From 676cb37d0ee8a392984e3a0ad399380f44d804de Mon Sep 17 00:00:00 2001
From: MistEO <mistereo@hotmail.com>
Date: Fri, 24 May 2024 15:50:27 +0800
Subject: [PATCH] =?UTF-8?q?perf:=20=E8=A7=A3=E8=80=A6unicode=5Fescape?=
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---
 include/parser/parser.hpp | 183 +++++++++++++++++++++-----------------
 1 file changed, 101 insertions(+), 82 deletions(-)

diff --git a/include/parser/parser.hpp b/include/parser/parser.hpp
index 5556e2d..e6eac2e 100644
--- a/include/parser/parser.hpp
+++ b/include/parser/parser.hpp
@@ -57,6 +57,7 @@ class parser
     bool skip_string_literal_with_accel();
     bool skip_whitespace() noexcept;
     bool skip_digit();
+    bool skip_unicode_escape(uint16_t& pair_high, string_t& result);
 
 private:
     parsing_iter_t _cur;
@@ -443,90 +444,11 @@ inline std::optional<string_t> parser<string_t, parsing_t, accel_traits>::parse_
             case 't':
                 result.push_back('\t');
                 break;
-            case 'u': {
-                uint16_t cp = 0;
-                for (int i = 0; i < 4; i++) {
-                    ++_cur;
-                    if (_cur == _end) {
-                        return std::nullopt;
-                    }
-                    if (!std::isxdigit(static_cast<unsigned char>(*_cur))) {
-                        return std::nullopt;
-                    }
-                    cp <<= 4;
-                    if ('0' <= *_cur && *_cur <= '9') {
-                        cp |= *_cur - '0';
-                    }
-                    else if ('a' <= *_cur && *_cur <= 'f') {
-                        cp |= *_cur - 'a' + 10;
-                    }
-                    else if ('A' <= *_cur && *_cur <= 'F') {
-                        cp |= *_cur - 'A' + 10;
-                    }
-                    else {
-                        return std::nullopt;
-                    }
-                }
-                uint32_t ext_cp = cp;
-                uint16_t hi_cp = 0, lo_cp = 0;
-                if (0xD800 <= cp && cp <= 0xDBFF) {
-                    if (pair_high) {
-                        return std::nullopt;
-                    } else {
-                        pair_high = cp;
-                        break;
-                    }
-                } else if (0xDC00 <= cp && cp <= 0xDFFF) {
-                    if (!pair_high) {
-                        return std::nullopt;
-                    } else {
-                        ext_cp = (((pair_high - 0xD800) << 10) | (cp - 0xDC00)) + 0x10000;
-                        hi_cp = pair_high;
-                        lo_cp = cp;
-                        pair_high = 0;
-                    }
-                }
-                if constexpr (std::is_same_v<typename string_t::value_type, char>) {
-                    // utf8
-                    if (ext_cp <= 0x7F) {
-                        result.push_back(static_cast<char>(ext_cp));
-                    }
-                    else if (ext_cp <= 0x7FF) {
-                        result.push_back(static_cast<char>(((ext_cp >> 6) & 0b00011111) | 0b11000000u));
-                        result.push_back(static_cast<char>((ext_cp & 0b00111111) | 0b10000000u));
-                    }
-                    else if (ext_cp <= 0xFFFF) {
-                        result.push_back(
-                            static_cast<char>(((ext_cp >> 12) & 0b00001111) | 0b11100000u));
-                        result.push_back(static_cast<char>(((ext_cp >> 6) & 0b00111111) | 0b10000000u));
-                        result.push_back(static_cast<char>((ext_cp & 0b00111111) | 0b10000000u));
-                    } else {
-                        result.push_back(
-                            static_cast<char>(((ext_cp >> 18) & 0b00000111) | 0b11110000u));
-                        result.push_back(static_cast<char>(((ext_cp >> 12) & 0b00111111) | 0b10000000u));
-                        result.push_back(static_cast<char>(((ext_cp >> 6) & 0b00111111) | 0b10000000u));
-                        result.push_back(static_cast<char>((ext_cp & 0b00111111) | 0b10000000u));
-                    }
-                }
-                else if constexpr (std::is_same_v<typename string_t::value_type, wchar_t>) {
-                    if constexpr (sizeof (wchar_t) == 4) {
-                        result.push_back(static_cast<wchar_t>(ext_cp));
-                    } else if constexpr (sizeof (wchar_t) == 2) {
-                        if (ext_cp <= 0xFFFF) {
-                            result.push_back(static_cast<wchar_t>(ext_cp));
-                        } else {
-                            result.push_back(static_cast<wchar_t>(hi_cp));
-                            result.push_back(static_cast<wchar_t>(lo_cp));
-                        }
-                    } else {
-                        static_assert(!sizeof(typename string_t::value_type), "Unsupported wchar");
-                    }
-                }
-                else {
-                    static_assert(!sizeof(typename string_t::value_type), "Unsupported type");
+            case 'u':
+                if (!skip_unicode_escape(pair_high, result)) {
+                    return std::nullopt;
                 }
                 break;
-            }
             default:
                 // Illegal backslash escape
                 return std::nullopt;
@@ -552,6 +474,103 @@ inline std::optional<string_t> parser<string_t, parsing_t, accel_traits>::parse_
     return std::nullopt;
 }
 
