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word_iterator.cc

// Copyright (c) 2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/i18n/word_iterator.h"

#include "base/logging.h"
#include "unicode/ubrk.h"
#include "unicode/ustring.h"

const size_t npos = -1;

WordIterator::WordIterator(const std::wstring& str, BreakType break_type)
    : iter_(NULL),
      string_(str),
      break_type_(break_type),
      prev_(npos),
      pos_(0) {
}

WordIterator::~WordIterator() {
  if (iter_)
    ubrk_close(iter_);
}

bool WordIterator::Init() {
  UErrorCode status = U_ZERO_ERROR;
  UBreakIteratorType break_type;
  switch (break_type_) {
    case BREAK_WORD:
      break_type = UBRK_WORD;
      break;
    case BREAK_LINE:
      break_type = UBRK_LINE;
      break;
    default:
      NOTREACHED();
      break_type = UBRK_LINE;
  }
#if defined(WCHAR_T_IS_UTF16)
  iter_ = ubrk_open(break_type, NULL,
                    string_.data(), static_cast<int32_t>(string_.size()),
                    &status);
#else  // WCHAR_T_IS_UTF16
  // When wchar_t is wider than UChar (16 bits), transform |string_| into a
  // UChar* string.  Size the UChar* buffer to be large enough to hold twice
  // as many UTF-16 code points as there are UCS-4 characters, in case each
  // character translates to a UTF-16 surrogate pair, and leave room for a NUL
  // terminator.
  // TODO(avi): avoid this alloc
  chars_.resize(string_.length() * sizeof(UChar) + 1);

  UErrorCode error = U_ZERO_ERROR;
  int32_t destLength;
  u_strFromWCS(&chars_[0], chars_.size(), &destLength, string_.data(),
               string_.length(), &error);

  iter_ = ubrk_open(break_type, NULL, &chars_[0], destLength, &status);
#endif
  if (U_FAILURE(status)) {
    NOTREACHED() << "ubrk_open failed";
    return false;
  }
  ubrk_first(iter_);  // Move the iterator to the beginning of the string.
  return true;
}

bool WordIterator::Advance() {
  prev_ = pos_;
  const int32_t pos = ubrk_next(iter_);
  if (pos == UBRK_DONE) {
    pos_ = npos;
    return false;
  } else {
    pos_ = static_cast<size_t>(pos);
    return true;
  }
}

bool WordIterator::IsWord() const {
  return (ubrk_getRuleStatus(iter_) != UBRK_WORD_NONE);
}

std::wstring WordIterator::GetWord() const {
  DCHECK(prev_ != npos && pos_ != npos);
#if defined(WCHAR_T_IS_UTF16)
  return string_.substr(prev_, pos_ - prev_);
#else  // WCHAR_T_IS_UTF16
  // See comment in Init().  If there are no surrogate pairs,
  // |out_length| will be exactly |in_length|, if there are surrogate
  // pairs it will be less than |in_length|.
  int32_t out_length;
  UErrorCode error = U_ZERO_ERROR;
  const int32_t in_length = pos_ - prev_;
  std::vector<std::wstring::value_type> out_buffer(in_length);
  u_strToWCS(&out_buffer[0], in_length, &out_length,
             &chars_[prev_], in_length, &error);
  DCHECK_LE(out_length, in_length);
  return std::wstring(&out_buffer[0], out_length);
#endif
}

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