1 files changed, 92 insertions, 0 deletions
diff --git a/xpcom/string/nsTSubstringTuple.cpp b/xpcom/string/nsTSubstringTuple.cpp
new file mode 100644
index 0000000000..3219cb19fa
--- /dev/null
+++ b/xpcom/string/nsTSubstringTuple.cpp
@@ -0,0 +1,92 @@
+/* -*- 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/. */
+
+#include "nsTSubstringTuple.h"
+#include "mozilla/CheckedInt.h"
+
+/**
+ * computes the aggregate string length
+ */
+
+template <typename T>
+typename nsTSubstringTuple<T>::size_type nsTSubstringTuple<T>::Length() const {
+  mozilla::CheckedInt<size_type> len;
+  if (mHead) {
+    len = mHead->Length();
+  } else {
+    len = mFragA->Length();
+  }
+
+  len += mFragB->Length();
+  MOZ_RELEASE_ASSERT(len.isValid(), "Substring tuple length is invalid");
+  return len.value();
+}
+
+/**
+ * writes the aggregate string to the given buffer. aBufLen is assumed
+ * to be equal to or greater than the value returned by the Length()
+ * method.  the string written to |aBuf| is not null-terminated.
+ */
+
+template <typename T>
+void nsTSubstringTuple<T>::WriteTo(char_type* aBuf, size_type aBufLen) const {
+  MOZ_RELEASE_ASSERT(aBufLen >= mFragB->Length(), "buffer too small");
+  size_type headLen = aBufLen - mFragB->Length();
+  if (mHead) {
+    mHead->WriteTo(aBuf, headLen);
+  } else {
+    MOZ_RELEASE_ASSERT(mFragA->Length() == headLen, "buffer incorrectly sized");
+    char_traits::copy(aBuf, mFragA->Data(), mFragA->Length());
+  }
+
+  char_traits::copy(aBuf + headLen, mFragB->Data(), mFragB->Length());
+}
+
+/**
+ * returns true if this tuple is dependent on (i.e., overlapping with)
+ * the given char sequence.
+ */
+
+template <typename T>
+bool nsTSubstringTuple<T>::IsDependentOn(const char_type* aStart,
+                                         const char_type* aEnd) const {
+  // we start with the right-most fragment since it is faster to check.
+
+  if (mFragB->IsDependentOn(aStart, aEnd)) {
+    return true;
+  }
+
+  if (mHead) {
+    return mHead->IsDependentOn(aStart, aEnd);
+  }
+
+  return mFragA->IsDependentOn(aStart, aEnd);
+}
+
+template <typename T>
+auto nsTSubstringTuple<T>::IsDependentOnWithLength(const char_type* aStart,
+                                                   const char_type* aEnd) const
+    -> std::pair<bool, size_type> {
+  // we start with the right-most fragment since it is faster to check for
+  // dependency.
+  const bool rightDependentOn = mFragB->IsDependentOn(aStart, aEnd);
+
+  if (rightDependentOn) {
+    return {true, Length()};
+  }
+
+  const auto [leftDependentOn, leftLen] =
+      mHead ? mHead->IsDependentOnWithLength(aStart, aEnd)
+            : std::pair{mFragA->IsDependentOn(aStart, aEnd), mFragA->Length()};
+
+  const auto checkedLen =
+      mozilla::CheckedInt<size_type>{leftLen} + mFragB->Length();
+  MOZ_RELEASE_ASSERT(checkedLen.isValid(), "Substring tuple length is invalid");
+  return {leftDependentOn, checkedLen.value()};
+}
+
+template class nsTSubstringTuple<char>;
+template class nsTSubstringTuple<char16_t>;