ucar.unidata.io
Class RandomAccessFile

java.lang.Object
  extended by ucar.unidata.io.RandomAccessFile
All Implemented Interfaces:
DataInput, DataOutput
Direct Known Subclasses:
HTTPRandomAccessFile, InMemoryRandomAccessFile

@NotThreadSafe
public class RandomAccessFile
extends Object
implements DataInput, DataOutput

A buffered drop-in replacement for java.io.RandomAccessFile. Instances of this class realise substantial speed increases over java.io.RandomAccessFile through the use of buffering. This is a subclass of Object, as it was not possible to subclass java.io.RandomAccessFile because many of the methods are final. However, if it is necessary to use RandomAccessFile and java.io.RandomAccessFile interchangeably, both classes implement the DataInput and DataOutput interfaces.

By Russ Rew, based on BufferedRandomAccessFile by Alex McManus, based on Sun's source code for java.io.RandomAccessFile. For Alex McManus version from which this derives, see his Freeware Java Classes.

Author:
Alex McManus, Russ Rew, john caron
See Also:
DataInput, DataOutput, RandomAccessFile

Field Summary
protected static Set<String> allFiles
           
static int BIG_ENDIAN
           
protected  boolean bigEndian
          The current endian (big or little) mode of the file.
protected  byte[] buffer
          The buffer used for reading the data.
protected  long bufferStart
          The offset in bytes of the start of the buffer, from the start of the file.
protected  long dataEnd
          The offset in bytes of the end of the data in the buffer, from the start of the file.
protected  int dataSize
          The size of the data stored in the buffer, in bytes.
protected static boolean debugAccess
           
protected static boolean debugLeaks
           
protected static int defaultBufferSize
          The default buffer size, in bytes.
protected  boolean endOfFile
          True if we are at the end of the file.
protected  RandomAccessFile file
          The underlying java.io.RandomAccessFile.
protected  FileChannel fileChannel
           
protected  long filePosition
          The offset in bytes from the file start, of the next read or write operation.
static int LITTLE_ENDIAN
           
protected  String location
          File location
protected static List<String> openFiles
           
protected  boolean readonly
          The access mode of the file.
protected static boolean showOpen
           
protected static boolean showRead
           
 
Constructor Summary
protected RandomAccessFile(int bufferSize)
          Constructor, for subclasses
  RandomAccessFile(String location, String mode)
          Constructor, default buffer size.
  RandomAccessFile(String location, String mode, int bufferSize)
          Constructor.
 
Method Summary
 void close()
          Close the file, and release any associated system resources.
 void flush()
          Copy the contents of the buffer to the disk.
static List<String> getAllFiles()
           
 int getBufferSize()
          Get the buffer size
static boolean getDebugLeaks()
          Debugging, do not use.
static long getDebugNbytes()
           
static int getDebugNseeks()
           
 FileDescriptor getFD()
          Returns the opaque file descriptor object associated with this file.
 long getFilePointer()
          Returns the current position in the file, where the next read or write will occur.
 String getLocation()
          Get the file location, or name.
static List<String> getOpenFiles()
          Debugging, do not use.
 RandomAccessFile getRandomAccessFile()
          Allow access to the underlying java.io.RandomAccessFile.
 boolean isAtEndOfFile()
          Return true if file pointer is at end of file.
 long length()
          Get the length of the file.
 void order(int endian)
          Change the current endian mode.
protected  int read_(long pos, byte[] b, int offset, int len)
          Read directly from file, without going through the buffer.
 int read()
          Read a byte of data from the file, blocking until data is available.
 int read(byte[] b)
          Read up to b.length( ) bytes into an array.
 int read(byte[] b, int off, int len)
          Read up to len bytes into an array, at a specified offset.
 boolean readBoolean()
          Reads a boolean from this file.
protected  void readBuffer(long pos)
           
