From 61c28f0e3dc37d15579504cd9b6552d15dbab368 Mon Sep 17 00:00:00 2001
From: Matthieu Gautier <mgautier@kymeria.fr>
Date: Thu, 8 Aug 2019 12:09:52 +0200
Subject: [PATCH] Make the regexTool thread safe.

---
 include/tools/regexTools.h |  3 --
 src/tools/regexTools.cpp   | 62 ++++++++++++++++++++------------------
 2 files changed, 32 insertions(+), 33 deletions(-)

diff --git a/include/tools/regexTools.h b/include/tools/regexTools.h
index cff6aaf98..f5656eedd 100644
--- a/include/tools/regexTools.h
+++ b/include/tools/regexTools.h
@@ -20,9 +20,6 @@
 #ifndef KIWIX_REGEXTOOLS_H
 #define KIWIX_REGEXTOOLS_H
 
-#include <unicode/regex.h>
-#include <unicode/ucnv.h>
-#include <map>
 #include <string>
 
 bool matchRegex(const std::string& content, const std::string& regex);
diff --git a/src/tools/regexTools.cpp b/src/tools/regexTools.cpp
index 912be6cd4..c31ffd525 100644
--- a/src/tools/regexTools.cpp
+++ b/src/tools/regexTools.cpp
@@ -18,40 +18,45 @@
  */
 
 #include <tools/regexTools.h>
+#include <tools/lock.h>
 
-std::map<std::string, icu::RegexMatcher*> regexCache;
+#include <unicode/regex.h>
+#include <unicode/ucnv.h>
 
-icu::RegexMatcher* buildRegex(const std::string& regex)
+#include <memory>
+#include <map>
+#include <pthread.h>
+
+std::map<std::string, std::shared_ptr<icu::RegexPattern>> regexCache;
+static pthread_mutex_t regexLock = PTHREAD_MUTEX_INITIALIZER;
+
+std::unique_ptr<icu::RegexMatcher> buildMatcher(const std::string& regex, const icu::UnicodeString& content)
 {
-  icu::RegexMatcher* matcher;
-  auto itr = regexCache.find(regex);
-
+  std::shared_ptr<icu::RegexPattern> pattern;
   /* Regex is in cache */
-  if (itr != regexCache.end()) {
-    matcher = itr->second;
+  try {
+    pattern = regexCache.at(regex);
+  } catch (std::out_of_range&) {
+    // Redo the search with a lock to avoid race condition.
+    kiwix::Lock l(&regexLock);
+    try {
+      pattern = regexCache.at(regex);
+    } catch (std::out_of_range&) {
+      UErrorCode status = U_ZERO_ERROR;
+      UParseError pe;
+      icu::UnicodeString uregex(regex.c_str());
+      pattern.reset(icu::RegexPattern::compile(uregex, UREGEX_CASE_INSENSITIVE, pe, status));
+      regexCache[regex] = pattern;
+    }
   }
-
-  /* Regex needs to be parsed (and cached) */
-  else {
-    UErrorCode status = U_ZERO_ERROR;
-    icu::UnicodeString uregex(regex.c_str());
-    matcher = new icu::RegexMatcher(uregex, UREGEX_CASE_INSENSITIVE, status);
-    regexCache[regex] = matcher;
-  }
-
-  return matcher;
+  UErrorCode status = U_ZERO_ERROR;
+  return std::unique_ptr<icu::RegexMatcher>(pattern->matcher(content, status));
 }
 
-/* todo */
-void freeRegexCache()
-{
-}
 bool matchRegex(const std::string& content, const std::string& regex)
 {
   ucnv_setDefaultName("UTF-8");
-  icu::UnicodeString ucontent(content.c_str());
-  auto matcher = buildRegex(regex);
-  matcher->reset(ucontent);
+  auto matcher = buildMatcher(regex, content.c_str());
   return matcher->find();
 }
 
@@ -60,10 +65,9 @@ std::string replaceRegex(const std::string& content,
                          const std::string& regex)
 {
   ucnv_setDefaultName("UTF-8");
-  icu::UnicodeString ucontent(content.c_str());
   icu::UnicodeString ureplacement(replacement.c_str());
-  auto matcher = buildRegex(regex);
-  matcher->reset(ucontent);
+  icu::UnicodeString ucontent(content.c_str());
+  auto matcher = buildMatcher(regex, ucontent);
   UErrorCode status = U_ZERO_ERROR;
   auto uresult = matcher->replaceAll(ureplacement, status);
   std::string tmp;
@@ -78,9 +82,7 @@ std::string appendToFirstOccurence(const std::string& content,
   ucnv_setDefaultName("UTF-8");
   icu::UnicodeString ucontent(content.c_str());
   icu::UnicodeString ureplacement(replacement.c_str());
-  auto matcher = buildRegex(regex);
-  matcher->reset(ucontent);
-
+  auto matcher = buildMatcher(regex, ucontent);
   if (matcher->find()) {
     UErrorCode status = U_ZERO_ERROR;
     ucontent.insert(matcher->end(status), ureplacement);