1 files changed, 707 insertions, 0 deletions
diff --git a/xpcom/string/RustRegex.h b/xpcom/string/RustRegex.h
new file mode 100644
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--- /dev/null
+++ b/xpcom/string/RustRegex.h
@@ -0,0 +1,707 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_RustRegex_h
+#define mozilla_RustRegex_h
+
+#include "nsPrintfCString.h"
+#include "nsTArray.h"
+#include "rure.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/UniquePtr.h"
+
+namespace mozilla {
+
+// This header is a thin wrapper around the `rure.h` header file, which declares
+// the C API for interacting with the rust `regex` crate. This is intended to
+// make the type more ergonomic to use with mozilla types.
+
+class RustRegex;
+class RustRegexSet;
+class RustRegexOptions;
+class RustRegexCaptures;
+class RustRegexIter;
+class RustRegexIterCaptureNames;
+
+using RustRegexMatch = rure_match;
+
+/*
+ * RustRegexCaptures represents storage for sub-capture locations of a match.
+ *
+ * Computing the capture groups of a match can carry a significant performance
+ * penalty, so their use in the API is optional.
+ *
+ * A RustRegexCaptures value may outlive its corresponding RustRegex and can be
+ * freed independently.
+ *
+ * It is not safe to use from multiple threads simultaneously.
+ */
+class RustRegexCaptures final {
+ public:
+  RustRegexCaptures() = default;
+
+  // Check if the `RustRegexCaptures` object is valid.
+  bool IsValid() const { return mPtr != nullptr; }
+  explicit operator bool() const { return IsValid(); }
+
+  /*
+   * CaptureAt returns Some if and only if the capturing group at the
+   * index given was part of the match. If so, the returned RustRegexMatch
+   * object contains the start and end offsets (in bytes) of the match.
+   *
+   * If no capture group with the index aIdx exists, or the group was not part
+   * of the match, then Nothing is returned.  (A capturing group exists if and
+   * only if aIdx is less than Length().)
+   *
+   * Note that index 0 corresponds to the full match.
+   */
+  Maybe<RustRegexMatch> CaptureAt(size_t aIdx) const {
+    RustRegexMatch match;
+    if (mPtr && rure_captures_at(mPtr.get(), aIdx, &match)) {
+      return Some(match);
+    }
+    return Nothing();
+  }
+  Maybe<RustRegexMatch> operator[](size_t aIdx) const {
+    return CaptureAt(aIdx);
+  }
+
+  /*
+   * Returns the number of capturing groups in this `RustRegexCaptures`.
+   */
+  size_t Length() const { return mPtr ? rure_captures_len(mPtr.get()) : 0; }
+
+ private:
+  friend class RustRegex;
+  friend class RustRegexIter;
+
+  explicit RustRegexCaptures(rure* aRe)
+      : mPtr(aRe ? rure_captures_new(aRe) : nullptr) {}
+
+  struct Deleter {
+    void operator()(rure_captures* ptr) const { rure_captures_free(ptr); }
+  };
+  UniquePtr<rure_captures, Deleter> mPtr;
+};
+
+/*
+ * RustRegexIterCaptureNames is an iterator over the list of capture group names
+ * in this particular RustRegex.
+ *
+ * A RustRegexIterCaptureNames value may not outlive its corresponding
+ * RustRegex, and should be destroyed before its corresponding RustRegex is
+ * destroyed.
+ *
+ * It is not safe to use from multiple threads simultaneously.
+ */
+class RustRegexIterCaptureNames {
+ public:
+  RustRegexIterCaptureNames() = delete;
+
+  // Check if the `RustRegexIterCaptureNames` object is valid.
+  bool IsValid() const { return mPtr != nullptr; }
+  explicit operator bool() const { return IsValid(); }
+
+  /*
+   * Advances the iterator and returns true if and only if another capture group
+   * name exists.
+   *
+   * The value of the capture group name is written to the provided pointer.
