Class GZIPInputStream

java.util.zip.GZIPInputStream

All Implemented Interfaces:: Closeable, AutoCloseable

public class GZIPInputStream extends InflaterInputStream

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.

API Note:

The close() method should be called to release resources used by this stream, either directly, or with the try-with-resources statement.

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.

Since:

1.1

External Specifications

See Also:

Field Summary

Modifier and Type	Field	Description
`protected CRC32`	`crc`	CRC-32 for decompressed data.
`protected boolean`	`eos`	Indicates end of input stream.
`static final int`	`GZIP_MAGIC`	GZIP header magic number.

Fields declared in class InflaterInputStream

buf, inf, len

Modifier and Type	Field	Description
`protected byte[]`	`buf`	Input buffer for decompression.
`protected Inflater`	`inf`	Decompressor for this stream.
`protected int`	`len`	The total number of bytes read into the input buffer.

Fields declared in class FilterInputStream

in

Modifier and Type	Field	Description
`protected InputStream`	`in`	The input stream to be filtered.

Constructor Summary

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

Method Summary

Modifier and Type	Method	Description
`void`	`close()`	Closes this input stream and releases any system resources associated with the stream.
`int`	`read(byte[] buf, int off, int len)`	Reads decompressed data into an array of bytes, returning the number of decompressed bytes.

Methods declared in class InflaterInputStream

available, fill, mark, markSupported, read, reset, skip

Modifier and Type	Method	Description
`int`	`available()`	Returns 0 after EOF has been reached, otherwise always return 1.
`protected void`	`fill()`	Fills input buffer with more data to decompress.
`void`	`mark(int readlimit)`	Marks the current position in this input stream.
`boolean`	`markSupported()`	Tests if this input stream supports the `mark` and `reset` methods.
`int`	`read()`	Reads a byte of uncompressed data.
`void`	`reset()`	Repositions this stream to the position at the time the `mark` method was last called on this input stream.
`long`	`skip(long n)`	Skips specified number of bytes of uncompressed data.

Methods declared in class FilterInputStream

read

Modifier and Type	Method	Description
`int`	`read(byte[] b)`	Reads up to `b.length` bytes of data from this input stream into an array of bytes.

Methods declared in class InputStream

nullInputStream, readAllBytes, readNBytes, readNBytes, skipNBytes, transferTo

Modifier and Type	Method	Description
`static InputStream`	`nullInputStream()`	Returns a new `InputStream` that reads no bytes.
`byte[]`	`readAllBytes()`	Reads all remaining bytes from the input stream.
`int`	`readNBytes(byte[] b, int off, int len)`	Reads the requested number of bytes from the input stream into the given byte array.
`byte[]`	`readNBytes(int len)`	Reads up to a specified number of bytes from the input stream.
`void`	`skipNBytes(long n)`	Skips over and discards exactly `n` bytes of data from this input stream.
`long`	`transferTo(OutputStream out)`	Reads all bytes from this input stream and writes the bytes to the given output stream in the order that they are read.

Methods declared in class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Modifier and Type	Method	Description
`protected Object`	`clone()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()`	Returns a string representation of the object.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Field Details

GZIP_MAGIC

public static final int GZIP_MAGIC

GZIP header magic number.

See Also:

crc

protected CRC32 crc

CRC-32 for decompressed data.

eos

protected boolean eos

Indicates end of input stream.

Constructor Details

GZIPInputStream

public GZIPInputStream(InputStream in, int size) throws IOException

Creates a new input stream with the specified buffer size.

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

GZIPInputStream

public GZIPInputStream(InputStream in) throws IOException

Creates a new input stream with a default buffer size.

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

Method Details

read

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

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.

Overrides:

read in class InflaterInputStream

Parameters:

buf - the buffer into which the data is read

off - the start offset in the destination array buf

len - the maximum number of bytes to read into buf

Returns:

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

Throws:

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.

IOException - if the stream is closed or an I/O error has occurred.

See Also:

close

public void close() throws IOException

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

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class InflaterInputStream

Throws:

IOException - if an I/O error has occurred

See Also:

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