org.apache.hadoop.hdfs

类 DFSClient.RemoteBlockReader

java.lang.Object

java.io.InputStream

org.apache.hadoop.fs.FSInputStream

org.apache.hadoop.fs.FSInputChecker

org.apache.hadoop.hdfs.DFSClient.RemoteBlockReader

所有已实现的接口:

Closeable, AutoCloseable, PositionedReadable, Seekable, BlockReader

封闭类:

DFSClient

public static class DFSClient.RemoteBlockReader
extends FSInputChecker
implements BlockReader

This is a wrapper around connection to datadone and understands checksum, offset etc

字段概要

从类继承的字段 org.apache.hadoop.fs.FSInputChecker

file, LOG

构造器概要

构造器

限定符	构造器和说明
protected	DFSClient.RemoteBlockReader(Path file, int numRetries, DataChecksum checksum, boolean verifyChecksum)

方法概要

方法

限定符和类型	方法和说明
void	close()
protected long	getChunkPosition(long pos) Return position of beginning of chunk containing pos.
static BlockReader	newBlockReader(Socket sock, String file, long blockId, Token<BlockTokenIdentifier> accessToken, long genStamp, long startOffset, long len, int bufferSize)
static BlockReader	newBlockReader(Socket sock, String file, long blockId, Token<BlockTokenIdentifier> accessToken, long genStamp, long startOffset, long len, int bufferSize, boolean verifyChecksum) Creates a new BlockReader for the given blockId.
static BlockReader	newBlockReader(Socket sock, String file, long blockId, Token<BlockTokenIdentifier> accessToken, long genStamp, long startOffset, long len, int bufferSize, boolean verifyChecksum, String clientName)
int	read() Read one checksum-verified byte
int	read(byte[] buf, int off, int len) Read checksum verified bytes from this byte-input stream into the specified byte array, starting at the given offset.
int	readAll(byte[] buf, int offset, int len) kind of like readFully().
protected int	readChunk(long pos, byte[] buf, int offset, int len, byte[] checksumBuf) Reads in next checksum chunk data into buf at offset and checksum into checksum.
void	seek(long pos) Seek to the given position in the stream.
boolean	seekToNewSource(long targetPos) Seeks a different copy of the data.
long	skip(long n) Skips over and discards n bytes of data from the input stream.

从类继承的方法 org.apache.hadoop.fs.FSInputChecker

available, checksum2long, getPos, mark, markSupported, needChecksum, readFully, reset, set

从类继承的方法 org.apache.hadoop.fs.FSInputStream

read, readFully, readFully

从类继承的方法 java.io.InputStream

read

从类继承的方法 java.lang.Object

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

构造器详细资料

DFSClient.RemoteBlockReader

protected DFSClient.RemoteBlockReader(Path file,
                           int numRetries,
                           DataChecksum checksum,
                           boolean verifyChecksum)

方法详细资料

read

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

从类复制的说明: FSInputChecker

Read checksum verified bytes from this byte-input stream into the specified byte array, starting at the given offset.

This method implements the general contract of the corresponding read method of the InputStream class. As an additional convenience, it attempts to read as many bytes as possible by repeatedly invoking the read method of the underlying stream. This iterated read continues until one of the following conditions becomes true:

• The specified number of bytes have been read,
• The read method of the underlying stream returns -1, indicating end-of-file.

If the first read on the underlying stream returns -1 to indicate end-of-file then this method returns -1. Otherwise this method returns the number of bytes actually read.

指定者:

read 在接口中 BlockReader

覆盖:

read 在类中 FSInputChecker

参数:

buf - destination buffer.

off - offset at which to start storing bytes.

len - maximum number of bytes to read.

返回:

the number of bytes read, or -1 if the end of the stream has been reached.

抛出:

IOException - if an I/O error occurs. ChecksumException if any checksum error occurs

skip

public long skip(long n)
          throws IOException

从类复制的说明: FSInputChecker

Skips over and discards n bytes of data from the input stream.

This method may skip more bytes than are remaining in the backing file. This produces no exception and the number of bytes skipped may include some number of bytes that were beyond the EOF of the backing file. Attempting to read from the stream after skipping past the end will result in -1 indicating the end of the file.