+   */
+  mozilla::Maybe<const char*> Next() {
+    char* next = nullptr;
+    if (mPtr && rure_iter_capture_names_next(mPtr.get(), &next)) {
+      return Some(next);
+    }
+    return Nothing();
+  }
+
+ private:
+  friend class RustRegex;
+
+  explicit RustRegexIterCaptureNames(rure* aRe)
+      : mPtr(aRe ? rure_iter_capture_names_new(aRe) : nullptr) {}
+
+  struct Deleter {
+    void operator()(rure_iter_capture_names* ptr) const {
+      rure_iter_capture_names_free(ptr);
+    }
+  };
+  UniquePtr<rure_iter_capture_names, Deleter> mPtr;
+};
+
+/*
+ * RustRegexIter is an iterator over successive non-overlapping matches in a
+ * particular haystack.
+ *
+ * A RustRegexIter value may not outlive its corresponding RustRegex and should
+ * be destroyed before its corresponding RustRegex is destroyed.
+ *
+ * It is not safe to use from multiple threads simultaneously.
+ */
+class RustRegexIter {
+ public:
+  RustRegexIter() = delete;
+
+  // Check if the `RustRegexIter` object is valid.
+  bool IsValid() const { return mPtr != nullptr; }
+  explicit operator bool() const { return IsValid(); }
+
+  /*
+   * Next() returns Some if and only if this regex matches anywhere in haystack.
+   * The returned RustRegexMatch object contains the start and end offsets (in
+   * bytes) of the match.
+   *
+   * If no match is found, then subsequent calls will return Nothing()
+   * indefinitely.
+   *
+   * Next() should be preferred to NextCaptures() since it may be faster.
+   *
+   * N.B. The performance of this search is not impacted by the presence of
+   * capturing groups in your regular expression.
+   */
+  mozilla::Maybe<RustRegexMatch> Next() {
+    RustRegexMatch match{};
+    if (mPtr &&
+        rure_iter_next(mPtr.get(), mHaystackPtr, mHaystackSize, &match)) {
+      return Some(match);
+    }
+    return Nothing();
+  }
+
+  /*
+   * NextCaptures returns a valid RustRegexCaptures if and only if this regex
+   * matches anywhere in haystack. If a match is found, then all of its capture
+   * locations are stored in the returned RustRegexCaptures object.
+   *
+   * If no match is found, then subsequent calls will return an invalid
+   * `RustRegexCaptures` indefinitely.
+   *
+   * Only use this function if you specifically need access to capture
+   * locations. It is not necessary to use this function just because your
+   * regular expression contains capturing groups.
+   *
+   * Capture locations can be accessed using the methods on RustRegexCaptures.
+   *
+   * N.B. The performance of this search can be impacted by the number of
+   * capturing groups. If you're using this function, it may be beneficial to
+   * use non-capturing groups (e.g., `(?:re)`) where possible.
+   */
+  RustRegexCaptures NextCaptures() {
+    RustRegexCaptures captures(mRe);
+    if (mPtr && rure_iter_next_captures(mPtr.get(), mHaystackPtr, mHaystackSize,
+                                        captures.mPtr.get())) {
+      return captures;
+    }
+    return {};
+  }
+
+ private:
+  friend class RustRegex;
+  RustRegexIter(rure* aRe, const std::string_view& aHaystack)
+      : mRe(aRe),
+        mHaystackPtr(reinterpret_cast<const uint8_t*>(aHaystack.data())),
+        mHaystackSize(aHaystack.size()),
+        mPtr(aRe ? rure_iter_new(aRe) : nullptr) {}
+
+  rure* MOZ_NON_OWNING_REF mRe;
+  const uint8_t* MOZ_NON_OWNING_REF mHaystackPtr;
+  size_t mHaystackSize;
+
+  struct Deleter {
+    void operator()(rure_iter* ptr) const { rure_iter_free(ptr); }
+  };
+  UniquePtr<rure_iter, Deleter> mPtr;
+};
+
+/*
+ * RustRegexOptions is the set of configuration options for compiling a regular
+ * expression.
+ *
+ * All flags on this type can be used to set default flags while compiling, and
+ * can be toggled in the expression itself using standard syntax, e.g. `(?i)`
+ * turns case-insensitive matching on, and `(?-i)` disables it.
+ *
+ * In addition, two non-flag options are available: setting the size limit of
+ * the compiled program and setting the size limit of the cache of states that
+ * the DFA uses while searching.
+ *
+ * For most uses, the default settings will work fine, and a default-constructed
+ * RustRegexOptions can be passed.
