libdexfile/dex/utf-inl.h

/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef ART_LIBDEXFILE_DEX_UTF_INL_H_
#define ART_LIBDEXFILE_DEX_UTF_INL_H_

#include "utf.h"

namespace art {

inline uint16_t GetTrailingUtf16Char(uint32_t maybe_pair) {
  return static_cast<uint16_t>(maybe_pair >> 16);
}

inline uint16_t GetLeadingUtf16Char(uint32_t maybe_pair) {
  return static_cast<uint16_t>(maybe_pair & 0x0000FFFF);
}

inline uint32_t GetUtf16FromUtf8(const char** utf8_data_in) {
  const uint8_t one = *(*utf8_data_in)++;
  if ((one & 0x80) == 0) {
    // one-byte encoding
    return one;
  }

  const uint8_t two = *(*utf8_data_in)++;
  if ((one & 0x20) == 0) {
    // two-byte encoding
    return ((one & 0x1f) << 6) | (two & 0x3f);
  }

  const uint8_t three = *(*utf8_data_in)++;
  if ((one & 0x10) == 0) {
    return ((one & 0x0f) << 12) | ((two & 0x3f) << 6) | (three & 0x3f);
  }

  // Four byte encodings need special handling. We'll have
  // to convert them into a surrogate pair.
  const uint8_t four = *(*utf8_data_in)++;

  // Since this is a 4 byte UTF-8 sequence, it will lie between
  // U+10000 and U+1FFFFF.
  //
  // TODO: What do we do about values in (U+10FFFF, U+1FFFFF) ? The
  // spec says they're invalid but nobody appears to check for them.
  const uint32_t code_point = ((one & 0x0f) << 18) | ((two & 0x3f) << 12)
      | ((three & 0x3f) << 6) | (four & 0x3f);

  uint32_t surrogate_pair = 0;
  // Step two: Write out the high (leading) surrogate to the bottom 16 bits
  // of the of the 32 bit type.
  surrogate_pair |= ((code_point >> 10) + 0xd7c0) & 0xffff;
  // Step three : Write out the low (trailing) surrogate to the top 16 bits.
  surrogate_pair |= ((code_point & 0x03ff) + 0xdc00) << 16;

  return surrogate_pair;
}

inline int CompareModifiedUtf8ToModifiedUtf8AsUtf16CodePointValues(const char* utf8_1,
                                                                   const char* utf8_2) {
  uint32_t c1, c2;
  do {
    c1 = *utf8_1;
    c2 = *utf8_2;
    // Did we reach a terminating character?
    if (c1 == 0) {
      return (c2 == 0) ? 0 : -1;
    } else if (c2 == 0) {
      return 1;
    }

    c1 = GetUtf16FromUtf8(&utf8_1);
    c2 = GetUtf16FromUtf8(&utf8_2);
  } while (c1 == c2);

  const uint32_t leading_surrogate_diff = GetLeadingUtf16Char(c1) - GetLeadingUtf16Char(c2);
  if (leading_surrogate_diff != 0) {
      return static_cast<int>(leading_surrogate_diff);
  }

  return GetTrailingUtf16Char(c1) - GetTrailingUtf16Char(c2);
}

template <bool kUseShortZero, bool kUse4ByteSequence, bool kReplaceBadSurrogates, typename Append>
inline void ConvertUtf16ToUtf8(const uint16_t* utf16, size_t char_count, Append&& append) {
  static_assert(kUse4ByteSequence || !kReplaceBadSurrogates);

  // Use local helpers instead of macros from `libicu` to avoid the dependency on `libicu`.
  auto is_lead = [](uint16_t ch) ALWAYS_INLINE { return (ch & 0xfc00u) == 0xd800u; };
  auto is_trail = [](uint16_t ch) ALWAYS_INLINE { return (ch & 0xfc00u) == 0xdc00u; };
  auto is_surrogate = [](uint16_t ch) ALWAYS_INLINE { return (ch & 0xf800u) == 0xd800u; };
  auto is_surrogate_lead = [](uint16_t ch) ALWAYS_INLINE { return (ch & 0x0400u) == 0u; };
  auto get_supplementary = [](uint16_t lead, uint16_t trail) ALWAYS_INLINE {
    constexpr uint32_t offset = (0xd800u << 10) + 0xdc00u - 0x10000u;
    return (static_cast<uint32_t>(lead) << 10) + static_cast<uint32_t>(trail) - offset;
  };

  for (size_t i = 0u; i < char_count; ++i) {
    auto has_trail = [&]() { return i + 1u != char_count && is_trail(utf16[i + 1u]); };

    uint16_t ch = utf16[i];
    if (ch < 0x80u && (kUseShortZero || ch != 0u)) {
      // One byte.
      append(ch);
    } else if (ch < 0x800u) {
      // Two bytes.
      append((ch >> 6) | 0xc0);
      append((ch & 0x3f) | 0x80);
    } else if (kReplaceBadSurrogates
                   ? is_surrogate(ch)
                   : kUse4ByteSequence && is_lead(ch) && has_trail()) {
      if (kReplaceBadSurrogates && (!is_surrogate_lead(ch) || !has_trail())) {
        append('?');
      } else {
        // We have a *valid* surrogate pair.
        uint32_t code_point = get_supplementary(ch, utf16[i + 1u]);
        ++i;  //  Consume the leading surrogate.
        // Four bytes.
        append((code_point >> 18) | 0xf0);
        append(((code_point >> 12) & 0x3f) | 0x80);
        append(((code_point >> 6) & 0x3f) | 0x80);
        append((code_point & 0x3f) | 0x80);
      }
    } else {
      // Three bytes.
      append((ch >> 12) | 0xe0);
      append(((ch >> 6) & 0x3f) | 0x80);
      append((ch & 0x3f) | 0x80);
    }
  }
}

}  // namespace art

#endif  // ART_LIBDEXFILE_DEX_UTF_INL_H_