1 files changed, 138 insertions, 0 deletions
diff --git a/intl/components/src/Bidi.cpp b/intl/components/src/Bidi.cpp
new file mode 100644
index 0000000000..2ce355c8eb
--- /dev/null
+++ b/intl/components/src/Bidi.cpp
@@ -0,0 +1,138 @@
+/* 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 "mozilla/intl/Bidi.h"
+#include "mozilla/Casting.h"
+#include "mozilla/intl/ICU4CGlue.h"
+
+#include "unicode/ubidi.h"
+
+namespace mozilla::intl {
+
+Bidi::Bidi() { mBidi = ubidi_open(); }
+Bidi::~Bidi() { ubidi_close(mBidi.GetMut()); }
+
+ICUResult Bidi::SetParagraph(Span<const char16_t> aParagraph,
+                             BidiEmbeddingLevel aLevel) {
+  // Do not allow any reordering of the runs, as this can change the
+  // performance characteristics of working with runs. In the default mode,
+  // the levels can be iterated over directly, rather than relying on computing
+  // logical runs on the fly. This can have negative performance characteristics
+  // compared to iterating over the levels.
+  //
+  // In the UBIDI_REORDER_RUNS_ONLY the levels are encoded with additional
+  // information which can be safely ignored in this Bidi implementation.
+  // Note that this check is here since setting the mode must be done before
+  // calls to setting the paragraph.
+  MOZ_ASSERT(ubidi_getReorderingMode(mBidi.GetMut()) == UBIDI_REORDER_DEFAULT);
+
+  UErrorCode status = U_ZERO_ERROR;
+  ubidi_setPara(mBidi.GetMut(), aParagraph.Elements(),
+                AssertedCast<int32_t>(aParagraph.Length()), aLevel, nullptr,
+                &status);
+
+  mLevels = nullptr;
+
+  return ToICUResult(status);
+}
+
+Bidi::ParagraphDirection Bidi::GetParagraphDirection() const {
+  switch (ubidi_getDirection(mBidi.GetConst())) {
+    case UBIDI_LTR:
+      return Bidi::ParagraphDirection::LTR;
+    case UBIDI_RTL:
+      return Bidi::ParagraphDirection::RTL;
+    case UBIDI_MIXED:
+      return Bidi::ParagraphDirection::Mixed;
+    case UBIDI_NEUTRAL:
+      // This is only used in `ubidi_getBaseDirection` which is unused in this
+      // API.
+      MOZ_ASSERT_UNREACHABLE("Unexpected UBiDiDirection value.");
+  };
+  return Bidi::ParagraphDirection::Mixed;
+}
+
+/* static */
+void Bidi::ReorderVisual(const BidiEmbeddingLevel* aLevels, int32_t aLength,
+                         int32_t* aIndexMap) {
+  ubidi_reorderVisual(reinterpret_cast<const uint8_t*>(aLevels), aLength,
+                      aIndexMap);
+}
+
+/* static */
+Bidi::BaseDirection Bidi::GetBaseDirection(Span<const char16_t> aParagraph) {
+  UBiDiDirection direction = ubidi_getBaseDirection(
+      aParagraph.Elements(), AssertedCast<int32_t>(aParagraph.Length()));
+
+  switch (direction) {
+    case UBIDI_LTR:
+      return Bidi::BaseDirection::LTR;
+    case UBIDI_RTL:
+      return Bidi::BaseDirection::RTL;
+    case UBIDI_NEUTRAL:
+      return Bidi::BaseDirection::Neutral;
+    case UBIDI_MIXED:
+      MOZ_ASSERT_UNREACHABLE("Unexpected UBiDiDirection value.");
+  }
+
+  return Bidi::BaseDirection::Neutral;
+}
+
+static BidiDirection ToBidiDirection(UBiDiDirection aDirection) {
+  switch (aDirection) {
+    case UBIDI_LTR:
+      return BidiDirection::LTR;
+    case UBIDI_RTL:
+      return BidiDirection::RTL;
+    case UBIDI_MIXED:
+    case UBIDI_NEUTRAL:
+      MOZ_ASSERT_UNREACHABLE("Unexpected UBiDiDirection value.");
+  }
+  return BidiDirection::LTR;
+}
+
+Result<int32_t, ICUError> Bidi::CountRuns() {
+  UErrorCode status = U_ZERO_ERROR;
+  int32_t runCount = ubidi_countRuns(mBidi.GetMut(), &status);
+  if (U_FAILURE(status)) {
+    return Err(ToICUError(status));
+  }
+
+  mLength = ubidi_getProcessedLength(mBidi.GetConst());
+  mLevels = mLength > 0 ? reinterpret_cast<const BidiEmbeddingLevel*>(
+                              ubidi_getLevels(mBidi.GetMut(), &status))
+                        : nullptr;
+  if (U_FAILURE(status)) {
+    return Err(ToICUError(status));
+  }
+
+  return runCount;
+}
+
+void Bidi::GetLogicalRun(int32_t aLogicalStart, int32_t* aLogicalLimitOut,
+                         BidiEmbeddingLevel* aLevelOut) {
+  MOZ_ASSERT(mLevels, "CountRuns hasn't been run?");
+  MOZ_RELEASE_ASSERT(aLogicalStart < mLength, "Out of bound");
+  BidiEmbeddingLevel level = mLevels[aLogicalStart];
+  int32_t limit;
+  for (limit = aLogicalStart + 1; limit < mLength; limit++) {
+    if (mLevels[limit] != level) {
+      break;
+    }
+  }
+  *aLogicalLimitOut = limit;
+  *aLevelOut = level;
+}
+
+BidiEmbeddingLevel Bidi::GetParagraphEmbeddingLevel() const {
+  return BidiEmbeddingLevel(ubidi_getParaLevel(mBidi.GetConst()));
+}
+
+BidiDirection Bidi::GetVisualRun(int32_t aRunIndex, int32_t* aLogicalStart,
+                                 int32_t* aLength) {
+  return ToBidiDirection(
+      ubidi_getVisualRun(mBidi.GetMut(), aRunIndex, aLogicalStart, aLength));
+}
+
+}  // namespace mozilla::intl