 byte readByte()
          Reads a signed 8-bit value from this file.
protected  int readBytes(byte[] b, int off, int len)
          Read up to len bytes into an array, at a specified offset.
 byte[] readBytes(int count)
          Read fully count number of bytes
 char readChar()
          Reads a Unicode character from this file.
 double readDouble()
          Reads a double from this file.
 void readDouble(double[] pa, int start, int n)
          Read an array of doubles
 float readFloat()
          Reads a float from this file.
 void readFloat(float[] pa, int start, int n)
          Read an array of floats
 void readFully(byte[] b)
          Reads b.length bytes from this file into the byte array.
 void readFully(byte[] b, int off, int len)
          Reads exactly len bytes from this file into the byte array.
 int readInt()
          Reads a signed 32-bit integer from this file.
 void readInt(int[] pa, int start, int n)
          Read an array of ints
 int readIntUnbuffered(long pos)
          Read an integer at the given position, bypassing all buffering.
 String readLine()
          Reads the next line of text from this file.
 long readLong()
          Reads a signed 64-bit integer from this file.
 void readLong(long[] pa, int start, int n)
          Read an array of longs
 short readShort()
          Reads a signed 16-bit number from this file.
 void readShort(short[] pa, int start, int n)
          Read an array of shorts
 String readString(int nbytes)
          Read a String of knoen length.
 long readToByteChannel(WritableByteChannel dest, long offset, long nbytes)
          Read nbytes bytes, at the specified file offset, send to a WritableByteChannel.
 int readUnsignedByte()
          Reads an unsigned 8-bit number from this file.
 int readUnsignedShort()
          Reads an unsigned 16-bit number from this file.
 String readUTF()
          Reads in a string from this file.
 boolean searchForward(KMPMatch match, int maxBytes)
          Search forward from the current pos, looking for a match.
 void seek(long pos)
          Set the position in the file for the next read or write.
 void setBufferSize(int bufferSize)
          Set the buffer size.
static void setDebugAccess(boolean b)
          Debugging, do not use.
static void setDebugLeaks(boolean b)
          Debugging, do not use.
 void setExtendMode()
          Set extendMode for truncated, yet valid files - old NetCDF code allowed this when NOFILL on, and user doesnt write all variables.
 void setMinLength(long minLength)
          Make sure file is at least this long when its closed.
 int skipBytes(int n)
          Skips exactly n bytes of input.
 String toString()
          Create a string representation of this object.
 void unread()
          Unread the last byte read.
 void write(byte[] b)
          Writes b.length bytes from the specified byte array starting at offset off to this file.
 void write(byte[] b, int off, int len)
          Writes len bytes from the specified byte array starting at offset off to this file.
 void write(int b)
          Write a byte to the file.
 void writeBoolean(boolean v)
          Writes a boolean to the file as a 1-byte value.
 void writeBoolean(boolean[] pa, int start, int n)
          Write an array of booleans
 void writeByte(int v)
          Writes a byte to the file as a 1-byte value.
 void writeBytes(byte[] b, int off, int len)
          Write len bytes from an array to the file.
 void writeBytes(char[] b, int off, int len)
          Writes the character array to the file as a sequence of bytes.
 void writeBytes(String s)
          Writes the string to the file as a sequence of bytes.
 void writeChar(char[] pa, int start, int n)
          Write an array of chars
 void writeChar(int v)
          Writes a char to the file as a 2-byte value, high byte first.
 void writeChars(String s)
          Writes a string to the file as a sequence of characters.
 void writeDouble(double v)
          Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.
 void writeDouble(double[] pa, int start, int n)
          Write an array of doubles
 void writeFloat(float v)
          Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.
 void writeFloat(float[] pa, int start, int n)
          Write an array of floats
 void writeInt(int v)
          Writes an int to the file as four bytes, high byte first.
 void writeInt(int[] pa, int start, int n)
          Write an array of ints
 void writeLong(long v)
          Writes a long to the file as eight bytes, high byte first.
 void writeLong(long[] pa, int start, int n)
          Write an array of longs
 void writeShort(int v)
          Writes a short to the file as two bytes, high byte first.
 void writeShort(short[] pa, int start, int n)
          Write an array of shorts
 void writeUTF(String str)
          Writes a string to the file using UTF-8 encoding in a machine-independent manner.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

