ByteSource (Guava: Google Core Libraries for Java 29.0-jre API)

java.lang.Object
- com.google.common.io.ByteSource

```
@GwtIncompatible
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.

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

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete 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, even if doing so requires opening and traversing an entire stream.
`Optional<Long>`	`sizeIfKnown()` Returns the size of this source in bytes, if the size can be easily determined without actually opening the data stream.
`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.
    If CharSource.asByteSource(java.nio.charset.Charset) is called on the returned source with the same charset, the default implementation of this method will ensure that the original ByteSource is returned, rather than round-trip encoding. Subclasses that override this method should behave the same way.
  - openStream
```
public abstract InputStream openStream()
                                throws IOException
```
    Opens a new InputStream for reading from this source. This method returns 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 while 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 returns 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 while 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. If offset is greater than the size of this source, the returned source will be empty. If offset + length is greater than the size of this source, the returned source will contain the slice starting at offset and ending at the end of this source.
    
    Throws:
    
    IllegalArgumentException - if offset or length is negative
  - isEmpty
```
public boolean isEmpty()
                throws IOException
```
    Returns whether the source has zero bytes. The default implementation first checks sizeIfKnown(), returning true if it's known to be zero and false if it's known to be non-zero. If the size is not known, it falls back to opening a stream and checking for EOF.
    Note that, in cases where sizeIfKnown returns zero, it is possible that bytes are actually available for reading. (For example, some special files may return a size of 0 despite actually having content when read.) This means that a source may return true from isEmpty() despite having readable content.
    
    Throws:
    
    IOException - if an I/O error occurs
    
    Since:
    
    15.0
  - sizeIfKnown
```
@Beta
public Optional<Long> sizeIfKnown()
```
    Returns the size of this source in bytes, if the size can be easily determined without actually opening the data stream.
    The default implementation returns Optional.absent(). Some sources, such as a file, may return a non-absent value. 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).
    Additionally, for mutable sources such as files, a subsequent read may return a different number of bytes if the contents are changed.
    
    Since:
    
    19.0
  - size
```
public long size()
          throws IOException
```
    Returns the size of this source in bytes, even if doing so requires opening and traversing an entire stream. To avoid a potentially expensive operation, see sizeIfKnown().
    The default implementation calls sizeIfKnown() and returns the value if present. If absent, it will fall back to 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.
    Note that for some sources that implement sizeIfKnown() to provide a more efficient implementation, 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, for mutable sources such as files, a subsequent read may return a different number of bytes if the contents are changed.
    
    Throws:
    
    IOException - if an I/O error occurs while reading the size of this source
  - copyTo
```
@CanIgnoreReturnValue
public long copyTo(OutputStream output)
                                  throws IOException
```
    Copies the contents of this byte source to the given OutputStream. Does not close output.
    
    Returns:
    
    the number of bytes copied
    
    Throws:
    
    IOException - if an I/O error occurs while reading from this source or writing to output
  - copyTo
```
@CanIgnoreReturnValue
public long copyTo(ByteSink sink)
                                  throws IOException
```
    Copies the contents of this byte source to the given ByteSink.
    
    Returns:
    
    the number of bytes copied
    
    Throws:
    
    IOException - if an I/O error occurs while 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 while reading from this source
  - read
```
@Beta
 @CanIgnoreReturnValue
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 while 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 while 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 while 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).
    Note that the given byte array may be be passed directly to methods on, for example, OutputStream (when copyTo(OutputStream) is called on the resulting ByteSource). This could allow a malicious OutputStream implementation to modify the contents of the array, but provides better performance in the normal case.
    
    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

Class ByteSource

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

ByteSource

Method Detail

asCharSource

openStream

openBufferedStream

slice

isEmpty

sizeIfKnown

size

copyTo

copyTo

read

read

hash

contentEquals

concat

concat

concat

wrap

empty