gecko-dev/intl/lwbrk/WordBreaker.cpp

/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* 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/WordBreaker.h"
#include "mozilla/StaticPrefs_layout.h"
#include "nsComplexBreaker.h"
#include "nsTArray.h"
#include "nsUnicodeProperties.h"

using mozilla::intl::WordBreaker;
using mozilla::intl::WordRange;
using mozilla::unicode::GetGenCategory;
using mozilla::unicode::GetScriptCode;
using mozilla::unicode::Script;

/*static*/
already_AddRefed<WordBreaker> WordBreaker::Create() {
  return RefPtr<WordBreaker>(new WordBreaker()).forget();
}

#define IS_ASCII(c) (0 == (0xFF80 & (c)))
#define ASCII_IS_ALPHA(c) \
  ((('a' <= (c)) && ((c) <= 'z')) || (('A' <= (c)) && ((c) <= 'Z')))
#define ASCII_IS_DIGIT(c) (('0' <= (c)) && ((c) <= '9'))
#define ASCII_IS_SPACE(c) \
  ((' ' == (c)) || ('\t' == (c)) || ('\r' == (c)) || ('\n' == (c)))
#define IS_ALPHABETICAL_SCRIPT(c) ((c) < 0x2E80)

// we change the beginning of IS_HAN from 0x4e00 to 0x3400 to relfect
// Unicode 3.0
#define IS_HAN(c) \
  ((0x3400 <= (c)) && ((c) <= 0x9fff)) || ((0xf900 <= (c)) && ((c) <= 0xfaff))
#define IS_KATAKANA(c) ((0x30A0 <= (c)) && ((c) <= 0x30FF))
#define IS_HIRAGANA(c) ((0x3040 <= (c)) && ((c) <= 0x309F))
#define IS_HALFWIDTHKATAKANA(c) ((0xFF60 <= (c)) && ((c) <= 0xFF9F))

// Return true if aChar belongs to a SEAsian script that is written without
// word spaces, so we need to use the "complex breaker" to find possible word
// boundaries. (https://en.wikipedia.org/wiki/Scriptio_continua)
// (How well this works depends on the level of platform support for finding
// possible line breaks - or possible word boundaries - in the particular
// script. Thai, at least, works pretty well on the major desktop OSes. If
// the script is not supported by the platform, we just won't find any useful
// boundaries.)
static bool IsScriptioContinua(char16_t aChar) {
  Script sc = GetScriptCode(aChar);
  return sc == Script::THAI || sc == Script::MYANMAR || sc == Script::KHMER ||
         sc == Script::JAVANESE || sc == Script::BALINESE ||
         sc == Script::SUNDANESE || sc == Script::LAO;
}

/* static */
WordBreaker::WordBreakClass WordBreaker::GetClass(char16_t c) {
  // begin of the hack

  if (IS_ALPHABETICAL_SCRIPT(c)) {
    if (IS_ASCII(c)) {
      if (ASCII_IS_SPACE(c)) {
        return kWbClassSpace;
      }
      if (ASCII_IS_ALPHA(c) || ASCII_IS_DIGIT(c) ||
          (c == '_' && !StaticPrefs::layout_word_select_stop_at_underscore())) {
        return kWbClassAlphaLetter;
      }
      return kWbClassPunct;
    }
    if (c == 0x00A0 /*NBSP*/) {
      return kWbClassSpace;
    }
    if (GetGenCategory(c) == nsUGenCategory::kPunctuation) {
      return kWbClassPunct;
    }
    if (IsScriptioContinua(c)) {
      return kWbClassScriptioContinua;
    }
    return kWbClassAlphaLetter;
  }
  if (IS_HAN(c)) {
    return kWbClassHanLetter;
  }
  if (IS_KATAKANA(c)) {
    return kWbClassKatakanaLetter;
  }
  if (IS_HIRAGANA(c)) {
    return kWbClassHiraganaLetter;
  }
  if (IS_HALFWIDTHKATAKANA(c)) {
    return kWbClassHWKatakanaLetter;
  }
  if (GetGenCategory(c) == nsUGenCategory::kPunctuation) {
    return kWbClassPunct;
  }
  if (IsScriptioContinua(c)) {
    return kWbClassScriptioContinua;
  }
  return kWbClassAlphaLetter;
}

WordRange WordBreaker::FindWord(const char16_t* aText, uint32_t aLen,
                                uint32_t aPos) {
  MOZ_ASSERT(aText);

  if (aPos >= aLen) {
    return {aLen, aLen};
  }

  WordBreakClass c = GetClass(aText[aPos]);
  WordRange range{0, aLen};

  // Scan forward
  for (uint32_t i = aPos + 1; i <= aLen; i++) {
    if (c != GetClass(aText[i])) {
      range.mEnd = i;
      break;
    }
  }

  // Scan backward
  for (uint32_t i = aPos; i > 0; i--) {
    if (c != GetClass(aText[i - 1])) {
      range.mBegin = i;
      break;
    }
  }

  if (kWbClassScriptioContinua == c) {
    // we pass the whole text segment to the complex word breaker to find a
    // shorter answer
    AutoTArray<uint8_t, 256> breakBefore;
    breakBefore.SetLength(range.mEnd - range.mBegin);
    NS_GetComplexLineBreaks(aText + range.mBegin, range.mEnd - range.mBegin,
                            breakBefore.Elements());

    // Scan forward
    for (uint32_t i = aPos + 1; i < range.mEnd; i++) {
      if (breakBefore[i - range.mBegin]) {
        range.mEnd = i;
        break;
      }
    }

    // Scan backward
    for (uint32_t i = aPos; i > range.mBegin; i--) {
      if (breakBefore[i - range.mBegin]) {
        range.mBegin = i;
        break;
      }
    }
  }
  return range;
}

int32_t WordBreaker::Next(const char16_t* aText, uint32_t aLen, uint32_t aPos) {
  MOZ_ASSERT(aText);

  if (aPos >= aLen) {
    return NS_WORDBREAKER_NEED_MORE_TEXT;
  }

  const WordBreakClass posClass = GetClass(aText[aPos]);
  uint32_t nextBreakPos;
  for (nextBreakPos = aPos + 1; nextBreakPos < aLen; ++nextBreakPos) {
    if (posClass != GetClass(aText[nextBreakPos])) {
      break;
    }
  }

  if (kWbClassScriptioContinua == posClass) {
    // We pass the whole text segment to the complex word breaker to find a
    // shorter answer.
    const char16_t* segStart = aText + aPos;
    const uint32_t segLen = nextBreakPos - aPos + 1;
    AutoTArray<uint8_t, 256> breakBefore;
    breakBefore.SetLength(segLen);
    NS_GetComplexLineBreaks(segStart, segLen, breakBefore.Elements());

    for (uint32_t i = aPos + 1; i < nextBreakPos; ++i) {
      if (breakBefore[i - aPos]) {
        nextBreakPos = i;
        break;
      }
    }
  }

  MOZ_ASSERT(nextBreakPos != aPos);
  return nextBreakPos;
}