BIG_ENDIAN

public static final int BIG_ENDIAN
See Also:
Constant Field Values

LITTLE_ENDIAN

public static final int LITTLE_ENDIAN
See Also:
Constant Field Values

debugLeaks

protected static boolean debugLeaks

debugAccess

protected static boolean debugAccess

allFiles

protected static Set<String> allFiles

openFiles

protected static List<String> openFiles

showOpen

protected static boolean showOpen

showRead

protected static boolean showRead

defaultBufferSize

protected static final int defaultBufferSize
The default buffer size, in bytes.

See Also:
Constant Field Values

location

protected String location
File location


file

protected RandomAccessFile file
The underlying java.io.RandomAccessFile.


fileChannel

protected FileChannel fileChannel

filePosition

protected long filePosition
The offset in bytes from the file start, of the next read or write operation.


buffer

protected byte[] buffer
The buffer used for reading the data.


bufferStart

protected long bufferStart
The offset in bytes of the start of the buffer, from the start of the file.


dataEnd

protected long dataEnd
The offset in bytes of the end of the data in the buffer, from the start of the file. This can be calculated from bufferStart + dataSize, but it is cached to speed up the read( ) method.


dataSize

protected int dataSize
The size of the data stored in the buffer, in bytes. This may be less than the size of the buffer.


endOfFile

protected boolean endOfFile
True if we are at the end of the file.


readonly

protected boolean readonly
The access mode of the file.


bigEndian

protected boolean bigEndian
The current endian (big or little) mode of the file.

Constructor Detail

RandomAccessFile

protected RandomAccessFile(int bufferSize)
Constructor, for subclasses

Parameters:
bufferSize - size of read buffer

RandomAccessFile

public RandomAccessFile(String location,
                        String mode)
                 throws IOException
Constructor, default buffer size.

Parameters:
location - location of the file
mode - same as for java.io.RandomAccessFile
Throws:
IOException - on open error

RandomAccessFile

public RandomAccessFile(String location,
                        String mode,
                        int bufferSize)
                 throws IOException
Constructor.

Parameters:
location - location of the file
mode - same as for java.io.RandomAccessFile
bufferSize - size of buffer to use.
Throws:
IOException - on open error
Method Detail

getDebugLeaks

public static boolean getDebugLeaks()
Debugging, do not use.

Returns:
true if debugLeaks is on

setDebugLeaks

public static void setDebugLeaks(boolean b)
Debugging, do not use.

Parameters:
b - set true to track java.io.RandomAccessFile

getOpenFiles

public static List<String> getOpenFiles()
Debugging, do not use.

Returns:
list of open files.

getAllFiles

public static List<String> getAllFiles()

setDebugAccess

public static void setDebugAccess(boolean b)
Debugging, do not use.

Parameters:
b - to debug file reading

getDebugNseeks

public static int getDebugNseeks()

getDebugNbytes

public static long getDebugNbytes()

getRandomAccessFile

public RandomAccessFile getRandomAccessFile()
Allow access to the underlying java.io.RandomAccessFile. WARNING! BROKEN ENCAPSOLATION, DO NOT USE. May change implementation in the future.

Returns:
the underlying java.io.RandomAccessFile.

setBufferSize

public void setBufferSize(int bufferSize)
Set the buffer size. If writing, call flush() first.

Parameters:
bufferSize - length in bytes

getBufferSize

public int getBufferSize()
Get the buffer size

Returns:
bufferSize length in bytes

close

public void close()
           throws IOException
Close the file, and release any associated system resources.

Throws:
IOException - if an I/O error occurrs.

isAtEndOfFile

public boolean isAtEndOfFile()
Return true if file pointer is at end of file.

Returns:
true if file pointer is at end of file

seek

public void seek(long pos)
          throws IOException
Set the position in the file for the next read or write.

