com.google.common.io

Class ByteSource

java.lang.Object

com.google.common.io.ByteSource

public abstract class ByteSource
extends Object

A readable source of bytes, such as a file. Unlike an InputStream, a ByteSource is not an open, stateful stream for input that can be read and closed. Instead, it is an immutable supplier of InputStream instances.

ByteSource provides two kinds of methods:

• Methods that return a stream: These methods should return a new, independent instance each time they are called. The caller is responsible for ensuring that the returned stream is closed.
• Convenience methods: These are implementations of common operations that are typically implemented by opening a stream using one of the methods in the first category, doing something and finally closing the stream that was opened.

Since:

14.0

Author:

Colin Decker

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ByteSource() Constructor for use by subclasses.

Method Summary

Methods

Modifier and Type	Method and Description
CharSource	asCharSource(Charset charset) Returns a CharSource view of this byte source that decodes bytes read from this source as characters using the given Charset.
static ByteSource	concat(ByteSource... sources) Concatenates multiple ByteSource instances into a single source.
static ByteSource	concat(Iterable<? extends ByteSource> sources) Concatenates multiple ByteSource instances into a single source.
static ByteSource	concat(Iterator<? extends ByteSource> sources) Concatenates multiple ByteSource instances into a single source.
boolean	contentEquals(ByteSource other) Checks that the contents of this byte source are equal to the contents of the given byte source.
long	copyTo(ByteSink sink) Copies the contents of this byte source to the given ByteSink.
long	copyTo(OutputStream output) Copies the contents of this byte source to the given OutputStream.
static ByteSource	empty() Returns an immutable ByteSource that contains no bytes.
HashCode	hash(HashFunction hashFunction) Hashes the contents of this byte source using the given hash function.
boolean	isEmpty() Returns whether the source has zero bytes.
InputStream	openBufferedStream() Opens a new buffered InputStream for reading from this source.
abstract InputStream	openStream() Opens a new InputStream for reading from this source.
byte[]	read() Reads the full contents of this byte source as a byte array.
<T> T	read(ByteProcessor<T> processor) Reads the contents of this byte source using the given processor to process bytes as they are read.
long	size() Returns the size of this source in bytes.
ByteSource	slice(long offset, long length) Returns a view of a slice of this byte source that is at most length bytes long starting at the given offset.
static ByteSource	wrap(byte[] b) Returns a view of the given byte array as a ByteSource.

Methods inherited from class java.lang.Object

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

Constructor Detail

ByteSource

protected ByteSource()

Constructor for use by subclasses.

Method Detail

asCharSource

public CharSource asCharSource(Charset charset)

Returns a CharSource view of this byte source that decodes bytes read from this source as characters using the given Charset.

openStream

public abstract InputStream openStream()
                                throws IOException

Opens a new InputStream for reading from this source. This method should return a new, independent stream each time it is called.

The caller is responsible for ensuring that the returned stream is closed.

Throws:

IOException - if an I/O error occurs in the process of opening the stream

openBufferedStream

public InputStream openBufferedStream()
                               throws IOException

Opens a new buffered InputStream for reading from this source. The returned stream is not required to be a BufferedInputStream in order to allow implementations to simply delegate to openStream() when the stream returned by that method does not benefit from additional buffering (for example, a ByteArrayInputStream). This method should return a new, independent stream each time it is called.

The caller is responsible for ensuring that the returned stream is closed.

Throws:

IOException - if an I/O error occurs in the process of opening the stream

Since:

15.0 (in 14.0 with return type BufferedInputStream)

slice

public ByteSource slice(long offset,
               long length)

Returns a view of a slice of this byte source that is at most length bytes long starting at the given offset.

Throws:

IllegalArgumentException - if offset or length is negative

isEmpty

public boolean isEmpty()
                throws IOException

Returns whether the source has zero bytes. The default implementation is to open a stream and check for EOF.

