Пример #1
0
  /*
   * gets an (uncompressed) stream representing the chunk data returns null if
   * the chunk is not found or an error occurs
   */
  public synchronized DataInputStream getChunkDataInputStream(int x, int z) {
    if (outOfBounds(x, z)) {
      debugln("READ", x, z, "out of bounds");
      return null;
    }

    try {
      int offset = getOffset(x, z);
      if (offset == 0) {
        // debugln("READ", x, z, "miss");
        return null;
      }

      int sectorNumber = offset >> 8;
      int numSectors = offset & 0xFF;

      if (sectorNumber + numSectors > sectorFree.size()) {
        debugln("READ", x, z, "invalid sector");
        return null;
      }

      file.seek(sectorNumber * SECTOR_BYTES);
      int length = file.readInt();

      if (length > SECTOR_BYTES * numSectors) {
        debugln("READ", x, z, "invalid length: " + length + " > 4096 * " + numSectors);
        return null;
      }

      byte version = file.readByte();
      if (version == VERSION_GZIP) {
        byte[] data = new byte[length - 1];
        file.read(data);
        DataInputStream ret =
            new DataInputStream(
                new BufferedInputStream(new GZIPInputStream(new ByteArrayInputStream(data))));
        // debug("READ", x, z, " = found");
        return ret;
      } else if (version == VERSION_DEFLATE) {
        byte[] data = new byte[length - 1];
        file.read(data);
        DataInputStream ret =
            new DataInputStream(
                new BufferedInputStream(new InflaterInputStream(new ByteArrayInputStream(data))));
        // debug("READ", x, z, " = found");
        return ret;
      }

      debugln("READ", x, z, "unknown version " + version);
      return null;
    } catch (IOException e) {
      debugln("READ", x, z, "exception");
      return null;
    }
  }
Пример #2
0
  public static long checksumRandomAccessFile(Path filename) throws IOException {
    try (RandomAccessFile file = new RandomAccessFile(filename.toFile(), "r")) {
      long length = file.length();
      CRC32 crc = new CRC32();

      for (long p = 0; p < length; p++) {
        file.seek(p);
        int c = file.readByte();
        crc.update(c);
      }
      return crc.getValue();
    }
  }