Parameters:
pos - the offset (in bytes) from the start of the file.
Throws:
IOException - if an I/O error occurrs.

readBuffer

protected void readBuffer(long pos)
                   throws IOException
Throws:
IOException

getFilePointer

public long getFilePointer()
                    throws IOException
Returns the current position in the file, where the next read or write will occur.

Returns:
the offset from the start of the file in bytes.
Throws:
IOException - if an I/O error occurrs.

getLocation

public String getLocation()
Get the file location, or name.

Returns:
file location

length

public long length()
            throws IOException
Get the length of the file. The data in the buffer (which may not have been written the disk yet) is taken into account.

Returns:
the length of the file in bytes.
Throws:
IOException - if an I/O error occurrs.

order

public void order(int endian)
Change the current endian mode. Subsequent reads of short, int, float, double, long, char will use this. Does not currently affect writes. Default values is BIG_ENDIAN.

Parameters:
endian - RandomAccessFile.BIG_ENDIAN or RandomAccessFile.LITTLE_ENDIAN

getFD

public FileDescriptor getFD()
                     throws IOException
Returns the opaque file descriptor object associated with this file.

Returns:
the file descriptor object associated with this file.
Throws:
IOException - if an I/O error occurs.

flush

public void flush()
           throws IOException
Copy the contents of the buffer to the disk.

Throws:
IOException - if an I/O error occurs.

setMinLength

public void setMinLength(long minLength)
Make sure file is at least this long when its closed. needed when not using fill mode, and not all data is written.

Parameters:
minLength - minimum length of the file.

setExtendMode

public void setExtendMode()
Set extendMode for truncated, yet valid files - old NetCDF code allowed this when NOFILL on, and user doesnt write all variables.


read

public int read()
         throws IOException
Read a byte of data from the file, blocking until data is available.

Returns:
the next byte of data, or -1 if the end of the file is reached.
Throws:
IOException - if an I/O error occurrs.

readBytes

protected int readBytes(byte[] b,
                        int off,
                        int len)
                 throws IOException
Read up to len bytes into an array, at a specified offset. This will block until at least one byte has been read.

Parameters:
b - the byte array to receive the bytes.
off - the offset in the array where copying will start.
len - the number of bytes to copy.
Returns:
the actual number of bytes read, or -1 if there is not more data due to the end of the file being reached.
Throws:
IOException - if an I/O error occurrs.

readToByteChannel

public long readToByteChannel(WritableByteChannel dest,
                              long offset,
                              long nbytes)
                       throws IOException
Read nbytes bytes, at the specified file offset, send to a WritableByteChannel. This will block until all bytes are read. This uses the underlying file channel directly, bypassing all user buffers.

Parameters:
dest - write to this WritableByteChannel.
offset - the offset in the file where copying will start.
nbytes - the number of bytes to read.
Returns:
the actual number of bytes read and transfered
Throws:
IOException - if an I/O error occurs.

read_

protected int read_(long pos,
                    byte[] b,
                    int offset,
                    int len)
             throws IOException
Read directly from file, without going through the buffer. All reading goes through here or readToByteChannel;

Parameters:
pos - start here in the file
b - put data into this buffer
offset - buffer offset
len - this number of bytes
Returns:
actual number of bytes read
Throws:
IOException - on io error

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException
Read up to len bytes into an array, at a specified offset. This will block until at least one byte has been read.

Parameters:
b - the byte array to receive the bytes.
off - the offset in the array where copying will start.
len - the number of bytes to copy.
Returns:
the actual number of bytes read, or -1 if there is not more data due to the end of the file being reached.
Throws:
IOException - if an I/O error occurrs.

read

public int read(byte[] b)
         throws IOException
Read up to b.length( ) bytes into an array. This will block until at least one byte has been read.

