From 4ff796a59063f2de4fd8e28405244b3abb15a837 Mon Sep 17 00:00:00 2001
From: tastytea <tastytea@tastytea.de>
Date: Fri, 28 May 2021 19:07:27 +0200
Subject: [PATCH] Make regular expressions static variables.
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Fewer allocations → faster program. About 17% speed increase with 89 books on up
to 3 cores. Measured using the average of 4 runs.
Before: ~15,5 seconds
 After: ~12,8 seconds

Calls to allocation functions went down from 16.652.583 to 5.059.301.
---
 src/search.cpp | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/src/search.cpp b/src/search.cpp
index 7cd5891..050bfbc 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -31,8 +31,8 @@ namespace epubgrep::search
 
 using std::string;
 
-std::vector<match> search(const fs::path &filepath, std::string_view regex,
-                          const settings &opts)
+std::vector<match> search(const fs::path &filepath,
+                          const std::string_view regex, const settings &opts)
 {
     boost::regex::flag_type flags{};
 
@@ -107,17 +107,21 @@ std::vector<match> search(const fs::path &filepath, std::string_view regex,
 
 void cleanup_text(string &text)
 {
+    static const boost::regex re_header_start{"<[hH][1-6]"};
+    static const boost::regex re_header_end{"</[hH]"};
+    static const boost::regex re_pagebreak{".+pagebreak.+(title|aria-label)"
+                                           "=\"([[:alnum:]]+)\".*"};
+
     size_t pos{};
     while ((pos = text.find('<', pos)) != string::npos)
     {
         // Mark headlines. We need them later on.
         string replacement;
-        if (boost::regex_match(text.substr(pos, 3), boost::regex{"<[hH][1-6]"}))
+        if (boost::regex_match(text.substr(pos, 3), re_header_start))
         {
             replacement = "<H>";
         }
-        else if (boost::regex_match(text.substr(pos, 3),
-                                    boost::regex{"</[hH]"}))
+        else if (boost::regex_match(text.substr(pos, 3), re_header_end))
         {
             replacement = "</H>";
         }
@@ -125,8 +129,6 @@ void cleanup_text(string &text)
         {
             auto endpos{text.find('>')};
             boost::match_results<const char *> match;
-            const boost::regex re_pagebreak{".+pagebreak.+(title|aria-label)"
-                                            "=\"([[:alnum:]]+)\".*"};
             if (boost::regex_search(text.substr(pos, endpos).data(), match,
                                     re_pagebreak))
             {