import org.apache.hadoop.io.compress.bzip2.Bzip2Decompressor; //导入依赖的package包/类
@Test
public void testCompressDecompress() {
  byte[] rawData = null;
  int rawDataSize = 0;
  rawDataSize = 1024 * 64;
  rawData = generate(rawDataSize);
  try {
    Bzip2Compressor compressor = new Bzip2Compressor();
    Bzip2Decompressor decompressor = new Bzip2Decompressor();
    assertFalse("testBzip2CompressDecompress finished error",
        compressor.finished());
    compressor.setInput(rawData, 0, rawData.length);
    assertTrue("testBzip2CompressDecompress getBytesRead before error",
        compressor.getBytesRead() == 0);
    compressor.finish();

    byte[] compressedResult = new byte[rawDataSize];
    int cSize = compressor.compress(compressedResult, 0, rawDataSize);
    assertTrue("testBzip2CompressDecompress getBytesRead after error",
        compressor.getBytesRead() == rawDataSize);
    assertTrue(
        "testBzip2CompressDecompress compressed size no less than original size",
        cSize < rawDataSize);
    decompressor.setInput(compressedResult, 0, cSize);
    byte[] decompressedBytes = new byte[rawDataSize];
    decompressor.decompress(decompressedBytes, 0, decompressedBytes.length);
    assertArrayEquals("testBzip2CompressDecompress arrays not equals ",
        rawData, decompressedBytes);
    compressor.reset();
    decompressor.reset();
  } catch (IOException ex) {
    fail("testBzip2CompressDecompress ex !!!" + ex);
  }
}
 

import org.apache.hadoop.io.compress.bzip2.Bzip2Decompressor; //导入依赖的package包/类
/**
 * Check if native-bzip2 code is loaded & initialized correctly and 
 * can be loaded for this job.
 * 
 * @param conf configuration
 * @return <code>true</code> if native-bzip2 is loaded & initialized 
 *         and can be loaded for this job, else <code>false</code>
 */
public static boolean isNativeBzip2Loaded(Configuration conf) {
  String libname = conf.get("io.compression.codec.bzip2.library", 
                            "system-native");
  if (!bzip2LibraryName.equals(libname)) {
    nativeBzip2Loaded = false;
    bzip2LibraryName = libname;
    if (libname.equals("java-builtin")) {
      LOG.info("Using pure-Java version of bzip2 library");
    } else if (conf.getBoolean(
              CommonConfigurationKeys.IO_NATIVE_LIB_AVAILABLE_KEY, 
              CommonConfigurationKeys.IO_NATIVE_LIB_AVAILABLE_DEFAULT) &&
        NativeCodeLoader.isNativeCodeLoaded()) {
      try {
        // Initialize the native library.
        Bzip2Compressor.initSymbols(libname);
        Bzip2Decompressor.initSymbols(libname);
        nativeBzip2Loaded = true;
        LOG.info("Successfully loaded & initialized native-bzip2 library " +
                 libname);
      } catch (Throwable t) {
        LOG.warn("Failed to load/initialize native-bzip2 library " + 
                 libname + ", will use pure-Java version");
      }
    }
  }
  return nativeBzip2Loaded;
}
 

import org.apache.hadoop.io.compress.bzip2.Bzip2Decompressor; //导入依赖的package包/类
/**
 * Check if native-bzip2 code is loaded & initialized correctly and 
 * can be loaded for this job.
 * 
 * @param conf configuration
 * @return <code>true</code> if native-bzip2 is loaded & initialized 
 *         and can be loaded for this job, else <code>false</code>
 */
public static synchronized boolean isNativeBzip2Loaded(Configuration conf) {
  String libname = conf.get("io.compression.codec.bzip2.library", 
                            "system-native");
  if (!bzip2LibraryName.equals(libname)) {
    nativeBzip2Loaded = false;
    bzip2LibraryName = libname;
    if (libname.equals("java-builtin")) {
      LOG.info("Using pure-Java version of bzip2 library");
    } else if (conf.getBoolean(
              CommonConfigurationKeys.IO_NATIVE_LIB_AVAILABLE_KEY, 
              CommonConfigurationKeys.IO_NATIVE_LIB_AVAILABLE_DEFAULT) &&
        NativeCodeLoader.isNativeCodeLoaded()) {
      try {
        // Initialize the native library.
        Bzip2Compressor.initSymbols(libname);
        Bzip2Decompressor.initSymbols(libname);
        nativeBzip2Loaded = true;
        LOG.info("Successfully loaded & initialized native-bzip2 library " +
                 libname);
      } catch (Throwable t) {
        LOG.warn("Failed to load/initialize native-bzip2 library " + 
                 libname + ", will use pure-Java version");
      }
    }
  }
  return nativeBzip2Loaded;
}
 

import org.apache.hadoop.io.compress.bzip2.Bzip2Decompressor; //导入依赖的package包/类
/**
 * Return the appropriate type of the bzip2 decompressor. 
 * 
 * @param conf configuration
 * @return the appropriate type of the bzip2 decompressor.
 */
public static Class<? extends Decompressor> 
getBzip2DecompressorType(Configuration conf) {
  return  isNativeBzip2Loaded(conf) ? 
    Bzip2Decompressor.class : BZip2DummyDecompressor.class;
}
 

import org.apache.hadoop.io.compress.bzip2.Bzip2Decompressor; //导入依赖的package包/类
/**
 * Return the appropriate implementation of the bzip2 decompressor. 
 * 
 * @param conf configuration
 * @return the appropriate implementation of the bzip2 decompressor.
 */
public static Decompressor getBzip2Decompressor(Configuration conf) {
  return isNativeBzip2Loaded(conf) ? 
    new Bzip2Decompressor() : new BZip2DummyDecompressor();
}