From ca2b030336d9cd58f49248fca8cde04fefe9319a Mon Sep 17 00:00:00 2001
From: Timothy Flynn <trflynn89@pm.me>
Date: Sun, 5 Mar 2023 10:14:25 -0500
Subject: [PATCH] LibUnicode: Use binary search for lookups into the generated
 emoji data

This sorts the array of generated emoji data by code point (first by
code point length, then by code point value). This lets us use a binary
search to find emoji data, rather than the current linear search.

In a profile of scrolling around /home/anon/Documents/emoji.txt, this
reduces the runtime of Gfx::Emoji::emoji_for_code_points from 69.03% to
28.42%. Within that, Unicode::find_emoji_for_code_points reduces from
28.42% to just 1.95%.
---
 .../LibUnicode/GenerateEmojiData.cpp          | 71 +++++++++++++------
 1 file changed, 51 insertions(+), 20 deletions(-)

diff --git a/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp b/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp
index fa9ade687d..0474357668 100644
--- a/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/LibUnicode/GenerateEmojiData.cpp
@@ -7,6 +7,7 @@
 #include "GeneratorUtil.h"
 #include <AK/AnyOf.h>
 #include <AK/DeprecatedString.h>
+#include <AK/QuickSort.h>
 #include <AK/SourceGenerator.h>
 #include <AK/StringUtils.h>
 #include <AK/Types.h>
@@ -306,13 +307,27 @@ static constexpr Array<EmojiData, @emojis_size@> s_emojis { {)~~~");
     generator.append(R"~~~(
 } };
 
+struct EmojiCodePointComparator {
+    constexpr int operator()(ReadonlySpan<u32> code_points, EmojiData const& emoji)
+    {
+        auto emoji_code_points = emoji.code_points();
+
+        if (code_points.size() != emoji_code_points.size())
+            return static_cast<int>(code_points.size()) - static_cast<int>(emoji_code_points.size());
+
+        for (size_t i = 0; i < code_points.size(); ++i) {
+            if (code_points[i] != emoji_code_points[i])
+                return static_cast<int>(code_points[i]) - static_cast<int>(emoji_code_points[i]);
+        }
+
+        return 0;
+    }
+};
+
 Optional<Emoji> find_emoji_for_code_points(ReadonlySpan<u32> code_points)
 {
-    for (auto& emoji : s_emojis) {
-        if (emoji.code_points() == code_points)
-            return emoji.to_unicode_emoji();
-    }
-
+    if (auto const* emoji = binary_search(s_emojis, code_points, nullptr, EmojiCodePointComparator {}))
+        return emoji->to_unicode_emoji();
     return {};
 }
 
@@ -400,22 +415,8 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         TRY(validate_emoji(emoji_resource_path, emoji_data));
     }
 
-    size_t code_point_array_index { 0 };
-    for (auto& emoji : emoji_data.emojis) {
-        emoji.code_point_array_index = code_point_array_index;
-        code_point_array_index += emoji.code_points.size();
-
+    for (auto& emoji : emoji_data.emojis)
         set_image_path_for_emoji(emoji_resource_path, emoji_data, emoji);
-    }
-
-    if (!generated_header_path.is_empty()) {
-        auto generated_header_file = TRY(open_file(generated_header_path, Core::File::OpenMode::Write));
-        TRY(generate_emoji_data_header(*generated_header_file, emoji_data));
-    }
-    if (!generated_implementation_path.is_empty()) {
-        auto generated_implementation_file = TRY(open_file(generated_implementation_path, Core::File::OpenMode::Write));
-        TRY(generate_emoji_data_implementation(*generated_implementation_file, emoji_data));
-    }
 
     if (!generated_installation_path.is_empty()) {
         TRY(Core::Directory::create(LexicalPath { generated_installation_path }.parent(), Core::Directory::CreateDirectories::Yes));
@@ -424,5 +425,35 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
         TRY(generate_emoji_installation(*generated_installation_file, emoji_data));
     }
 
+    if (!generated_header_path.is_empty()) {
+        auto generated_header_file = TRY(open_file(generated_header_path, Core::File::OpenMode::Write));
+        TRY(generate_emoji_data_header(*generated_header_file, emoji_data));
+    }
+
+    if (!generated_implementation_path.is_empty()) {
+        quick_sort(emoji_data.emojis, [](auto const& lhs, auto const& rhs) {
+            if (lhs.code_points.size() != rhs.code_points.size())
+                return lhs.code_points.size() < rhs.code_points.size();
+
+            for (size_t i = 0; i < lhs.code_points.size(); ++i) {
+                if (lhs.code_points[i] < rhs.code_points[i])
+                    return true;
+                if (lhs.code_points[i] > rhs.code_points[i])
+                    return false;
+            }
+
+            return false;
+        });
+
+        size_t code_point_array_index { 0 };
+        for (auto& emoji : emoji_data.emojis) {
+            emoji.code_point_array_index = code_point_array_index;
+            code_point_array_index += emoji.code_points.size();
+        }
+
+        auto generated_implementation_file = TRY(open_file(generated_implementation_path, Core::File::OpenMode::Write));
+        TRY(generate_emoji_data_implementation(*generated_implementation_file, emoji_data));
+    }
+
     return 0;
 }