@InterfaceAudience.Public @InterfaceStability.Stable public class FSDataInputStream extends DataInputStream implements Seekable, PositionedReadable, ByteBufferReadable, org.apache.hadoop.fs.HasFileDescriptor, CanSetDropBehind, CanSetReadahead, org.apache.hadoop.fs.HasEnhancedByteBufferAccess, CanUnbuffer, StreamCapabilities
FSInputStream
in a DataInputStream
and buffers input through a BufferedInputStream
.in
DROPBEHIND, HFLUSH, HSYNC, READAHEAD, UNBUFFER
Constructor and Description |
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FSDataInputStream(InputStream in) |
Modifier and Type | Method and Description |
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FileDescriptor |
getFileDescriptor() |
long |
getPos()
Get the current position in the input stream.
|
boolean |
hasCapability(String capability)
Query the stream for a specific capability.
|
int |
read(ByteBuffer buf)
Reads up to buf.remaining() bytes into buf.
|
ByteBuffer |
read(ByteBufferPool bufferPool,
int maxLength) |
ByteBuffer |
read(ByteBufferPool bufferPool,
int maxLength,
EnumSet<ReadOption> opts)
Get a ByteBuffer containing file data.
|
int |
read(long position,
byte[] buffer,
int offset,
int length)
Read bytes from the given position in the stream to the given buffer.
|
void |
readFully(long position,
byte[] buffer)
|
void |
readFully(long position,
byte[] buffer,
int offset,
int length)
Read bytes from the given position in the stream to the given buffer.
|
void |
releaseBuffer(ByteBuffer buffer)
Release a ByteBuffer which was created by the enhanced ByteBuffer read
function.
|
void |
seek(long desired)
Seek to the given offset.
|
boolean |
seekToNewSource(long targetPos)
Seek to the given position on an alternate copy of the data.
|
void |
setDropBehind(Boolean dropBehind)
Configure whether the stream should drop the cache.
|
void |
setReadahead(Long readahead)
Set the readahead on this stream.
|
String |
toString()
String value.
|
void |
unbuffer()
Reduce the buffering.
|
read, read, readBoolean, readByte, readChar, readDouble, readFloat, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF, readUTF, skipBytes
available, close, mark, markSupported, read, reset, skip
public FSDataInputStream(InputStream in)
public void seek(long desired) throws IOException
seek
in interface Seekable
desired
- offset to seek toIOException
public long getPos() throws IOException
getPos
in interface Seekable
IOException
public int read(long position, byte[] buffer, int offset, int length) throws IOException
read
in interface PositionedReadable
position
- position in the input stream to seekbuffer
- buffer into which data is readoffset
- offset into the buffer in which data is writtenlength
- maximum number of bytes to read-1
if there is no more data because the end of the stream has been
reachedIOException
- IO problems.public void readFully(long position, byte[] buffer, int offset, int length) throws IOException
length
bytes have been read.readFully
in interface PositionedReadable
position
- position in the input stream to seekbuffer
- buffer into which data is readoffset
- offset into the buffer in which data is writtenlength
- the number of bytes to readIOException
- IO problemsEOFException
- If the end of stream is reached while reading.
If an exception is thrown an undetermined number
of bytes in the buffer may have been written.public void readFully(long position, byte[] buffer) throws IOException
readFully
in interface PositionedReadable
position
- position within filebuffer
- destination bufferIOException
- IO problems.EOFException
- the end of the data was reached before
the read operation completedpublic boolean seekToNewSource(long targetPos) throws IOException
targetPos
- position to seek toIOException
public int read(ByteBuffer buf) throws IOException
ByteBufferReadable
UnsupportedOperationException
, so
callers that are not confident in support for this method from the
underlying filesystem should be prepared to handle that exception.
Implementations should treat 0-length requests as legitimate, and must not
signal an error upon their receipt.read
in interface ByteBufferReadable
buf
- the ByteBuffer to receive the results of the read operation.IOException
- if there is some error performing the readpublic FileDescriptor getFileDescriptor() throws IOException
getFileDescriptor
in interface org.apache.hadoop.fs.HasFileDescriptor
IOException
public void setReadahead(Long readahead) throws IOException, UnsupportedOperationException
CanSetReadahead
setReadahead
in interface CanSetReadahead
readahead
- The readahead to use. null means to use the default.IOException
- If there was an error changing the dropBehind
setting.
UnsupportedOperationException If this stream doesn't support
setting readahead.UnsupportedOperationException
public void setDropBehind(Boolean dropBehind) throws IOException, UnsupportedOperationException
CanSetDropBehind
setDropBehind
in interface CanSetDropBehind
dropBehind
- Whether to drop the cache. null means to use the
default value.IOException
- If there was an error changing the dropBehind
setting.
UnsupportedOperationException If this stream doesn't support
setting the drop-behind.UnsupportedOperationException
public ByteBuffer read(ByteBufferPool bufferPool, int maxLength, EnumSet<ReadOption> opts) throws IOException, UnsupportedOperationException
org.apache.hadoop.fs.HasEnhancedByteBufferAccess
read
in interface org.apache.hadoop.fs.HasEnhancedByteBufferAccess
bufferPool
- If this is non-null, it will be used to create a fallback
ByteBuffer when the stream itself cannot create one.maxLength
- The maximum length of buffer to return. We may return a buffer
which is shorter than this.opts
- Options to use when reading.IOException
UnsupportedOperationException
public final ByteBuffer read(ByteBufferPool bufferPool, int maxLength) throws IOException, UnsupportedOperationException
public void releaseBuffer(ByteBuffer buffer)
org.apache.hadoop.fs.HasEnhancedByteBufferAccess
releaseBuffer
in interface org.apache.hadoop.fs.HasEnhancedByteBufferAccess
buffer
- The ByteBuffer to release.public void unbuffer()
CanUnbuffer
unbuffer
in interface CanUnbuffer
public boolean hasCapability(String capability)
StreamCapabilities
hasCapability
in interface StreamCapabilities
capability
- string to query the stream support for.Copyright © 2021 Apache Software Foundation. All rights reserved.