Parameters:
b - the byte array to receive the bytes.
Returns:
the actual number of bytes read, or -1 if there is not more data due to the end of the file being reached.
Throws:
IOException - if an I/O error occurrs.

readBytes

public byte[] readBytes(int count)
                 throws IOException
Read fully count number of bytes

Parameters:
count - how many bytes tp read
Returns:
a byte array of length count, fully read in
Throws:
IOException - if an I/O error occurrs.

readFully

public final void readFully(byte[] b)
                     throws IOException
Reads b.length bytes from this file into the byte array. This method reads repeatedly from the file until all the bytes are read. This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readFully in interface DataInput
Parameters:
b - the buffer into which the data is read.
Throws:
EOFException - if this file reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

readFully

public final void readFully(byte[] b,
                            int off,
                            int len)
                     throws IOException
Reads exactly len bytes from this file into the byte array. This method reads repeatedly from the file until all the bytes are read. This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readFully in interface DataInput
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:
EOFException - if this file reaches the end before reading all the bytes.
IOException - if an I/O error occurs.

skipBytes

public int skipBytes(int n)
              throws IOException
Skips exactly n bytes of input. This method blocks until all the bytes are skipped, the end of the stream is detected, or an exception is thrown.

Specified by:
skipBytes in interface DataInput
Parameters:
n - the number of bytes to be skipped.
Returns:
the number of bytes skipped, which is always n.
Throws:
EOFException - if this file reaches the end before skipping all the bytes.
IOException - if an I/O error occurs.

unread

public void unread()
Unread the last byte read. This method should not be used more than once between reading operations, or strange things might happen.


write

public void write(int b)
           throws IOException
Write a byte to the file. If the file has not been opened for writing, an IOException will be raised only when an attempt is made to write the buffer to the file.

Caveat: the effects of seek( )ing beyond the end of the file are undefined.

Specified by:
write in interface DataOutput
Parameters:
b - write this byte
Throws:
IOException - if an I/O error occurrs.

writeBytes

public void writeBytes(byte[] b,
                       int off,
                       int len)
                throws IOException
Write len bytes from an array to the file.

Parameters:
b - the array containing the data.
off - the offset in the array to the data.
len - the length of the data.
Throws:
IOException - if an I/O error occurrs.

write

public void write(byte[] b)
           throws IOException
Writes b.length bytes from the specified byte array starting at offset off to this file.

Specified by:
write in interface DataOutput
Parameters:
b - the data.
Throws:
IOException - if an I/O error occurs.

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException
Writes len bytes from the specified byte array starting at offset off to this file.

Specified by:
write in interface DataOutput
Parameters:
b - the data.
off - the start offset in the data.
len - the number of bytes to write.
Throws:
IOException - if an I/O error occurs.

readBoolean

public final boolean readBoolean()
                          throws IOException
Reads a boolean from this file. This method reads a single byte from the file. A value of 0 represents false. Any other value represents true. This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:
readBoolean in interface DataInput
Returns:
the boolean value read.
Throws:
EOFException - if this file has reached the end.
IOException - if an I/O error occurs.

readByte

public final byte readByte()
                    throws IOException
Reads a signed 8-bit value from this file. This method reads a byte from the file. If the byte read is b, where 0 <= b <= 255, then the result is:

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:
readByte in interface DataInput
Returns:
the next byte of this file as a signed 8-bit byte.
Throws:
EOFException - if this file has reached the end.
IOException - if an I/O error occurs.

readUnsignedByte

public final int readUnsignedByte()
                           throws IOException
Reads an unsigned 8-bit number from this file. This method reads a byte from this file and returns that byte.

This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.

