Interface DataFileHandle
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- All Known Implementing Classes:
LocalDataFileHandle
public interface DataFileHandle
DataFileHandle
provides a random-access handle to a file.
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description void
close()
Closes this random access file stream and releases any system resources associated with the stream.boolean
isReadOnly()
Returns true if this data file handle is open read-only.long
length()
Returns the length of this file.void
read(byte[] b)
Readsb.length
bytes from this file into the byte array, starting at the current file pointer.void
read(byte[] b, int off, int len)
Reads exactlylen
bytes from this file into the byte array, starting at the current file pointer.void
seek(long pos)
Sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs.void
setLength(long newLength)
Sets the length of this file.int
skipBytes(int n)
Attempts to skip overn
bytes of input discarding the skipped bytes.void
write(byte[] b)
Writesb.length
bytes from the specified byte array to this file, starting at the current file pointer.void
write(byte[] b, int off, int len)
Writeslen
bytes from the specified byte array starting at offsetoff
to this file.void
write(int b)
Writes the specified byte to this file.
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Method Detail
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isReadOnly
boolean isReadOnly() throws java.io.IOException
Returns true if this data file handle is open read-only.- Throws:
java.io.IOException
- if an I/O error occurs.
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read
void read(byte[] b) throws java.io.IOException
Readsb.length
bytes from this file into the byte array, starting at the current file pointer. This method reads repeatedly from the file until the requested number of bytes are read. This method blocks until the requested number of bytes are read, the end of the stream is detected, or an exception is thrown.- Parameters:
b
- the buffer into which the data is read.- Throws:
java.io.EOFException
- if this file reaches the end before reading all the bytes.java.io.IOException
- if an I/O error occurs.
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read
void read(byte[] b, int off, int len) throws java.io.IOException
Reads exactlylen
bytes from this file into the byte array, starting at the current file pointer. This method reads repeatedly from the file until the requested number of bytes are read. This method blocks until the requested number of bytes are read, the end of the stream is detected, or an exception is thrown.- Parameters:
b
- the buffer into which the data is read.off
- the start offset of the data.len
- the number of bytes to read.- Throws:
java.io.EOFException
- if this file reaches the end before reading all the bytes.java.io.IOException
- if an I/O error occurs.
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skipBytes
int skipBytes(int n) throws java.io.IOException
Attempts to skip overn
bytes of input discarding the skipped bytes.This method may skip over some smaller number of bytes, possibly zero. This may result from any of a number of conditions; reaching end of file before
n
bytes have been skipped is only one possibility. This method never throws anEOFException
. The actual number of bytes skipped is returned. Ifn
is negative, no bytes are skipped.- Parameters:
n
- the number of bytes to be skipped.- Returns:
- the actual number of bytes skipped.
- Throws:
java.io.IOException
- if an I/O error occurs.
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write
void write(int b) throws java.io.IOException
Writes the specified byte to this file. The write starts at the current file pointer.- Parameters:
b
- thebyte
to be written.- Throws:
java.io.IOException
- if an I/O error occurs.
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write
void write(byte[] b) throws java.io.IOException
Writesb.length
bytes from the specified byte array to this file, starting at the current file pointer.- Parameters:
b
- the data.- Throws:
java.io.IOException
- if an I/O error occurs.
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write
void write(byte[] b, int off, int len) throws java.io.IOException
Writeslen
bytes from the specified byte array starting at offsetoff
to this file.- Parameters:
b
- the data.off
- the start offset in the data.len
- the number of bytes to write.- Throws:
java.io.IOException
- if an I/O error occurs.
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seek
void seek(long pos) throws java.io.IOException
Sets the file-pointer offset, measured from the beginning of this file, at which the next read or write occurs. The offset may be set beyond the end of the file. Setting the offset beyond the end of the file does not change the file length. The file length will change only by writing after the offset has been set beyond the end of the file.- Parameters:
pos
- the offset position, measured in bytes from the beginning of the file, at which to set the file pointer.- Throws:
java.io.IOException
- ifpos
is less than0
or if an I/O error occurs.
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length
long length() throws java.io.IOException
Returns the length of this file.- Returns:
- the length of this file, measured in bytes.
- Throws:
java.io.IOException
- if an I/O error occurs.
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setLength
void setLength(long newLength) throws java.io.IOException
Sets the length of this file.If the present length of the file as returned by the
length
method is greater than thenewLength
argument then the file will be truncated. In this case, if the file offset as returned by thegetFilePointer
method is greater thennewLength
then after this method returns the offset will be equal tonewLength
.If the present length of the file as returned by the
length
method is smaller than thenewLength
argument then the file will be extended. In this case, the contents of the extended portion of the file are not defined.- Parameters:
newLength
- The desired length of the file- Throws:
java.io.IOException
- If an I/O error occurs
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close
void close() throws java.io.IOException
Closes this random access file stream and releases any system resources associated with the stream. A closed random access file cannot perform input or output operations and cannot be reopened.- Throws:
java.io.IOException
- if an I/O error occurs.
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