OpenJDK 27 · java.util.zip.GZIPInputStream · APIdia, the JavaDoc alternative

This class implements a stream filter for decompressing GZIP file format data.

GZIP file format

The GZIP file format is specified by RFC 1952. The format, as specified in section 2.2 of the RFC, consists of a series of "members" that appear one after another in the stream with no additional information before, between, or after them. Each member consists of a header, followed by data that is compressed using the deflate algorithm, and then a trailer.

This class is capable of reading a stream consisting of a series of members.

Reading from the stream may read and buffer bytes from the underlying stream. This includes bytes that follow a member's trailer. Whether or not any additional bytes have been read past a member's trailer, the read methods on this class yield decompressed data from at most one member; data from multiple members is not combined in a single read operation.

Thread safety

GZIPInputStream is not safe for use by multiple concurrent threads. Any multithreaded concurrent use must be guarded by appropriate synchronization.

Implementation Note

After reading a member trailer, the read method calls InputStream#available() on the underlying stream to determine whether additional bytes are available that may represent a subsequent member. If the jdk.util.gzip.tryReadAheadAfterTrailer system property is set to true, then the call to InputStream.available() is skipped and the implementation instead attempts to read a subsequent member in the stream. GZIPInputStream depends on the return value of InputStream.available() to reliably process a stream with a series of members. Consequently, it may be necessary to set this property in environments that process streams with a series of members. By default, the jdk.util.gzip.tryReadAheadAfterTrailer system property is not set, and InputStream.available() gets called.

Field Summary

Modifier and Type	Field and Description
private static final boolean	alwaysReadNextMember
private boolean	closed Hides java.util.zip.InflaterInputStream.closed.
protected CRC32	crc CRC-32 for decompressed data.
protected boolean	eos Indicates end of input stream.
private static final int	FCOMMENT
private static final int	FEXTRA
private static final int	FHCRC
private static final int	FNAME
public static final int	GZIP_MAGIC GZIP header magic number.
private final byte[]	tmpbuf

Inherited from java.util.zip.InflaterInputStream:: buf inf len usesDefaultInflater

Constructor Summary

Access	Constructor and Description
public	GZIPInputStream(InputStream the input stream in, int the input buffer size size) Creates a new input stream with the specified buffer size.
public	GZIPInputStream(InputStream the input stream in) Creates a new input stream with a default buffer size.

Method Summary

Modifier and Type	Method and Description
private void	checkUnexpectedByte(final int b)
public void	close() Overrides java.util.zip.InflaterInputStream.close. Implements java.io.Closeable.close. Closes this input stream and releases any system resources associated with the stream.
private static Inflater	createInflater(InputStream in, int size)
private void	ensureOpen() Hides java.util.zip.InflaterInputStream.ensureOpen. Check to make sure that this stream has not been closed
private boolean	hasNoMoreMembers() Reads the current GZIP member's trailer and returns true if the end-of-stream is reached.
public int	Returns: the actual number of bytes decompressed from a GZIP member, or -1 if the end-of-stream is reached read(byte[] the buffer into which the data is read buf, int the start offset in the destination array `buf` off, int the maximum number of bytes to read into `buf` len) Overrides java.util.zip.InflaterInputStream.read. Reads decompressed data into an array of bytes, returning the number of decompressed bytes.
private int	readHeader(InputStream stream, boolean failOnEOF)
private void	readTrailer(final InputStream the InputStream containing the trailer stream) Reads the current member's trailer
private int	readUByte(InputStream in)
private long	readUInt(InputStream in)
private int	readUShort(InputStream in)
private void	skipBytes(InputStream in, int n)

Inherited from java.util.zip.InflaterInputStream:: available fill mark markSupported read reset skip

Field Detail

alwaysReadNextMember	back to summary
private static final boolean alwaysReadNextMember

closed	back to summary
private boolean closed Hides java.util.zip.InflaterInputStream.closed.

crc	back to summary
protected CRC32 crc CRC-32 for decompressed data.

eos	back to summary
protected boolean eos Indicates end of input stream.

FCOMMENT	back to summary
private static final int FCOMMENT

FEXTRA	back to summary
private static final int FEXTRA

FHCRC	back to summary
private static final int FHCRC

FNAME	back to summary
private static final int FNAME

GZIP_MAGIC	back to summary
public static final int GZIP_MAGIC GZIP header magic number.

tmpbuf	back to summary
private final byte[] tmpbuf

Constructor Detail

GZIPInputStream back to summary

GZIPInputStream	back to summary
public GZIPInputStream(InputStream in, int size) throws IOException Creates a new input stream with the specified buffer size. Parameters in:InputStream the input stream size:int the input buffer size Exceptions IOException: if an I/O error occurs when reading the member header from the underlying stream ZipException: if a GZIP format error has occurred or the compression method used is unsupported NullPointerException: if `in` is null IllegalArgumentException: if `size <= 0`

public GZIPInputStream(InputStream in, int size) throws IOException

Creates a new input stream with the specified buffer size.

