1 files changed, 89 insertions, 0 deletions
diff --git a/xpcom/string/nsTSubstringTuple.h b/xpcom/string/nsTSubstringTuple.h
new file mode 100644
index 0000000000..dff8dedca9
--- /dev/null
+++ b/xpcom/string/nsTSubstringTuple.h
@@ -0,0 +1,89 @@
+/* -*- 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/. */
+// IWYU pragma: private, include "nsString.h"
+
+#ifndef nsTSubstringTuple_h
+#define nsTSubstringTuple_h
+
+#include "mozilla/Attributes.h"
+#include "nsTStringRepr.h"
+
+/**
+ * nsTSubstringTuple
+ *
+ * Represents a tuple of string fragments.  Built as a recursive binary tree.
+ * It is used to implement the concatenation of two or more string objects.
+ *
+ * NOTE: This class is a private implementation detail and should never be
+ * referenced outside the string code.
+ */
+template <typename T>
+class MOZ_TEMPORARY_CLASS nsTSubstringTuple {
+ public:
+  typedef T char_type;
+  typedef nsCharTraits<char_type> char_traits;
+
+  typedef nsTSubstringTuple<T> self_type;
+  typedef mozilla::detail::nsTStringRepr<char_type> base_string_type;
+  typedef size_t size_type;
+
+ public:
+  nsTSubstringTuple(const base_string_type* aStrA,
+                    const base_string_type* aStrB)
+      : mHead(nullptr), mFragA(aStrA), mFragB(aStrB) {}
+
+  nsTSubstringTuple(const self_type& aHead, const base_string_type* aStrB)
+      : mHead(&aHead),
+        mFragA(nullptr),  // this fragment is ignored when aHead != nullptr
+        mFragB(aStrB) {}
+
+  /**
+   * computes the aggregate string length
+   */
+  size_type Length() const;
+
+  /**
+   * writes the aggregate string to the given buffer.  bufLen is assumed
+   * to be equal to or greater than the value returned by the Length()
+   * method.  the string written to |buf| is not null-terminated.
+   */
+  void WriteTo(char_type* aBuf, size_type aBufLen) const;
+
+  /**
+   * returns true if this tuple is dependent on (i.e., overlapping with)
+   * the given char sequence.
+   */
+  bool IsDependentOn(const char_type* aStart, const char_type* aEnd) const;
+
+  /**
+   * returns a pair of the results of IsDependentOn() and Length(). This is more
+   * efficient than calling both functions subsequently, as this traverses the
+   * tree only once.
+   */
+  std::pair<bool, size_type> IsDependentOnWithLength(
+      const char_type* aStart, const char_type* aEnd) const;
+
+ private:
+  const self_type* const mHead;
+  const base_string_type* const mFragA;
+  const base_string_type* const mFragB;
+};
+
+template <typename T>
+inline const nsTSubstringTuple<T> operator+(
+    const mozilla::detail::nsTStringRepr<T>& aStrA,
+    const mozilla::detail::nsTStringRepr<T>& aStrB) {
+  return nsTSubstringTuple<T>(&aStrA, &aStrB);
+}
+
+template <typename T>
+inline const nsTSubstringTuple<T> operator+(
+    const nsTSubstringTuple<T>& aHead,
+    const mozilla::detail::nsTStringRepr<T>& aStrB) {
+  return nsTSubstringTuple<T>(aHead, &aStrB);
+}
+
+#endif