+ */
+class RustRegexOptions {
+ public:
+  RustRegexOptions() = default;
+
+  /*
+   * Set the value for the case insensitive (i) flag.
+   *
+   * When enabled, letters in the pattern will match both upper case and lower
+   * case variants.
+   */
+  RustRegexOptions& CaseInsensitive(bool aYes) {
+    return SetFlag(aYes, RURE_FLAG_CASEI);
+  }
+
+  /*
+   * Set the value for the multi-line matching (m) flag.
+   *
+   * When enabled, ^ matches the beginning of lines and $ matches the end of
+   * lines.
+   *
+   * By default, they match beginning/end of the input.
+   */
+  RustRegexOptions& MultiLine(bool aYes) {
+    return SetFlag(aYes, RURE_FLAG_MULTI);
+  }
+
+  /*
+   * Set the value for the any character (s) flag, where in . matches anything
+   * when s is set and matches anything except for new line when it is not set
+   * (the default).
+   *
+   * N.B. “matches anything” means “any byte” when Unicode is disabled and means
+   * “any valid UTF-8 encoding of any Unicode scalar value” when Unicode is
+   * enabled.
+   */
+  RustRegexOptions& DotMatchesNewLine(bool aYes) {
+    return SetFlag(aYes, RURE_FLAG_DOTNL);
+  }
+
+  /*
+   * Set the value for the greedy swap (U) flag.
+   *
+   * When enabled, a pattern like a* is lazy (tries to find shortest match) and
+   * a*? is greedy (tries to find longest match).
+   *
+   * By default, a* is greedy and a*? is lazy.
+   */
+  RustRegexOptions& SwapGreed(bool aYes) {
+    return SetFlag(aYes, RURE_FLAG_SWAP_GREED);
+  }
+
+  /*
+   * Set the value for the ignore whitespace (x) flag.
+   *
+   * When enabled, whitespace such as new lines and spaces will be ignored
+   * between expressions of the pattern, and # can be used to start a comment
+   * until the next new line.
+   */
+  RustRegexOptions& IgnoreWhitespace(bool aYes) {
+    return SetFlag(aYes, RURE_FLAG_SPACE);
+  }
+
+  /*
+   * Set the value for the Unicode (u) flag.
+   *
+   * Enabled by default. When disabled, character classes such as \w only match
+   * ASCII word characters instead of all Unicode word characters.
+   */
+  RustRegexOptions& Unicode(bool aYes) {
+    return SetFlag(aYes, RURE_FLAG_UNICODE);
+  }
+
+  /*
+   * SizeLimit sets the appoximate size limit of the compiled regular
+   * expression.
+   *
+   * This size limit roughly corresponds to the number of bytes occupied by
+   * a single compiled program. If the program would exceed this number,
+   * then an invalid RustRegex will be constructed.
+   */
+  RustRegexOptions& SizeLimit(size_t aLimit) {
+    mSizeLimit = Some(aLimit);
+    return *this;
+  }
+
+  /*
+   * DFASizeLimit sets the approximate size of the cache used by the DFA during
+   * search.
+   *
+   * This roughly corresponds to the number of bytes that the DFA will use while
+   * searching.
+   *
+   * Note that this is a *per thread* limit. There is no way to set a global
+   * limit. In particular, if a regular expression is used from multiple threads
+   * simultaneously, then each thread may use up to the number of bytes
+   * specified here.
+   */
+  RustRegexOptions& DFASizeLimit(size_t aLimit) {
+    mDFASizeLimit = Some(aLimit);
+    return *this;
+  }
+
+ private:
+  friend class RustRegex;
+  friend class RustRegexSet;
+
+  struct OptionsDeleter {
+    void operator()(rure_options* ptr) const { rure_options_free(ptr); }
+  };
+
+  UniquePtr<rure_options, OptionsDeleter> GetOptions() const {
+    UniquePtr<rure_options, OptionsDeleter> options;
+    if (mSizeLimit || mDFASizeLimit) {
+      options.reset(rure_options_new());
+      if (mSizeLimit) {
+        rure_options_size_limit(options.get(), *mSizeLimit);
+      }
+      if (mDFASizeLimit) {
+        rure_options_dfa_size_limit(options.get(), *mDFASizeLimit);
+      }
+    }
+    return options;
+  }
+
+  uint32_t GetFlags() const { return mFlags; }
+
+  RustRegexOptions& SetFlag(bool aYes, uint32_t aFlag) {
+    if (aYes) {
+      mFlags |= aFlag;
+    } else {
+      mFlags &= ~aFlag;
+    }
+    return *this;
+  }
+
+  uint32_t mFlags = RURE_DEFAULT_FLAGS;
+  Maybe<size_t> mSizeLimit;
+  Maybe<size_t> mDFASizeLimit;
+};
+
+/*
+ * RustRegex is the type of a compiled regular expression.
