com.xiaomi.infra.galaxy.fds.client.model.GzipCompressingInputStream Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of galaxy-fds-sdk-java Show documentation
Xiaomi File Storage Service SDK
There is a newer version: 3.0.44
package com.xiaomi.infra.galaxy.fds.client.model;

import java.io.ByteArrayInputStream;
import java.io.FileInputStream;
import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.SequenceInputStream;
import java.util.Enumeration;
import java.util.zip.CRC32;
import java.util.zip.Deflater;
import java.util.zip.DeflaterInputStream;
import java.util.zip.DeflaterOutputStream;

public class GzipCompressingInputStream extends SequenceInputStream {
  public GzipCompressingInputStream(InputStream in) throws IOException {
    this(in, 512);
  }

  public GzipCompressingInputStream(InputStream in, int bufferSize) throws IOException {
    super(new StatefullGzipStreamEnumerator(in, bufferSize));
  }

  static enum StreamState {
    HEADER, CONTENT, TRAILER
  }

  protected static class StatefullGzipStreamEnumerator implements Enumeration {

    protected final InputStream in;
    protected final int bufferSize;
    protected StreamState state;

    public StatefullGzipStreamEnumerator(InputStream in, int bufferSize) {
      this.in = in;
      this.bufferSize = bufferSize;
      state = StreamState.HEADER;
    }

    public boolean hasMoreElements() {
      return state != null;
    }

    public InputStream nextElement() {
      switch (state) {
      case HEADER:
        state = StreamState.CONTENT;
        return createHeaderStream();
      case CONTENT:
        state = StreamState.TRAILER;
        return createContentStream();
      case TRAILER:
        state = null;
        return createTrailerStream();
      }
      return null;
    }

    static final int GZIP_MAGIC = 0x8b1f;
    static final byte[] GZIP_HEADER = new byte[] { (byte) GZIP_MAGIC,        // Magic number (short)
        (byte) (GZIP_MAGIC >> 8),  // Magic number (short)
        Deflater.DEFLATED,        // Compression method (CM)
        0,                        // Flags (FLG)
        0,                        // Modification time MTIME (int)
        0,                        // Modification time MTIME (int)
        0,                        // Modification time MTIME (int)
        0,                        // Modification time MTIME (int)
        0,                        // Extra flags (XFLG)
        0                         // Operating system (OS)
    };

    protected InputStream createHeaderStream() {
      return new ByteArrayInputStream(GZIP_HEADER);
    }

    protected InternalGzipCompressingInputStream contentStream;

    protected InputStream createContentStream() {
      contentStream = new InternalGzipCompressingInputStream(new CRC32InputStream(in), bufferSize);
      return contentStream;
    }

    protected InputStream createTrailerStream() {
      return new ByteArrayInputStream(contentStream.createTrailer());
    }
  }

  /**
   * Internal stream without header/trailer
   */
  protected static class CRC32InputStream extends FilterInputStream {
    protected CRC32 crc = new CRC32();
    protected long byteCount;

    public CRC32InputStream(InputStream in) {
      super(in);
    }

    @Override public int read() throws IOException {
      int val = super.read();
      if (val >= 0) {
        crc.update(val);
        byteCount++;
      }
      return val;
    }

    @Override public int read(byte[] b, int off, int len) throws IOException {
      len = super.read(b, off, len);
      if (len >= 0) {
        crc.update(b, off, len);
        byteCount += len;
      }
      return len;
    }

    public long getCrcValue() {
      return crc.getValue();
    }

    public long getByteCount() {
      return byteCount;
    }
  }

  /**
   * Internal stream without header/trailer
   */
  protected static class InternalGzipCompressingInputStream extends DeflaterInputStream {
    protected final CRC32InputStream crcIn;

    public InternalGzipCompressingInputStream(CRC32InputStream in, int bufferSize) {
      super(in, new Deflater(Deflater.DEFAULT_COMPRESSION, true), bufferSize);
      crcIn = in;
    }

    public void close() throws IOException {
      if (in != null) {
        try {
          def.end();
          in.close();
        } finally {
          in = null;
        }
      }
    }

    protected final static int TRAILER_SIZE = 8;

    public byte[] createTrailer() {
      byte[] trailer = new byte[TRAILER_SIZE];
      writeTrailer(trailer, 0);
      return trailer;
    }

    /*
     * Writes GZIP member trailer to a byte array, starting at a given
     * offset.
     */
    private void writeTrailer(byte[] buf, int offset) {
      writeInt((int) crcIn.getCrcValue(), buf, offset); // CRC-32 of uncompr. data
      writeInt((int) crcIn.getByteCount(), buf, offset + 4); // Number of uncompr. bytes
    }

    /*
     * Writes integer in Intel byte order to a byte array, starting at a
     * given offset.
     */
    private void writeInt(int i, byte[] buf, int offset) {
      writeShort(i & 0xffff, buf, offset);
      writeShort((i >> 16) & 0xffff, buf, offset + 2);
    }

    /*
     * Writes short integer in Intel byte order to a byte array, starting
     * at a given offset
     */
    private void writeShort(int s, byte[] buf, int offset) {
      buf[offset] = (byte) (s & 0xff);
      buf[offset + 1] = (byte) ((s >> 8) & 0xff);
    }
  }

}