Specified by:
readUnsignedByte in interface DataInput
Returns:
the next byte of this file, interpreted as an unsigned 8-bit number.
Throws:
EOFException - if this file has reached the end.
IOException - if an I/O error occurs.

readShort

public final short readShort()
                      throws IOException
Reads a signed 16-bit number from this file. The method reads 2 bytes from this file. If the two bytes read, in order, are b1 and b2, where each of the two values is between 0 and 255, inclusive, then the result is equal to:

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readShort in interface DataInput
Returns:
the next two bytes of this file, interpreted as a signed 16-bit number.
Throws:
EOFException - if this file reaches the end before reading two bytes.
IOException - if an I/O error occurs.

readShort

public final void readShort(short[] pa,
                            int start,
                            int n)
                     throws IOException
Read an array of shorts

Parameters:
pa - read into this array
start - starting at pa[start]
n - read this many elements
Throws:
IOException - on read error

readUnsignedShort

public final int readUnsignedShort()
                            throws IOException
Reads an unsigned 16-bit number from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readUnsignedShort in interface DataInput
Returns:
the next two bytes of this file, interpreted as an unsigned 16-bit integer.
Throws:
EOFException - if this file reaches the end before reading two bytes.
IOException - if an I/O error occurs.

readChar

public final char readChar()
                    throws IOException
Reads a Unicode character from this file. This method reads two bytes from the file. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

This method blocks until the two bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readChar in interface DataInput
Returns:
the next two bytes of this file as a Unicode character.
Throws:
EOFException - if this file reaches the end before reading two bytes.
IOException - if an I/O error occurs.

readInt

public final int readInt()
                  throws IOException
Reads a signed 32-bit integer from this file. This method reads 4 bytes from the file. If the bytes read, in order, are b1, b2, b3, and b4, where 0 <= b1, b2, b3, b4 <= 255, then the result is equal to:

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readInt in interface DataInput
Returns:
the next four bytes of this file, interpreted as an int.
Throws:
EOFException - if this file reaches the end before reading four bytes.
IOException - if an I/O error occurs.

readIntUnbuffered

public final int readIntUnbuffered(long pos)
                            throws IOException
Read an integer at the given position, bypassing all buffering.

Parameters:
pos - read a byte at this position
Returns:
The int that was read
Throws:
IOException - if an I/O error occurs.

readInt

public final void readInt(int[] pa,
                          int start,
                          int n)
                   throws IOException
Read an array of ints

Parameters:
pa - read into this array
start - starting at pa[start]
n - read this many elements
Throws:
IOException - on read error

readLong

public final long readLong()
                    throws IOException
Reads a signed 64-bit integer from this file. This method reads eight bytes from the file. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, where:

then the result is equal to:

     ((long)b1 << 56) + ((long)b2 << 48)
     + ((long)b3 << 40) + ((long)b4 << 32)
     + ((long)b5 << 24) + ((long)b6 << 16)
     + ((long)b7 << 8) + b8
 

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readLong in interface DataInput
Returns:
the next eight bytes of this file, interpreted as a long.
Throws:
EOFException - if this file reaches the end before reading eight bytes.
IOException - if an I/O error occurs.

readLong

public final void readLong(long[] pa,
                           int start,
                           int n)
                    throws IOException
Read an array of longs

Parameters:
pa - read into this array
start - starting at pa[start]
n - read this many elements
Throws:
IOException - on read error

readFloat

public final float readFloat()
                      throws IOException
Reads a float from this file. This method reads an int value as if by the readInt method and then converts that int to a float using the intBitsToFloat method in class Float.

This method blocks until the four bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readFloat in interface DataInput
Returns:
the next four bytes of this file, interpreted as a float.
Throws:
EOFException - if this file reaches the end before reading four bytes.
IOException - if an I/O error occurs.
See Also:
RandomAccessFile.readInt(), Float.intBitsToFloat(int)

readFloat

public final void readFloat(float[] pa,
                            int start,
                            int n)
                     throws IOException
Read an array of floats

Parameters:
pa - read into this array
start - starting at pa[start]
n - read this many elements
Throws:
IOException - on read error

readDouble

public final double readDouble()
                        throws IOException
Reads a double from this file. This method reads a long value as if by the readLong method and then converts that long to a double using the longBitsToDouble method in class Double.

