intl/components/src/Bidi.cpp

   1 /* This Source Code Form is subject to the terms of the Mozilla Public
   2  * License, v. 2.0. If a copy of the MPL was not distributed with this
   3  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   4
   5 #include "mozilla/intl/Bidi.h"
   6 #include "mozilla/Casting.h"
   7 #include "mozilla/intl/ICU4CGlue.h"
   8
   9 #include "unicode/ubidi.h"
  10
  11 namespace mozilla::intl {
  12
  13 Bidi::Bidi() { mBidi = ubidi_open(); }
  14 Bidi::~Bidi() { ubidi_close(mBidi.GetMut()); }
  15
  16 ICUResult Bidi::SetParagraph(Span<const char16_t> aParagraph,
  17                              BidiEmbeddingLevel aLevel) {
  18   // Do not allow any reordering of the runs, as this can change the
  19   // performance characteristics of working with runs. In the default mode,
  20   // the levels can be iterated over directly, rather than relying on computing
  21   // logical runs on the fly. This can have negative performance characteristics
  22   // compared to iterating over the levels.
  23   //
  24   // In the UBIDI_REORDER_RUNS_ONLY the levels are encoded with additional
  25   // information which can be safely ignored in this Bidi implementation.
  26   // Note that this check is here since setting the mode must be done before
  27   // calls to setting the paragraph.
  28   MOZ_ASSERT(ubidi_getReorderingMode(mBidi.GetMut()) == UBIDI_REORDER_DEFAULT);
  29
  30   UErrorCode status = U_ZERO_ERROR;
  31   ubidi_setPara(mBidi.GetMut(), aParagraph.Elements(),
  32                 AssertedCast<int32_t>(aParagraph.Length()), aLevel, nullptr,
  33                 &status);
  34
  35   mLevels = nullptr;
  36
  37   return ToICUResult(status);
  38 }
  39
  40 Bidi::ParagraphDirection Bidi::GetParagraphDirection() const {
  41   switch (ubidi_getDirection(mBidi.GetConst())) {
  42     case UBIDI_LTR:
  43       return Bidi::ParagraphDirection::LTR;
  44     case UBIDI_RTL:
  45       return Bidi::ParagraphDirection::RTL;
  46     case UBIDI_MIXED:
  47       return Bidi::ParagraphDirection::Mixed;
  48     case UBIDI_NEUTRAL:
  49       // This is only used in `ubidi_getBaseDirection` which is unused in this
  50       // API.
  51       MOZ_ASSERT_UNREACHABLE("Unexpected UBiDiDirection value.");
  52   };
  53   return Bidi::ParagraphDirection::Mixed;
  54 }
  55
  56 /* static */
  57 void Bidi::ReorderVisual(const BidiEmbeddingLevel* aLevels, int32_t aLength,
  58                          int32_t* aIndexMap) {
  59   ubidi_reorderVisual(reinterpret_cast<const uint8_t*>(aLevels), aLength,
  60                       aIndexMap);
  61 }
  62
  63 /* static */
  64 Bidi::BaseDirection Bidi::GetBaseDirection(Span<const char16_t> aParagraph) {
  65   UBiDiDirection direction = ubidi_getBaseDirection(
  66       aParagraph.Elements(), AssertedCast<int32_t>(aParagraph.Length()));
  67
  68   switch (direction) {
  69     case UBIDI_LTR:
  70       return Bidi::BaseDirection::LTR;
  71     case UBIDI_RTL:
  72       return Bidi::BaseDirection::RTL;
  73     case UBIDI_NEUTRAL:
  74       return Bidi::BaseDirection::Neutral;
  75     case UBIDI_MIXED:
  76       MOZ_ASSERT_UNREACHABLE("Unexpected UBiDiDirection value.");
  77   }
  78
  79   return Bidi::BaseDirection::Neutral;
  80 }
  81
  82 static BidiDirection ToBidiDirection(UBiDiDirection aDirection) {
  83   switch (aDirection) {
  84     case UBIDI_LTR:
  85       return BidiDirection::LTR;
  86     case UBIDI_RTL:
  87       return BidiDirection::RTL;
  88     case UBIDI_MIXED:
  89     case UBIDI_NEUTRAL:
  90       MOZ_ASSERT_UNREACHABLE("Unexpected UBiDiDirection value.");
  91   }
  92   return BidiDirection::LTR;
  93 }
  94
  95 Result<int32_t, ICUError> Bidi::CountRuns() {
  96   UErrorCode status = U_ZERO_ERROR;
  97   int32_t runCount = ubidi_countRuns(mBidi.GetMut(), &status);
  98   if (U_FAILURE(status)) {
  99     return Err(ToICUError(status));
 100   }
 101
 102   mLength = ubidi_getProcessedLength(mBidi.GetConst());
 103   mLevels = mLength > 0 ? reinterpret_cast<const BidiEmbeddingLevel*>(
 104                               ubidi_getLevels(mBidi.GetMut(), &status))
 105                         : nullptr;
 106   if (U_FAILURE(status)) {
 107     return Err(ToICUError(status));
 108   }
 109
 110   return runCount;
 111 }
 112
 113 void Bidi::GetLogicalRun(int32_t aLogicalStart, int32_t* aLogicalLimitOut,
 114                          BidiEmbeddingLevel* aLevelOut) {
 115   MOZ_ASSERT(mLevels, "CountRuns hasn't been run?");
 116   MOZ_RELEASE_ASSERT(aLogicalStart < mLength, "Out of bound");
 117   BidiEmbeddingLevel level = mLevels[aLogicalStart];
 118   int32_t limit;
 119   for (limit = aLogicalStart + 1; limit < mLength; limit++) {
 120     if (mLevels[limit] != level) {
 121       break;
 122     }
 123   }
 124   *aLogicalLimitOut = limit;
 125   *aLevelOut = level;
 126 }
 127
 128 BidiEmbeddingLevel Bidi::GetParagraphEmbeddingLevel() const {
 129   return BidiEmbeddingLevel(ubidi_getParaLevel(mBidi.GetConst()));
 130 }
 131
 132 BidiDirection Bidi::GetVisualRun(int32_t aRunIndex, int32_t* aLogicalStart,
 133                                  int32_t* aLength) {
 134   return ToBidiDirection(
 135       ubidi_getVisualRun(mBidi.GetMut(), aRunIndex, aLogicalStart, aLength));
 136 }
 137
 138 }  // namespace mozilla::intl