(0xE0 | (cp >> 12));
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out += static_cast<char>(0x80 | ((cp >> 6) & 0x3F));
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out += static_cast<char>(0x80 | (cp & 0x3F));
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return 3;
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}
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if (cp < 0x200000) {
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out += static_cast<char>(0xF0 | (cp >> 18));
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out += static_cast<char>(0x80 | ((cp >> 12) & 0x3F));
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out += static_cast<char>(0x80 | ((cp >> 6) & 0x3F));
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out += static_cast<char>(0x80 | (cp & 0x3F));
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return 4;
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}
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return 0;
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}
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// Append cp to out as UTF-16. Returns code units written, or 0 if cp is
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// a surrogate or > max_codepoint.
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template<typename CharT>
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inline std::size_t append_utf16(std::basic_string<CharT> &out, std::uint32_t cp) {
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if (is_surrogate(cp) || cp > max_codepoint) {
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return 0;
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}
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if (cp < 0x10000) {
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out += static_cast<CharT>(cp);
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return 1;
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}
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const std::uint32_t v = cp - 0x10000;
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out += static_cast<CharT>(0xD800 | (v >> 10));
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out += static_cast<CharT>(0xDC00 | (v & 0x3FF));
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return 2;
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}
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// Append cp to a basic_string<CharT>. Dispatches on sizeof(CharT):
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// 1 byte -> UTF-8, 2 bytes -> UTF-16, 4 bytes -> UTF-32.
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// Returns code units written, or 0 if the codepoint is invalid.
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template<typename CharT>
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inline std::size_t append_codepoint(std::basic_string<CharT> &out, std::uint32_t cp) {
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if constexpr (sizeof(CharT) == 1) {
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std::string tmp;
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const auto n = append_utf8(tmp, cp);
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out.append(tmp.begin(), tmp.end());
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return n;
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} else if constexpr (sizeof(CharT) == 2) {
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return append_utf16(out, cp);
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} else {
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static_assert(sizeof(CharT) == 4, "append_codepoint: unsupported CharT size");
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if (is_surrogate(cp) || cp > max_codepoint) {
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return 0;
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}
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out += static_cast<CharT>(cp);
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return 1;
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}
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}
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} // namespace unicode
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} // namespace utility
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} // namespace chaiscript
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#endif
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