alluxio.client

Interface PositionedReadable

All Known Implementing Classes:

AlluxioFileInStream, AlluxioHdfsInputStream, BlockInStream, FileInStream, LocalCacheFileInStream

public interface PositionedReadable

Stream that permits positional reading.

Method Summary

Modifier and Type	Method and Description
int	positionedRead(long position, byte[] buffer, int offset, int length) Reads up to the specified number of bytes, from a given position within a file, and return the number of bytes read.

Method Detail

positionedRead

int positionedRead(long position,
                   byte[] buffer,
                   int offset,
                   int length)
            throws IOException

Reads up to the specified number of bytes, from a given position within a file, and return the number of bytes read. This does not change the current offset of a file, and is thread-safe. Not all implementations meet the thread safety requirement. According to the documentation of the PositionedReadable interface in Hadoop, those that do not meet the requirement cannot be used as a backing store for some applications, such as Apache HBase. All implementations of this interface in Alluxio must meet the thread safety requirement.

Parameters:

position - position within file

buffer - destination buffer

offset - offset in the buffer

length - number of bytes to read

Returns:

actual number of bytes read; -1 means "EOF";

Throws:

IOException