If n is negative, no bytes are skipped.

指定者:

skip 在接口中 BlockReader

覆盖:

skip 在类中 FSInputChecker

参数:

n - the number of bytes to be skipped.

返回:

the actual number of bytes skipped.

抛出:

IOException - if an I/O error occurs. ChecksumException if the chunk to skip to is corrupted

read

public int read()
         throws IOException

从类复制的说明: FSInputChecker

Read one checksum-verified byte

覆盖:

read 在类中 FSInputChecker

返回:

the next byte of data, or -1 if the end of the stream is reached.

抛出:

IOException - if an I/O error occurs.

seekToNewSource

public boolean seekToNewSource(long targetPos)
                        throws IOException

从类复制的说明: FSInputStream

Seeks a different copy of the data. Returns true if found a new source, false otherwise.

指定者:

seekToNewSource 在接口中 Seekable

指定者:

seekToNewSource 在类中 FSInputStream

抛出:

IOException

seek

public void seek(long pos)
          throws IOException

从类复制的说明: FSInputChecker

Seek to the given position in the stream. The next read() will be from that position.

This method may seek past the end of the file. This produces no exception and an attempt to read from the stream will result in -1 indicating the end of the file.

指定者:

seek 在接口中 Seekable

覆盖:

seek 在类中 FSInputChecker

参数:

pos - the postion to seek to.

抛出:

IOException - if an I/O error occurs. ChecksumException if the chunk to seek to is corrupted

getChunkPosition

protected long getChunkPosition(long pos)

从类复制的说明: FSInputChecker

Return position of beginning of chunk containing pos.

指定者:

getChunkPosition 在类中 FSInputChecker

参数:

pos - a postion in the file

返回:

the starting position of the chunk which contains the byte

readChunk

protected int readChunk(long pos,
            byte[] buf,
            int offset,
            int len,
            byte[] checksumBuf)
                 throws IOException

从类复制的说明: FSInputChecker

Reads in next checksum chunk data into buf at offset and checksum into checksum. The method is used for implementing read, therefore, it should be optimized for sequential reading

指定者:

readChunk 在类中 FSInputChecker

参数:

pos - chunkPos

buf - desitination buffer

offset - offset in buf at which to store data

len - maximun number of bytes to read

返回:

number of bytes read

抛出:

IOException

newBlockReader

public static BlockReader newBlockReader(Socket sock,
                         String file,
                         long blockId,
                         Token<BlockTokenIdentifier> accessToken,
                         long genStamp,
                         long startOffset,
                         long len,
                         int bufferSize)
                                  throws IOException

抛出:

IOException

newBlockReader

public static BlockReader newBlockReader(Socket sock,
                         String file,
                         long blockId,
                         Token<BlockTokenIdentifier> accessToken,
                         long genStamp,
                         long startOffset,
                         long len,
                         int bufferSize,
                         boolean verifyChecksum)
                                  throws IOException

Creates a new BlockReader for the given blockId.

参数:

sock - Socket to read the block.

file - File to which this block belongs.

blockId - Block id.

accessToken - Block access token.

genStamp - Generation stamp of the block.

startOffset - Start offset for the data.

len - Length to be read.

bufferSize - Buffer size to use.

verifyChecksum - Checksum verification is required or not.

返回:

BlockReader object.

抛出:

IOException

newBlockReader

public static BlockReader newBlockReader(Socket sock,
                         String file,
                         long blockId,
                         Token<BlockTokenIdentifier> accessToken,
                         long genStamp,
                         long startOffset,
                         long len,
                         int bufferSize,
                         boolean verifyChecksum,
                         String clientName)
                                  throws IOException

抛出:

IOException

close

public void close()
           throws IOException

指定者:

close 在接口中 Closeable

指定者:

close 在接口中 AutoCloseable

覆盖:

close 在类中 InputStream

抛出:

IOException

readAll

public int readAll(byte[] buf,
          int offset,
          int len)
            throws IOException

kind of like readFully(). Only reads as much as possible. And allows use of protected readFully().

指定者:

readAll 在接口中 BlockReader

抛出:

IOException