This method blocks until the eight bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readDouble in interface DataInput
Returns:
the next eight bytes of this file, interpreted as a double.
Throws:
EOFException - if this file reaches the end before reading eight bytes.
IOException - if an I/O error occurs.
See Also:
RandomAccessFile.readLong(), Double.longBitsToDouble(long)

readDouble

public final void readDouble(double[] pa,
                             int start,
                             int n)
                      throws IOException
Read an array of doubles

Parameters:
pa - read into this array
start - starting at pa[start]
n - read this many elements
Throws:
IOException - on read error

readLine

public final String readLine()
                      throws IOException
Reads the next line of text from this file. This method successively reads bytes from the file until it reaches the end of a line of text.

A line of text is terminated by a carriage-return character ('\r'), a newline character ('\n'), a carriage-return character immediately followed by a newline character, or the end of the input stream. The line-terminating character(s), if any, are included as part of the string returned.

This method blocks until a newline character is read, a carriage return and the byte following it are read (to see if it is a newline), the end of the stream is detected, or an exception is thrown.

Specified by:
readLine in interface DataInput
Returns:
the next line of text from this file.
Throws:
IOException - if an I/O error occurs.

readUTF

public final String readUTF()
                     throws IOException
Reads in a string from this file. The string has been encoded using a modified UTF-8 format.

The first two bytes are read as if by readUnsignedShort. This value gives the number of following bytes that are in the encoded string, not the length of the resulting string. The following bytes are then interpreted as bytes encoding characters in the UTF-8 format and are converted into characters.

This method blocks until all the bytes are read, the end of the stream is detected, or an exception is thrown.

Specified by:
readUTF in interface DataInput
Returns:
a Unicode string.
Throws:
EOFException - if this file reaches the end before reading all the bytes.
IOException - if an I/O error occurs.
UTFDataFormatException - if the bytes do not represent valid UTF-8 encoding of a Unicode string.
See Also:
RandomAccessFile.readUnsignedShort()

readString

public String readString(int nbytes)
                  throws IOException
Read a String of knoen length.

Parameters:
nbytes - number of bytes to read
Returns:
String wrapping the bytes.
Throws:
IOException - if an I/O error occurs.

writeBoolean

public final void writeBoolean(boolean v)
                        throws IOException
Writes a boolean to the file as a 1-byte value. The value true is written out as the value (byte)1; the value false is written out as the value (byte)0.

Specified by:
writeBoolean in interface DataOutput
Parameters:
v - a boolean value to be written.
Throws:
IOException - if an I/O error occurs.

writeBoolean

public final void writeBoolean(boolean[] pa,
                               int start,
                               int n)
                        throws IOException
Write an array of booleans

Parameters:
pa - write from this array
start - starting with this element in the array
n - write this number of elements
Throws:
IOException - on read error

writeByte

public final void writeByte(int v)
                     throws IOException
Writes a byte to the file as a 1-byte value.

Specified by:
writeByte in interface DataOutput
Parameters:
v - a byte value to be written.
Throws:
IOException - if an I/O error occurs.

writeShort

public final void writeShort(int v)
                      throws IOException
Writes a short to the file as two bytes, high byte first.

Specified by:
writeShort in interface DataOutput
Parameters:
v - a short to be written.
Throws:
IOException - if an I/O error occurs.

writeShort

public final void writeShort(short[] pa,
                             int start,
                             int n)
                      throws IOException
Write an array of shorts

Parameters:
pa - write from this array
start - starting with this element in the array
n - this number of elements
Throws:
IOException - on read error

writeChar

public final void writeChar(int v)
                     throws IOException
Writes a char to the file as a 2-byte value, high byte first.

Specified by:
writeChar in interface DataOutput
Parameters:
v - a char value to be written.
Throws:
IOException - if an I/O error occurs.

writeChar

public final void writeChar(char[] pa,
                            int start,
                            int n)
                     throws IOException
Write an array of chars

Parameters:
pa - write from this array
start - starting with this element in the array
n - this number of elements
Throws:
IOException - on read error

writeInt

public final void writeInt(int v)
                    throws IOException
Writes an int to the file as four bytes, high byte first.

