1 files changed, 42 insertions, 0 deletions
diff --git a/layout/base/nsBidi.cpp b/layout/base/nsBidi.cpp
new file mode 100644
index 0000000000..25054f322a
--- /dev/null
+++ b/layout/base/nsBidi.cpp
@@ -0,0 +1,42 @@
+/* -*- 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 "nsBidi.h"
+
+nsresult nsBidi::CountRuns(int32_t* aRunCount) {
+  UErrorCode errorCode = U_ZERO_ERROR;
+  *aRunCount = ubidi_countRuns(mBiDi, &errorCode);
+  if (U_SUCCESS(errorCode)) {
+    mLength = ubidi_getProcessedLength(mBiDi);
+    mLevels = mLength > 0 ? ubidi_getLevels(mBiDi, &errorCode) : nullptr;
+  }
+  return ICUUtils::UErrorToNsResult(errorCode);
+}
+
+void nsBidi::GetLogicalRun(int32_t aLogicalStart, int32_t* aLogicalLimit,
+                           nsBidiLevel* aLevel) {
+  MOZ_ASSERT(mLevels, "CountRuns hasn't been run?");
+  MOZ_RELEASE_ASSERT(aLogicalStart < mLength, "Out of bound");
+  // This function implements an alternative approach to get logical
+  // run that is based on levels of characters, which would avoid O(n^2)
+  // performance issue when used in a loop over runs.
+  // Per comment in ubidi_getLogicalRun, that function doesn't use this
+  // approach because levels have special interpretation when reordering
+  // mode is UBIDI_REORDER_RUNS_ONLY. Since we don't use this mode in
+  // Gecko, it should be safe to just use levels for this function.
+  MOZ_ASSERT(ubidi_getReorderingMode(mBiDi) != UBIDI_REORDER_RUNS_ONLY,
+             "Don't support UBIDI_REORDER_RUNS_ONLY mode");
+
+  nsBidiLevel level = mLevels[aLogicalStart];
+  int32_t limit;
+  for (limit = aLogicalStart + 1; limit < mLength; limit++) {
+    if (mLevels[limit] != level) {
+      break;
+    }
+  }
+  *aLogicalLimit = limit;
+  *aLevel = level;
+}