+template <typename string_t, typename parsing_t, typename accel_traits>
+inline bool parser<string_t, parsing_t, accel_traits>::skip_unicode_escape(
+    uint16_t& pair_high,
+    string_t& result)
+{
+    uint16_t cp = 0;
+    for (int i = 0; i < 4; ++i) {
+        if (++_cur == _end) {
+            return false;
+        }
+
+        if (!std::isxdigit(static_cast<unsigned char>(*_cur))) {
+            return false;
+        }
+
+        cp <<= 4;
+
+        if ('0' <= *_cur && *_cur <= '9') {
+            cp |= *_cur - '0';
+        }
+        else if ('a' <= *_cur && *_cur <= 'f') {
+            cp |= *_cur - 'a' + 10;
+        }
+        else if ('A' <= *_cur && *_cur <= 'F') {
+            cp |= *_cur - 'A' + 10;
+        }
+        else {
+            return false;
+        }
+    }
+
+    uint32_t ext_cp = cp;
+    uint16_t hi_cp = 0, lo_cp = 0;
+
+    if (0xD800 <= cp && cp <= 0xDBFF) {
+        if (pair_high) {
+            return false;
+        }
+        pair_high = cp;
+        return true;
+    }
+
+    if (0xDC00 <= cp && cp <= 0xDFFF) {
+        if (!pair_high) {
+            return false;
+        }
+        ext_cp = (((pair_high - 0xD800) << 10) | (cp - 0xDC00)) + 0x10000;
+        hi_cp = pair_high;
+        lo_cp = cp;
+        pair_high = 0;
+    }
+
+    if constexpr (std::is_same_v<typename string_t::value_type, char>) {
+        // utf8
+        if (ext_cp <= 0x7F) {
+            result.push_back(static_cast<char>(ext_cp));
+        }
+        else if (ext_cp <= 0x7FF) {
+            result.push_back(static_cast<char>(((ext_cp >> 6) & 0b00011111) | 0b11000000u));
+            result.push_back(static_cast<char>((ext_cp & 0b00111111) | 0b10000000u));
+        }
+        else if (ext_cp <= 0xFFFF) {
+            result.push_back(static_cast<char>(((ext_cp >> 12) & 0b00001111) | 0b11100000u));
+            result.push_back(static_cast<char>(((ext_cp >> 6) & 0b00111111) | 0b10000000u));
+            result.push_back(static_cast<char>((ext_cp & 0b00111111) | 0b10000000u));
+        }
+        else {
+            result.push_back(static_cast<char>(((ext_cp >> 18) & 0b00000111) | 0b11110000u));
+            result.push_back(static_cast<char>(((ext_cp >> 12) & 0b00111111) | 0b10000000u));
+            result.push_back(static_cast<char>(((ext_cp >> 6) & 0b00111111) | 0b10000000u));
+            result.push_back(static_cast<char>((ext_cp & 0b00111111) | 0b10000000u));
+        }
+    }
+    else if constexpr (std::is_same_v<typename string_t::value_type, wchar_t>) {
+        if constexpr (sizeof(wchar_t) == 4) {
+            result.push_back(static_cast<wchar_t>(ext_cp));
+        }
+        else if constexpr (sizeof(wchar_t) == 2) {
+            if (ext_cp <= 0xFFFF) {
+                result.push_back(static_cast<wchar_t>(ext_cp));
+            }
+            else {
+                result.push_back(static_cast<wchar_t>(hi_cp));
+                result.push_back(static_cast<wchar_t>(lo_cp));
+            }
+        }
+        else {
+            static_assert(!sizeof(typename string_t::value_type), "Unsupported wchar");
+        }
+    }
+    else {
+        static_assert(!sizeof(typename string_t::value_type), "Unsupported type");
+    }
+
+    return true;
+}
+
 template <typename string_t, typename parsing_t, typename accel_traits>
 inline bool parser<string_t, parsing_t, accel_traits>::skip_string_literal_with_accel()
 {