1 files changed, 117 insertions, 0 deletions
diff --git a/xpcom/string/nsStringIterator.h b/xpcom/string/nsStringIterator.h
new file mode 100644
index 0000000000..db14efdaca
--- /dev/null
+++ b/xpcom/string/nsStringIterator.h
@@ -0,0 +1,117 @@
+/* -*- 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 nsStringIterator_h___
+#define nsStringIterator_h___
+
+#include "nsCharTraits.h"
+#include "nsAlgorithm.h"
+#include "nsDebug.h"
+
+/**
+ * @see nsTAString
+ */
+
+template <class CharT>
+class nsReadingIterator {
+ public:
+  typedef nsReadingIterator<CharT> self_type;
+  typedef ptrdiff_t difference_type;
+  typedef size_t size_type;
+  typedef CharT value_type;
+  typedef const CharT* pointer;
+  typedef const CharT& reference;
+
+ private:
+  friend class mozilla::detail::nsTStringRepr<CharT>;
+
+  // unfortunately, the API for nsReadingIterator requires that the
+  // iterator know its start and end positions.  this was needed when
+  // we supported multi-fragment strings, but now it is really just
+  // extra baggage.  we should remove mStart and mEnd at some point.
+
+  const CharT* mStart;
+  const CharT* mEnd;
+  const CharT* mPosition;
+
+ public:
+  nsReadingIterator() : mStart(nullptr), mEnd(nullptr), mPosition(nullptr) {}
+  // clang-format off
+  // nsReadingIterator( const nsReadingIterator<CharT>& );                    // auto-generated copy-constructor OK
+  // nsReadingIterator<CharT>& operator=( const nsReadingIterator<CharT>& );  // auto-generated copy-assignment operator OK
+  // clang-format on
+
+  pointer get() const { return mPosition; }
+
+  CharT operator*() const { return *get(); }
+
+  self_type& operator++() {
+    ++mPosition;
+    return *this;
+  }
+
+  self_type operator++(int) {
+    self_type result(*this);
+    ++mPosition;
+    return result;
+  }
+
+  self_type& operator--() {
+    --mPosition;
+    return *this;
+  }
+
+  self_type operator--(int) {
+    self_type result(*this);
+    --mPosition;
+    return result;
+  }
+
+  self_type& advance(difference_type aN) {
+    if (aN > 0) {
+      difference_type step = XPCOM_MIN(aN, mEnd - mPosition);
+
+      NS_ASSERTION(
+          step > 0,
+          "can't advance a reading iterator beyond the end of a string");
+
+      mPosition += step;
+    } else if (aN < 0) {
+      difference_type step = XPCOM_MAX(aN, -(mPosition - mStart));
+
+      NS_ASSERTION(step < 0,
+                   "can't advance (backward) a reading iterator beyond the end "
+                   "of a string");
+
+      mPosition += step;
+    }
+    return *this;
+  }
+
+  // We return an unsigned type here (with corresponding assert) rather than
+  // the more usual difference_type because we want to make this class go
+  // away in favor of mozilla::RangedPtr.  Since RangedPtr has the same
+  // requirement we are enforcing here, the transition ought to be much
+  // smoother.
+  size_type operator-(const self_type& aOther) const {
+    MOZ_ASSERT(mPosition >= aOther.mPosition);
+    return mPosition - aOther.mPosition;
+  }
+};
+
+template <class CharT>
+inline bool operator==(const nsReadingIterator<CharT>& aLhs,
+                       const nsReadingIterator<CharT>& aRhs) {
+  return aLhs.get() == aRhs.get();
+}
+
+template <class CharT>
+inline bool operator!=(const nsReadingIterator<CharT>& aLhs,
+                       const nsReadingIterator<CharT>& aRhs) {
+  return aLhs.get() != aRhs.get();
+}
+
+#endif /* !defined(nsStringIterator_h___) */