+ *
+ * A RustRegex can be safely used from multiple threads simultaneously.
+ *
+ * When calling the matching methods on this type, they will generally have the
+ * following parameters:
+ *
+ * aHaystack
+ *   may contain arbitrary bytes, but ASCII compatible text is more useful.
+ *   UTF-8 is even more useful. Other text encodings aren't supported.
+ *
+ * aStart
+ *   the position in bytes at which to start searching. Note that setting the
+ *   start position is distinct from using a substring for `aHaystack`, since
+ *   the regex engine may look at bytes before the start position to determine
+ *   match information. For example, if the start position is greater than 0,
+ *   then the \A ("begin text") anchor can never match.
+ */
+class RustRegex final {
+ public:
+  // Create a new invalid RustRegex object
+  RustRegex() = default;
+
+  /*
+   * Compiles the given pattern into a regular expression. The pattern must be
+   * valid UTF-8 and the length corresponds to the number of bytes in the
+   * pattern.
+   *
+   * If an error occurs, the constructed RustRegex will be `!IsValid()`.
+   *
+   * The compiled expression returned may be used from multiple threads
+   * simultaneously.
+   */
+  explicit RustRegex(const std::string_view& aPattern,
+                     const RustRegexOptions& aOptions = {}) {
+#ifdef DEBUG
+    rure_error* error = rure_error_new();
+#else
+    rure_error* error = nullptr;
+#endif
+    mPtr.reset(rure_compile(reinterpret_cast<const uint8_t*>(aPattern.data()),
+                            aPattern.size(), aOptions.GetFlags(),
+                            aOptions.GetOptions().get(), error));
+#ifdef DEBUG
+    if (!mPtr) {
+      NS_WARNING(nsPrintfCString("RustRegex compile failed: %s",
+                                 rure_error_message(error))
+                     .get());
+    }
+    rure_error_free(error);
+#endif
+  }
+
+  // Check if the compiled `RustRegex` is valid.
+  bool IsValid() const { return mPtr != nullptr; }
+  explicit operator bool() const { return IsValid(); }
+
+  /*
+   * IsMatch returns true if and only if this regex matches anywhere in
+   * aHaystack.
+   *
+   * See the type-level comment for details on aHaystack and aStart.
+   *
+   * IsMatch() should be preferred to Find() since it may be faster.
+   *
+   * N.B. The performance of this search is not impacted by the presence of
+   * capturing groups in your regular expression.
+   */
+  bool IsMatch(const std::string_view& aHaystack, size_t aStart = 0) const {
+    return mPtr &&
+           rure_is_match(mPtr.get(),
+                         reinterpret_cast<const uint8_t*>(aHaystack.data()),
+                         aHaystack.size(), aStart);
+  }
+
+  /*
+   * Find returns Some if and only if this regex matches anywhere in
+   * haystack. The returned RustRegexMatch object contains the start and end
+   * offsets (in bytes) of the match.
+   *
+   * See the type-level comment for details on aHaystack and aStart.
+   *
+   * Find() should be preferred to FindCaptures() since it may be faster.
+   *
+   * N.B. The performance of this search is not impacted by the presence of
+   * capturing groups in your regular expression.
+   */
+  Maybe<RustRegexMatch> Find(const std::string_view& aHaystack,
+                             size_t aStart = 0) const {
+    RustRegexMatch match{};
+    if (mPtr && rure_find(mPtr.get(),
+                          reinterpret_cast<const uint8_t*>(aHaystack.data()),
+                          aHaystack.size(), aStart, &match)) {
+      return Some(match);
+    }
+    return Nothing();
+  }
+
+  /*
+   * FindCaptures() returns a valid RustRegexCaptures if and only if this
+   * regex matches anywhere in haystack. If a match is found, then all of its
+   * capture locations are stored in the returned RustRegexCaptures object.