Throws:

IOException - if an I/O error occurs

Since:

15.0

size

public long size()
          throws IOException

Returns the size of this source in bytes. For most implementations, this is a heavyweight operation that will open a stream, read (or skip, if possible) to the end of the stream and return the total number of bytes that were read.

For some sources, such as a file, this method may use a more efficient implementation. Note that in such cases, it is possible that this method will return a different number of bytes than would be returned by reading all of the bytes (for example, some special files may return a size of 0 despite actually having content when read).

In either case, if this is a mutable source such as a file, the size it returns may not be the same number of bytes a subsequent read would return.

Throws:

IOException - if an I/O error occurs in the process of reading the size of this source

copyTo

public long copyTo(OutputStream output)
            throws IOException

Copies the contents of this byte source to the given OutputStream. Does not close output.

Throws:

IOException - if an I/O error occurs in the process of reading from this source or writing to output

copyTo

public long copyTo(ByteSink sink)
            throws IOException

Copies the contents of this byte source to the given ByteSink.

Throws:

IOException - if an I/O error occurs in the process of reading from this source or writing to sink

read

public byte[] read()
            throws IOException

Reads the full contents of this byte source as a byte array.

Throws:

IOException - if an I/O error occurs in the process of reading from this source

read

@Beta
public <T> T read(ByteProcessor<T> processor)
       throws IOException

Reads the contents of this byte source using the given processor to process bytes as they are read. Stops when all bytes have been read or the consumer returns false. Returns the result produced by the processor.

Throws:

IOException - if an I/O error occurs in the process of reading from this source or if processor throws an IOException

Since:

16.0

hash

public HashCode hash(HashFunction hashFunction)
              throws IOException

Hashes the contents of this byte source using the given hash function.

Throws:

IOException - if an I/O error occurs in the process of reading from this source

contentEquals

public boolean contentEquals(ByteSource other)
                      throws IOException

Checks that the contents of this byte source are equal to the contents of the given byte source.

Throws:

IOException - if an I/O error occurs in the process of reading from this source or other

concat

public static ByteSource concat(Iterable<? extends ByteSource> sources)

Concatenates multiple ByteSource instances into a single source. Streams returned from the source will contain the concatenated data from the streams of the underlying sources.

Only one underlying stream will be open at a time. Closing the concatenated stream will close the open underlying stream.

Parameters:

sources - the sources to concatenate

Returns:

a ByteSource containing the concatenated data

Since:

15.0

concat

public static ByteSource concat(Iterator<? extends ByteSource> sources)

Concatenates multiple ByteSource instances into a single source. Streams returned from the source will contain the concatenated data from the streams of the underlying sources.

Only one underlying stream will be open at a time. Closing the concatenated stream will close the open underlying stream.

Note: The input Iterator will be copied to an ImmutableList when this method is called. This will fail if the iterator is infinite and may cause problems if the iterator eagerly fetches data for each source when iterated (rather than producing sources that only load data through their streams). Prefer using the concat(Iterable) overload if possible.

Parameters:

sources - the sources to concatenate

Returns:

a ByteSource containing the concatenated data

Throws:

NullPointerException - if any of sources is null

Since:

15.0

concat

public static ByteSource concat(ByteSource... sources)

Concatenates multiple ByteSource instances into a single source. Streams returned from the source will contain the concatenated data from the streams of the underlying sources.

Only one underlying stream will be open at a time. Closing the concatenated stream will close the open underlying stream.

Parameters:

sources - the sources to concatenate

Returns:

a ByteSource containing the concatenated data

Throws:

NullPointerException - if any of sources is null

Since:

15.0

wrap

public static ByteSource wrap(byte[] b)

Returns a view of the given byte array as a ByteSource. To view only a specific range in the array, use ByteSource.wrap(b).slice(offset, length).

Since:

15.0 (since 14.0 as ByteStreams.asByteSource(byte[])).

empty

public static ByteSource empty()

Returns an immutable ByteSource that contains no bytes.

Since:

15.0