content: /*
   * 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.
   */
  
  package com.taobao.atlas.dex;
  
  import com.taobao.atlas.dex.util.ByteInput;
  
  import java.io.UTFDataFormatException;
  
  /**
   * Modified UTF-8 as described in the dex file format spec.
   *
   * <p>Derived from libcore's MUTF-8 encoder at java.nio.charset.ModifiedUtf8.
   */
  public final class Mutf8 {
      private Mutf8() {}
  
      /**
       * Decodes bytes from {@code in} into {@code out} until a delimiter 0x00 is
       * encountered. Returns a new string containing the decoded characters.
       */
      public static String decode(ByteInput in, char[] out) throws UTFDataFormatException {
          int s = 0;
          while (true) {
              char a = (char) (in.readByte() & 0xff);
              if (a == 0) {
                  return new String(out, 0, s);
              }
              out[s] = a;
              if (a < '\u0080') {
                  s++;
              } else if ((a & 0xe0) == 0xc0) {
                  int b = in.readByte() & 0xff;
                  if ((b & 0xC0) != 0x80) {
                      throw new UTFDataFormatException("bad second byte");
                  }
                  out[s++] = (char) (((a & 0x1F) << 6) | (b & 0x3F));
              } else if ((a & 0xf0) == 0xe0) {
                  int b = in.readByte() & 0xff;
                  int c = in.readByte() & 0xff;
                  if (((b & 0xC0) != 0x80) || ((c & 0xC0) != 0x80)) {
                      throw new UTFDataFormatException("bad second or third byte");
                  }
                  out[s++] = (char) (((a & 0x0F) << 12) | ((b & 0x3F) << 6) | (c & 0x3F));
              } else {
                  throw new UTFDataFormatException("bad byte");
              }
          }
      }
  
      /**
       * Returns the number of bytes the modified UTF8 representation of 's' would take.
       */
      private static long countBytes(String s, boolean shortLength) throws UTFDataFormatException {
          long result = 0;
          final int length = s.length();
          for (int i = 0; i < length; ++i) {
              char ch = s.charAt(i);
              if (ch != 0 && ch <= 127) { // U+0000 uses two bytes.
                  ++result;
              } else if (ch <= 2047) {
                  result += 2;
              } else {
                  result += 3;
              }
              if (shortLength && result > 65535) {
                  throw new UTFDataFormatException("String more than 65535 UTF bytes long");
              }
          }
          return result;
      }
  
      /**
       * Encodes the modified UTF-8 bytes corresponding to {@code s} into  {@code
       * dst}, starting at {@code offset}.
       */
      public static void encode(byte[] dst, int offset, String s) {
          final int length = s.length();
          for (int i = 0; i < length; i++) {
              char ch = s.charAt(i);
              if (ch != 0 && ch <= 127) { // U+0000 uses two bytes.
                  dst[offset++] = (byte) ch;
              } else if (ch <= 2047) {
                  dst[offset++] = (byte) (0xc0 | (0x1f & (ch >> 6)));
                  dst[offset++] = (byte) (0x80 | (0x3f & ch));
              } else {
                  dst[offset++] = (byte) (0xe0 | (0x0f & (ch >> 12)));
                  dst[offset++] = (byte) (0x80 | (0x3f & (ch >> 6)));
                  dst[offset++] = (byte) (0x80 | (0x3f & ch));
              }
          }
      }
  
      /**
       * Returns an array containing the <i>modified UTF-8</i> form of {@code s}.
       */
      public static byte[] encode(String s) throws UTFDataFormatException {
          int utfCount = (int) countBytes(s, true);
          byte[] result = new byte[utfCount];
          encode(result, 0, s);
          return result;
      }
  }
  