+   *
+   * See the type-level comment for details on aHaystack and aStart.
+   *
+   * Only use this function if you specifically need access to capture
+   * locations. It is not necessary to use this function just because your
+   * regular expression contains capturing groups.
+   *
+   * Capture locations can be accessed using the methods on RustRegexCaptures.
+   *
+   * N.B. The performance of this search can be impacted by the number of
+   * capturing groups. If you're using this function, it may be beneficial to
+   * use non-capturing groups (e.g., `(?:re)`) where possible.
+   */
+  RustRegexCaptures FindCaptures(const std::string_view& aHaystack,
+                                 size_t aStart = 0) const {
+    RustRegexCaptures captures(mPtr.get());
+    if (mPtr &&
+        rure_find_captures(mPtr.get(),
+                           reinterpret_cast<const uint8_t*>(aHaystack.data()),
+                           aHaystack.size(), aStart, captures.mPtr.get())) {
+      return captures;
+    }
+    return {};
+  }
+
+  /*
+   * ShortestMatch() returns Some if and only if this regex matches anywhere
+   * in haystack. If a match is found, then its end location is stored in the
+   * pointer given. The end location is the place at which the regex engine
+   * determined that a match exists, but may occur before the end of the
+   * proper leftmost-first match.
+   *
+   * See the type-level comment for details on aHaystack and aStart.
+   *
+   * ShortestMatch should be preferred to Find since it may be faster.
+   *
+   * N.B. The performance of this search is not impacted by the presence of
+   * capturing groups in your regular expression.
+   */
+  Maybe<size_t> ShortestMatch(const std::string_view& aHaystack,
+                              size_t aStart = 0) const {
+    size_t end = 0;
+    if (mPtr &&
+        rure_shortest_match(mPtr.get(),
+                            reinterpret_cast<const uint8_t*>(aHaystack.data()),
+                            aHaystack.size(), aStart, &end)) {
+      return Some(end);
+    }
+    return Nothing();
+  }
+
+  /*
+   * Create an iterator over all successive non-overlapping matches of this
+   * regex in aHaystack.
+   *
+   * See the type-level comment for details on aHaystack.
+   *
+   * Both aHaystack and this regex must remain valid until the returned
+   * `RustRegexIter` is destroyed.
+   */
+  RustRegexIter IterMatches(const std::string_view& aHaystack) const {
+    return RustRegexIter(mPtr.get(), aHaystack);
+  }
+
+  /*
+   * Returns the capture index for the name given. If no such named capturing
+   * group exists in this regex, then -1 is returned.
+   *
+   * The capture index may be used with RustRegexCaptures::CaptureAt.
+   *
+   * This function never returns 0 since the first capture group always
+   * corresponds to the entire match and is always unnamed.
+   */
+  int32_t CaptureNameIndex(const char* aName) const {
+    return mPtr ? rure_capture_name_index(mPtr.get(), aName) : -1;
+  }
+
+  /*
+   * Create an iterator over the list of capture group names in this particular
+   * regex.
+   *
+   * This regex must remain valid until the returned `RustRegexIterCaptureNames`
+   * is destroyed.
+   */
+  RustRegexIterCaptureNames IterCaptureNames() const {
+    return RustRegexIterCaptureNames(mPtr.get());
+  }
+
+  /*
+   * Count the number of successive non-overlapping matches of this regex in
+   * aHaystack.
+   *
+   * See the type-level comment for details on aHaystack.
+   */
+  size_t CountMatches(const std::string_view& aHaystack) const {
+    size_t count = 0;
+    auto iter = IterMatches(aHaystack);
+    while (iter.Next()) {
+      count++;
+    }
+    return count;
+  }
+
+ private:
+  struct Deleter {
+    void operator()(rure* ptr) const { rure_free(ptr); }
+  };
+  UniquePtr<rure, Deleter> mPtr;
+};
+
+/*
+ * RustRegexSet is the type of a set of compiled regular expression.
+ *
+ * A RustRegexSet can be safely used from multiple threads simultaneously.
+ *
+ * When calling the matching methods on this type, they will generally have the
+ * following parameters:
+ *
+ * aHaystack
+ *   may contain arbitrary bytes, but ASCII compatible text is more useful.
