com.pervasive.datarush.io

Interface DataSplit

All Superinterfaces:

Serializable

All Known Implementing Classes:

CompressedFileSplit, FileSplit, SplittableCompressedFileSplit

public interface DataSplit
extends Serializable

Describes a range of bytes from a data source. Ranges are identified by a start offset and a length. DataSplit objects are used to describe how data sources can be divided into pieces which can then be parsed in parallel.

Method Summary

Methods

Modifier and Type	Method and Description
DataSplit	authorize(FileClient client) Creates an identical split which will use the specified authorization context for access.
FileClient	getFileClient() Return the file client associated with this split.
long	getLength() Gets the length of the split, in bytes.
Path	getPath() Gets the path to the file on which the split is defined.
long	getStartOffset() Gets the byte offset of the beginning of the split.
InputStream	openSource() Opens the underlying source for access.
SplitInputStream	openSplit(int buffer) Opens the split for reading using the specified size for the read buffer.

Method Detail

getPath

Path getPath()

Gets the path to the file on which the split is defined.

Some splits may not represent a file; in this case, null is returned.

Returns:

the path to the underlying source file.

getStartOffset

long getStartOffset()

Gets the byte offset of the beginning of the split.

Returns:

the position of the first byte of the split

getLength

long getLength()

Gets the length of the split, in bytes.

Returns:

the size of the split

openSplit

SplitInputStream openSplit(int buffer)
                           throws IOException

Opens the split for reading using the specified size for the read buffer. The reader will initially be positioned at the first byte of the split. The reader will indicate when the last byte of the split has been read via SplitInputStreamImpl.hasOverrun().

Parameters:

buffer - the size of the buffer to use for reads, in bytes

Returns:

a reader of the data in the split

Throws:

IOException - if an I/O error occurs opening the underlying source

openSource

InputStream openSource()
                       throws IOException

Opens the underlying source for access. Initially, the stream is positioned at the first byte of the source. Unlike openSplit(int), the caller is responsible for making sure accesses are aligned to split boundaries. The stream is also unbuffered.

This method may be required for dealing with formats which store metadata at the beginning of the file.

Returns:

a reader of the data in the underlying source

Throws:

IOException - if an I/O error occurs opening the underlying source

authorize

DataSplit authorize(FileClient client)

Creates an identical split which will use the specified authorization context for access.

This method is used by clients of the IO APIs which want to provide an alternative to the OS-level authorization inherited from the JVM's execution environment. Data access methods for the split will use the supplied context.

The authorization context is not a serializable attribute of a data split, as it represents the environment in which the data in accesses, not a property of the data itself. The context is associated with the split as a matter of convenience.

Parameters:

client - the authorization context to use for access

Returns:

a split using the provided authorization context

getFileClient

FileClient getFileClient()

Return the file client associated with this split. The file client can be used to provide filesystem specific context.

May return null depending on the state.

Returns:

FileClient associated with this split.