public static class SequenceFile.Reader extends Object implements Closeable
构造器和说明 |
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SequenceFile.Reader(FileSystem fs,
Path file,
Configuration conf)
Open the named file.
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限定符和类型 | 方法和说明 |
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void |
close()
Close the file.
|
SequenceFile.ValueBytes |
createValueBytes() |
CompressionCodec |
getCompressionCodec()
Returns the compression codec of data in this file.
|
Object |
getCurrentValue(Object val)
Get the 'value' corresponding to the last read 'key'.
|
void |
getCurrentValue(Writable val)
Get the 'value' corresponding to the last read 'key'.
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Class<?> |
getKeyClass()
Returns the class of keys in this file.
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String |
getKeyClassName()
Returns the name of the key class.
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SequenceFile.Metadata |
getMetadata()
Returns the metadata object of the file
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long |
getPosition()
Return the current byte position in the input file.
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Class<?> |
getValueClass()
Returns the class of values in this file.
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String |
getValueClassName()
Returns the name of the value class.
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boolean |
isBlockCompressed()
Returns true if records are block-compressed.
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boolean |
isCompressed()
Returns true if values are compressed.
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int |
next(DataOutputBuffer buffer)
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Object |
next(Object key)
Read the next key in the file, skipping its
value.
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boolean |
next(Writable key)
Read the next key in the file into
key , skipping its
value. |
boolean |
next(Writable key,
Writable val)
Read the next key/value pair in the file into
key and
val . |
int |
nextRaw(DataOutputBuffer key,
SequenceFile.ValueBytes val)
Read 'raw' records.
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int |
nextRawKey(DataOutputBuffer key)
Read 'raw' keys.
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int |
nextRawValue(SequenceFile.ValueBytes val)
Read 'raw' values.
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protected FSDataInputStream |
openFile(FileSystem fs,
Path file,
int bufferSize,
long length)
Override this method to specialize the type of
FSDataInputStream returned. |
void |
seek(long position)
Set the current byte position in the input file.
|
void |
sync(long position)
Seek to the next sync mark past a given position.
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boolean |
syncSeen()
Returns true iff the previous call to next passed a sync mark.
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String |
toString()
Returns the name of the file.
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public SequenceFile.Reader(FileSystem fs, Path file, Configuration conf) throws IOException
IOException
protected FSDataInputStream openFile(FileSystem fs, Path file, int bufferSize, long length) throws IOException
FSDataInputStream
returned.IOException
public void close() throws IOException
close
在接口中 Closeable
close
在接口中 AutoCloseable
IOException
public String getKeyClassName()
public Class<?> getKeyClass()
public String getValueClassName()
public Class<?> getValueClass()
public boolean isCompressed()
public boolean isBlockCompressed()
public CompressionCodec getCompressionCodec()
public SequenceFile.Metadata getMetadata()
public void getCurrentValue(Writable val) throws IOException
val
- : The 'value' to be read.IOException
public Object getCurrentValue(Object val) throws IOException
val
- : The 'value' to be read.IOException
public boolean next(Writable key) throws IOException
key
, skipping its
value. True if another entry exists, and false at end of file.IOException
public boolean next(Writable key, Writable val) throws IOException
key
and
val
. Returns true if such a pair exists and false when at
end of fileIOException
public int next(DataOutputBuffer buffer) throws IOException
IOException
public SequenceFile.ValueBytes createValueBytes()
public int nextRaw(DataOutputBuffer key, SequenceFile.ValueBytes val) throws IOException
key
- - The buffer into which the key is readval
- - The 'raw' valueIOException
public int nextRawKey(DataOutputBuffer key) throws IOException
key
- - The buffer into which the key is readIOException
public Object next(Object key) throws IOException
IOException
public int nextRawValue(SequenceFile.ValueBytes val) throws IOException
val
- - The 'raw' valueIOException
public void seek(long position) throws IOException
The position passed must be a position returned by SequenceFile.Writer.getLength()
when writing this file. To seek to an arbitrary
position, use sync(long)
.
IOException
public void sync(long position) throws IOException
IOException
public boolean syncSeen()
public long getPosition() throws IOException
IOException
Copyright © 2009 The Apache Software Foundation