+ *   UTF-8 is even more useful. Other text encodings aren't supported.
+ *
+ * aStart
+ *   the position in bytes at which to start searching. Note that setting the
+ *   start position is distinct from using a substring for `aHaystack`, since
+ *   the regex engine may look at bytes before the start position to determine
+ *   match information. For example, if the start position is greater than 0,
+ *   then the \A ("begin text") anchor can never match.
+ */
+class RustRegexSet final {
+ public:
+  /*
+   * Compiles the given range of patterns into a single regular expression which
+   * can be matched in a linear-scan. Each pattern in aPatterns must be valid
+   * UTF-8, and implicitly coerce to `std::string_view`.
+   *
+   * If an error occurs, the constructed RustRegexSet will be `!IsValid()`.
+   *
+   * The compiled expression returned may be used from multiple threads
+   * simultaneously.
+   */
+  template <typename Patterns>
+  explicit RustRegexSet(Patterns&& aPatterns,
+                        const RustRegexOptions& aOptions = {}) {
+#ifdef DEBUG
+    rure_error* error = rure_error_new();
+#else
+    rure_error* error = nullptr;
+#endif
+    AutoTArray<const uint8_t*, 4> patternPtrs;
+    AutoTArray<size_t, 4> patternSizes;
+    for (auto&& pattern : std::forward<Patterns>(aPatterns)) {
+      std::string_view view = pattern;
+      patternPtrs.AppendElement(reinterpret_cast<const uint8_t*>(view.data()));
+      patternSizes.AppendElement(view.size());
+    }
+    mPtr.reset(rure_compile_set(patternPtrs.Elements(), patternSizes.Elements(),
+                                patternPtrs.Length(), aOptions.GetFlags(),
+                                aOptions.GetOptions().get(), error));
+#ifdef DEBUG
+    if (!mPtr) {
+      NS_WARNING(nsPrintfCString("RustRegexSet compile failed: %s",
+                                 rure_error_message(error))
+                     .get());
+    }
+    rure_error_free(error);
+#endif
+  }
+
+  // Check if the `RustRegexSet` object is valid.
+  bool IsValid() const { return mPtr != nullptr; }
+  explicit operator bool() const { return IsValid(); }
+
+  /*
+   * IsMatch returns true if and only if any regexes within the set
+   * match anywhere in the haystack. Once a match has been located, the
+   * matching engine will quit immediately.
+   *
+   * See the type-level comment for details on aHaystack and aStart.
+   */
+  bool IsMatch(const std::string_view& aHaystack, size_t aStart = 0) const {
+    return mPtr &&
+           rure_set_is_match(mPtr.get(),
+                             reinterpret_cast<const uint8_t*>(aHaystack.data()),
+                             aHaystack.size(), aStart);
+  }
+
+  struct SetMatches {
+    bool matchedAny = false;
+    nsTArray<bool> matches;
+  };
+
+  /*
+   * Matches() compares each regex in the set against the haystack and
+   * returns a list with the match result of each pattern. Match results are
+   * ordered in the same way as the regex set was compiled. For example, index 0
+   * of matches corresponds to the first pattern passed to the constructor.
+   *
+   * See the type-level comment for details on aHaystack and aStart.
+   *
+   * Only use this function if you specifically need to know which regexes
+   * matched within the set. To determine if any of the regexes matched without
+   * caring which, use IsMatch.
+   */
+  SetMatches Matches(const std::string_view& aHaystack,
+                     size_t aStart = 0) const {
+    nsTArray<bool> matches;
+    matches.SetLength(Length());
+    bool any = mPtr && rure_set_matches(
+                           mPtr.get(),
+                           reinterpret_cast<const uint8_t*>(aHaystack.data()),
+                           aHaystack.size(), aStart, matches.Elements());
+    return SetMatches{any, std::move(matches)};
+  }
+
+  /*
+   * Returns the number of patterns the regex set was compiled with.
+   */
+  size_t Length() const { return mPtr ? rure_set_len(mPtr.get()) : 0; }
+
+ private:
+  struct Deleter {
+    void operator()(rure_set* ptr) const { rure_set_free(ptr); }
+  };
+  UniquePtr<rure_set, Deleter> mPtr;
+};
+
+}  // namespace mozilla
+
+#endif  // mozilla_RustRegex_h