Parameters

in:InputStream: the input stream
size:int: the input buffer size

Exceptions

IOException:: if an I/O error occurs when reading the member header from the underlying stream
ZipException:: if a GZIP format error has occurred or the compression method used is unsupported
NullPointerException:: if in is null
IllegalArgumentException:: if size <= 0

GZIPInputStream back to summary

GZIPInputStream	back to summary
public GZIPInputStream(InputStream in) throws IOException Creates a new input stream with a default buffer size. Parameters in:InputStream the input stream Exceptions IOException: if an I/O error occurs when reading the member header from the underlying stream ZipException: if a GZIP format error has occurred or the compression method used is unsupported NullPointerException: if `in` is null

public GZIPInputStream(InputStream in) throws IOException

Creates a new input stream with a default buffer size.

Parameters

in:InputStream: the input stream

Exceptions

IOException:: if an I/O error occurs when reading the member header from the underlying stream
ZipException:: if a GZIP format error has occurred or the compression method used is unsupported
NullPointerException:: if in is null

Method Detail

checkUnexpectedByte	back to summary
private void checkUnexpectedByte(final int b) throws IOException

close	back to summary
public void close() throws IOException Overrides java.util.zip.InflaterInputStream.close. Implements java.io.Closeable.close. Closes this input stream and releases any system resources associated with the stream. Annotations @Override Exceptions IOException: if an I/O error has occurred

back to summary

public void close() throws IOException

Overrides java.util.zip.InflaterInputStream.close.

Implements java.io.Closeable.close.

Closes this input stream and releases any system resources associated with the stream.

Annotations

@Override

Exceptions

IOException:: if an I/O error has occurred

createInflater	back to summary
private static Inflater createInflater(InputStream in, int size)

ensureOpen	back to summary
private void ensureOpen() throws IOException Hides java.util.zip.InflaterInputStream.ensureOpen. Check to make sure that this stream has not been closed

ensureOpen

back to summary

private void ensureOpen() throws IOException

Hides java.util.zip.InflaterInputStream.ensureOpen.

Check to make sure that this stream has not been closed

hasNoMoreMembers	back to summary
private boolean hasNoMoreMembers() throws IOException Reads the current GZIP member's trailer and returns true if the end-of-stream is reached. After reading the current member's trailer, if the stream has a subsequent GZIP member, then this method reads that member's header and returns false indicating that there is another member in the stream.

read back to summary

read	back to summary
public int read(byte[] buf, int off, int len) throws IOException Overrides java.util.zip.InflaterInputStream.read. Reads decompressed data into an array of bytes, returning the number of decompressed 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. If this method returns a nonzero integer n then `buf[off]` through `buf[off+`n`-1]` contain the decompressed data. The content of elements `buf[off+`n`]` through `buf[off+`len`-1]` is undefined, contrary to the specification of the `InputStream` superclass, so an implementation is free to modify these elements during the inflate operation. If this method returns `-1` or throws an exception then the content of `buf[off]` through `buf[off+`len`-1]` is undefined. Parameters buf:byte[] the buffer into which the data is read off:int the start offset in the destination array `buf` len:int the maximum number of bytes to read into `buf` Returns:int the actual number of bytes decompressed from a GZIP member, or -1 if the end-of-stream is reached Annotations @Override Exceptions IOException: if the stream is closed or an I/O error has occurred. NullPointerException: If `buf` is `null`. IndexOutOfBoundsException: If `off` is negative, `len` is negative, or `len` is greater than `buf.length - off` ZipException: if the compressed input data is corrupt. See Also `GZIP file format`

public int read(byte[] buf, int off, int len) throws IOException

Overrides java.util.zip.InflaterInputStream.read.

Reads decompressed data into an array of bytes, returning the number of decompressed 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.

If this method returns a nonzero integer n then buf[off] through buf[off+n-1] contain the decompressed data. The content of elements buf[off+n] through buf[off+len-1] is undefined, contrary to the specification of the InputStream superclass, so an implementation is free to modify these elements during the inflate operation. If this method returns -1 or throws an exception then the content of buf[off] through buf[off+len-1] is undefined.

Parameters

buf:byte[]: the buffer into which the data is read
off:int: the start offset in the destination array buf
len:int: the maximum number of bytes to read into buf

Returns:int

the actual number of bytes decompressed from a GZIP member, or -1 if the end-of-stream is reached

Annotations

@Override

Exceptions

IOException:: if the stream is closed or an I/O error has occurred.
NullPointerException:: If buf is null.
IndexOutOfBoundsException:: If off is negative, len is negative, or len is greater than buf.length - off
ZipException:: if the compressed input data is corrupt.

See Also

GZIP file format

readHeader	back to summary
private int readHeader(InputStream stream, boolean failOnEOF) throws IOException

readTrailer	back to summary
private void readTrailer(final InputStream stream) throws IOException Reads the current member's trailer Parameters stream:InputStream the InputStream containing the trailer

readTrailer

back to summary

private void readTrailer(final InputStream stream) throws IOException

Reads the current member's trailer

Parameters

stream:InputStream: the InputStream containing the trailer

readUByte	back to summary
private int readUByte(InputStream in) throws IOException

readUInt	back to summary
private long readUInt(InputStream in) throws IOException

readUShort	back to summary
private int readUShort(InputStream in) throws IOException

skipBytes	back to summary
private void skipBytes(InputStream in, int n) throws IOException

public Class GZIPInputStream

GZIP file format

Thread safety

Field Summary

Constructor Summary

Method Summary

Field Detail

Constructor Detail

Method Detail