regex_remap: convert from pcre to Regex (#12575)

* regex_remap: convert from pcre to Regex

* get RegexMatchContext helper class working

* cleanup

* remove pcre2 match context features not in centos

* add back in comments from the pcre plugin

* refactor Regex::captureCount(), add unit tests

* change Regex api function convention, add to unit test

* better handling of regex exec call failure

* use errmsg in diags.log, restore older match limit test

Author: traeak

include/tsutil/Regex.h

@@ -94,6 +94,41 @@ class RegexMatches
   _MatchDataPtr _match_data;
 };
 
+/// @brief Wrapper for PCRE2 match context
+///
+/// @internal This instance is not tied to any Regex and can be used with one of the Regex::exec overloads.
+class RegexMatchContext
+{
+  friend class Regex;
+
+public:
+  /** Construct a new RegexMatchContext object.
+   */
+  RegexMatchContext();
+  ~RegexMatchContext();
+
+  /// uses pcre2_match_context_copy for a deep copy.
+  RegexMatchContext(RegexMatchContext const &orig);
+  RegexMatchContext &operator=(RegexMatchContext const &orig);
+
+  RegexMatchContext(RegexMatchContext &&)            = default;
+  RegexMatchContext &operator=(RegexMatchContext &&) = default;
+
+  /** Limits the amount of backtracking that can take place.
+   * Any regex exec call that fails will return PCRE2_ERROR_MATCHLIMIT(-47)
+   */
+  void set_match_limit(uint32_t limit);
+
+private:
+  /// @internal This wraps a void* so to avoid requiring a pcre2 include.
+  struct _MatchContext;
+  struct _MatchContextPtr {
+    void *_ptr = nullptr;
+  };
+
+  _MatchContextPtr _match_context;
+};
+
 /// @brief Wrapper for PCRE2 regular expression.
 class Regex
 {
@@ -179,17 +214,28 @@ class Regex
    * @param subject String to match against.
    * @param matches Place to store the capture groups.
    * @param flags Match flags (e.g., RE_NOTEMPTY).
+   * @param optional context Match context (set matching limits).
    * @return @c The number of capture groups. < 0 if an error occurred. 0 if the number of Matches is too small.
    *
    * It is safe to call this method concurrently on the same instance of @a this.
    *
    * Each capture group takes 3 elements of @a ovector, therefore @a ovecsize must
    * be a multiple of 3 and at least three times the number of desired capture groups.
    */
-  int exec(std::string_view subject, RegexMatches &matches, uint32_t flags) const;
+  int exec(std::string_view subject, RegexMatches &matches, uint32_t flags,
+           RegexMatchContext const *const matchContext = nullptr) const;
+
+  /** Error string for exec failure.
+   *
+   * @param int return code from exec call.
+   */
+  static std::string get_error_string(int rc);
+
+  /// @return The number of capture groups in the compiled pattern, -1 for fail.
+  int32_t get_capture_count() const;
 
-  /// @return The number of capture groups in the compiled pattern.
-  int get_capture_count();
+  /// @return number of highest back references, -1 for fail.
+  int32_t get_backref_max() const;
 
   /// @return Is the compiled pattern empty?
   bool empty() const;

plugins/experimental/cookie_remap/cookie_remap.cc

@@ -445,7 +445,7 @@ class subop
 
   Regex      *regex = nullptr;
   std::string regex_string;
-  int         regex_ccount = 0;
+  int32_t     regex_ccount = 0;
 
   std::string  bucket;
   unsigned int how_many = 0;

plugins/regex_remap/CMakeLists.txt

@@ -17,6 +17,6 @@
 
 add_atsplugin(regex_remap regex_remap.cc)
 
-target_link_libraries(regex_remap PRIVATE PCRE::PCRE libswoc::libswoc)
+target_link_libraries(regex_remap PRIVATE libswoc::libswoc)
 
 verify_remap_plugin(regex_remap)