File	Doc	Category	Size	Date	Package
GZIPInputStream.java	API Doc	Java SE 6 API	6537	Tue Jun 10 00:26:00 BST 2008	java.util.zip

GZIPInputStream

• java.lang.Object
  • java.io.InputStream
    • java.io.FilterInputStream
      • java.util.zip.InflaterInputStream

Fields Summary
protected CRC32	crc CRC-32 for uncompressed data.
protected boolean	eos Indicates end of input stream.
private boolean	closed
public static final int	GZIP_MAGIC GZIP header magic number.
private static final int	FTEXT
private static final int	FHCRC
private static final int	FEXTRA
private static final int	FNAME
private static final int	FCOMMENT
private byte[]	tmpbuf

Constructors Summary
public GZIPInputStream(InputStream in, int size) Creates a new input stream with the specified buffer size. param in the input stream param size the input buffer size exception IOException if an I/O error has occurred exception IllegalArgumentException if size is <= 0 super(in, new Inflater(true), size); usesDefaultInflater = true; readHeader(); crc.reset();
public GZIPInputStream(InputStream in) Creates a new input stream with a default buffer size. param in the input stream exception IOException if an I/O error has occurred this(in, 512);

Methods Summary
public void	close() Closes this input stream and releases any system resources associated with the stream. exception IOException if an I/O error has occurred if (!closed) { super.close(); eos = true; closed = true; }
private void	ensureOpen() Check to make sure that this stream has not been closed if (closed) { throw new IOException("Stream closed"); }
public int	read(byte[] buf, int off, int len) Reads uncompressed data into an array of bytes. If len is not zero, the method will block until some input can be decompressed; otherwise, no bytes are read and 0 is returned. param buf the buffer into which the data is read param off the start offset in the destination array b param len the maximum number of bytes read return the actual number of bytes read, or -1 if the end of the compressed input stream is reached exception NullPointerException If buf is null. exception IndexOutOfBoundsException If off is negative, len is negative, or len is greater than buf.length - off exception IOException if an I/O error has occurred or the compressed input data is corrupt ensureOpen(); if (eos) { return -1; } len = super.read(buf, off, len); if (len == -1) { readTrailer(); eos = true; } else { crc.update(buf, off, len); } return len;
private void	readHeader() // File comment /* * Reads GZIP member header. */ CheckedInputStream in = new CheckedInputStream(this.in, crc); crc.reset(); // Check header magic if (readUShort(in) != GZIP_MAGIC) { throw new IOException("Not in GZIP format"); } // Check compression method if (readUByte(in) != 8) { throw new IOException("Unsupported compression method"); } // Read flags int flg = readUByte(in); // Skip MTIME, XFL, and OS fields skipBytes(in, 6); // Skip optional extra field if ((flg & FEXTRA) == FEXTRA) { skipBytes(in, readUShort(in)); } // Skip optional file name if ((flg & FNAME) == FNAME) { while (readUByte(in) != 0) ; } // Skip optional file comment if ((flg & FCOMMENT) == FCOMMENT) { while (readUByte(in) != 0) ; } // Check optional header CRC if ((flg & FHCRC) == FHCRC) { int v = (int)crc.getValue() & 0xffff; if (readUShort(in) != v) { throw new IOException("Corrupt GZIP header"); } }
private void	readTrailer() InputStream in = this.in; int n = inf.getRemaining(); if (n > 0) { in = new SequenceInputStream( new ByteArrayInputStream(buf, len - n, n), in); } // Uses left-to-right evaluation order if ((readUInt(in) != crc.getValue()) || // rfc1952; ISIZE is the input size modulo 2^32 (readUInt(in) != (inf.getBytesWritten() & 0xffffffffL))) throw new IOException("Corrupt GZIP trailer");
private int	readUByte(java.io.InputStream in) int b = in.read(); if (b == -1) { throw new EOFException(); } if (b < -1 || b > 255) { // Report on this.in, not argument in; see read{Header, Trailer}. throw new IOException(this.in.getClass().getName() + ".read() returned value out of range -1..255: " + b); } return b;
private long	readUInt(java.io.InputStream in) long s = readUShort(in); return ((long)readUShort(in) << 16) | s;
private int	readUShort(java.io.InputStream in) int b = readUByte(in); return ((int)readUByte(in) << 8) | b;
private void	skipBytes(java.io.InputStream in, int n) /* * Skips bytes of input data blocking until all bytes are skipped. * Does not assume that the input stream is capable of seeking. */ while (n > 0) { int len = in.read(tmpbuf, 0, n < tmpbuf.length ? n : tmpbuf.length); if (len == -1) { throw new EOFException(); } n -= len; }