Specified by:
writeInt in interface DataOutput
Parameters:
v - an int to be written.
Throws:
IOException - if an I/O error occurs.

writeInt

public final void writeInt(int[] pa,
                           int start,
                           int n)
                    throws IOException
Write an array of ints

Parameters:
pa - write from this array
start - starting with this element in the array
n - write this number of elements
Throws:
IOException - on read error

writeLong

public final void writeLong(long v)
                     throws IOException
Writes a long to the file as eight bytes, high byte first.

Specified by:
writeLong in interface DataOutput
Parameters:
v - a long to be written.
Throws:
IOException - if an I/O error occurs.

writeLong

public final void writeLong(long[] pa,
                            int start,
                            int n)
                     throws IOException
Write an array of longs

Parameters:
pa - write from this array
start - starting with this element in the array
n - write this number of elements
Throws:
IOException - on read error

writeFloat

public final void writeFloat(float v)
                      throws IOException
Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the file as a 4-byte quantity, high byte first.

Specified by:
writeFloat in interface DataOutput
Parameters:
v - a float value to be written.
Throws:
IOException - if an I/O error occurs.
See Also:
Float.floatToIntBits(float)

writeFloat

public final void writeFloat(float[] pa,
                             int start,
                             int n)
                      throws IOException
Write an array of floats

Parameters:
pa - write from this array
start - starting with this element in the array
n - write this number of elements
Throws:
IOException - on read error

writeDouble

public final void writeDouble(double v)
                       throws IOException
Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the file as an 8-byte quantity, high byte first.

Specified by:
writeDouble in interface DataOutput
Parameters:
v - a double value to be written.
Throws:
IOException - if an I/O error occurs.
See Also:
Double.doubleToLongBits(double)

writeDouble

public final void writeDouble(double[] pa,
                              int start,
                              int n)
                       throws IOException
Write an array of doubles

Parameters:
pa - write from this array
start - starting with this element in the array
n - write this number of elements
Throws:
IOException - on read error

writeBytes

public final void writeBytes(String s)
                      throws IOException
Writes the string to the file as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits.

Specified by:
writeBytes in interface DataOutput
Parameters:
s - a string of bytes to be written.
Throws:
IOException - if an I/O error occurs.

writeBytes

public final void writeBytes(char[] b,
                             int off,
                             int len)
                      throws IOException
Writes the character array to the file as a sequence of bytes. Each character in the string is written out, in sequence, by discarding its high eight bits.

Parameters:
b - a character array of bytes to be written.
off - the index of the first character to write.
len - the number of characters to write.
Throws:
IOException - if an I/O error occurs.

writeChars

public final void writeChars(String s)
                      throws IOException
Writes a string to the file as a sequence of characters. Each character is written to the data output stream as if by the writeChar method.

Specified by:
writeChars in interface DataOutput
Parameters:
s - a String value to be written.
Throws:
IOException - if an I/O error occurs.
See Also:
RandomAccessFile.writeChar(int)

writeUTF

public final void writeUTF(String str)
                    throws IOException
Writes a string to the file using UTF-8 encoding in a machine-independent manner.

First, two bytes are written to the file as if by the writeShort method giving the number of bytes to follow. This value is the number of bytes actually written out, not the length of the string. Following the length, each character of the string is output, in sequence, using the UTF-8 encoding for each character.

Specified by:
writeUTF in interface DataOutput
Parameters:
str - a string to be written.
Throws:
IOException - if an I/O error occurs.

toString

public String toString()
Create a string representation of this object.

Overrides:
toString in class Object
Returns:
a string representation of the state of the object.

searchForward

public boolean searchForward(KMPMatch match,
                             int maxBytes)
                      throws IOException
Search forward from the current pos, looking for a match.

Parameters:
match - the match to look for.
maxBytes - maximum number of bytes to search. use -1 for all
Returns:
true if found, file position will be at the start of the match.
Throws:
IOException - on read error


Copyright © 1999-2011 UCAR/Unidata. All Rights Reserved.