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org.apache.batik.ext.awt.image.codec
Class SeekableStream  

java.lang.Object
  java.io.InputStream
      org.apache.batik.ext.awt.image.codec.SeekableStream

All Implemented Interfaces:

java.io.Closeable, java.io.DataInput

Direct Known Subclasses:

FileCacheSeekableStream, ForwardSeekableStream, MemoryCacheSeekableStream

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public abstract class SeekableStream

extends java.io.InputStream

implements java.io.DataInput

An abstract subclass of java.io.InputStream that allows seeking within the input, similar to the RandomAccessFile class. Additionally, the DataInput interface is supported and extended to include support for little-endian representations of fundamental data types.

In addition to the familiar methods from InputStream, the methods getFilePointer(), seek(), are defined as in the RandomAccessFile class. The canSeekBackwards() method will return true if it is permissible to seek to a position earlier in the stream than the current value of getFilePointer(). Some subclasses of SeekableStream guarantee the ability to seek backwards while others may not offer this feature in the interest of providing greater efficiency for those users who do not require it.

The DataInput interface is supported as well. This included the skipBytes() and readFully() methods and a variety of read methods for various data types.

A number of concrete subclasses of SeekableStream are supplied in the com.sun.media.jai.codec package.

Three classes are provided for the purpose of adapting a standard InputStream to the SeekableStream interface. ForwardSeekableStream does not allows seeking backwards, but is inexpensive to use. FileCacheSeekableStream maintains a copy of all of the data read from the input in a temporary file; this file will be discarded automatically when the FileSeekableStream is finalized, or when the JVM exits normally. FileCacheSeekableStream is intended to be reasonably efficient apart from the unavoidable use of disk space. In circumstances where the creation of a temporary file is not possible, MemoryCacheSeekableStream may be used. MemoryCacheSeekableStream creates a potentially large in-memory buffer to store the stream data and so should be avoided when possible.

The FileSeekableStream class wraps a File or RandomAccessFile. It forwards requests to the real underlying file. It performs a limited amount of caching in order to avoid excessive I/O costs.

The SegmentedSeekableStream class performs a different sort of function. It creates a SeekableStream from another SeekableStream by selecting a series of portions or "segments". Each segment starts at a specified location within the source SeekableStream and extends for a specified number of bytes. The StreamSegmentMapper interface and StreamSegment class may be used to compute the segment positions dynamically.

A convenience methods, wrapInputStream is provided to construct a suitable SeekableStream instance whose data is supplied by a given InputStream. The caller, by means of the canSeekBackwards parameter, determines whether support for seeking backwards is required.

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Field Summary
protected  long	markPos           Marked position
private  byte[]	ruileBuf

 

Constructor Summary

SeekableStream()

 

Method Summary
boolean	canSeekBackwards()           Returns true if this object supports calls to seek(pos) with an offset pos smaller than the current offset, as returned by getFilePointer.
protected  void	finalize()           Releases any system resources associated with this stream by calling the close() method.
abstract  long	getFilePointer()           Returns the current offset in this stream.
void	mark(int readLimit)           Marks the current file position for later return using the reset() method.
boolean	markSupported()           Returns true if marking is supported.
abstract  int	read()           Reads the next byte of data from the input stream.
abstract  int	read(byte[] b, int off, int len)           Reads up to len bytes of data from the input stream into an array of bytes.
boolean	readBoolean()           Reads a boolean from this stream.
byte	readByte()           Reads a signed eight-bit value from this stream.
char	readChar()           Reads a Unicode character from this stream.
char	readCharLE()           Reads a Unicode character from this stream in little-endian order.
double	readDouble()           Reads a double from this stream.
double	readDoubleLE()           Reads a double from this stream in little-endian order.
float	readFloat()           Reads a float from this stream.
float	readFloatLE()           Reads a float from this stream in little-endian order.
void	readFully(byte[] b)           Reads b.length bytes from this stream into the byte array, starting at the current stream pointer.
void	readFully(byte[] b, int off, int len)           Reads exactly len bytes from this stream into the byte array, starting at the current stream pointer.
int	readInt()           Reads a signed 32-bit integer from this stream.
int	readIntLE()           Reads a signed 32-bit integer from this stream in little-endian order.
java.lang.String	readLine()           Reads the next line of text from this stream.
long	readLong()           Reads a signed 64-bit integer from this stream.
long	readLongLE()           Reads a signed 64-bit integer from this stream in little-endian order.
short	readShort()           Reads a signed 16-bit number from this stream.
short	readShortLE()           Reads a signed 16-bit number from this stream in little-endian order.
int	readUnsignedByte()           Reads an unsigned eight-bit number from this stream.
long	readUnsignedInt()           Reads an unsigned 32-bit integer from this stream.
long	readUnsignedIntLE()           Reads an unsigned 32-bit integer from this stream in little-endian order.
int	readUnsignedShort()           Reads an unsigned 16-bit number from this stream.
int	readUnsignedShortLE()           Reads an unsigned 16-bit number from this stream in little-endian order.
java.lang.String	readUTF()           Reads in a string from this stream.
void	reset()           Returns the file position to its position at the time of the immediately previous call to the mark() method.
abstract  void	seek(long pos)           Sets the offset, measured from the beginning of this stream, at which the next read occurs.
int	skipBytes(int n)           Attempts to skip over n bytes of input discarding the skipped bytes.
static SeekableStream	wrapInputStream(java.io.InputStream is, boolean canSeekBackwards)           Returns a SeekableStream that will read from a given InputStream, optionally including support for seeking backwards.

 

Methods inherited from class java.io.InputStream

available, close, read, skip

 

Methods inherited from class java.lang.Object

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

 

Field Detail

markPos

protected long markPos

Marked position

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ruileBuf

private byte[] ruileBuf

Constructor Detail

SeekableStream

public SeekableStream()

Method Detail

wrapInputStream

public static SeekableStream wrapInputStream(java.io.InputStream is,
                                             boolean canSeekBackwards)

Returns a SeekableStream that will read from a given InputStream, optionally including support for seeking backwards. This is a convenience method that avoids the need to instantiate specific subclasses of SeekableStream depending on the current security model.

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read

public abstract int read()
                  throws java.io.IOException

Reads the next byte of data from the input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown.

A subclass must provide an implementation of this method.

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read

public abstract int read(byte[] b,
                         int off,
                         int len)
                  throws java.io.IOException

Reads up to len bytes of data from the input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read, possibly zero. The number of bytes actually read is returned as an integer.

This method blocks until input data is available, end of stream is detected, or an exception is thrown.

If b is null, a NullPointerException is thrown.

If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown.

If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of stream, the value -1 is returned; otherwise, at least one byte is read and stored into b.

The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected.

In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected.

If the first byte cannot be read for any reason other than end of stream, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed.

A subclass must provide an implementation of this method.

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mark

public void mark(int readLimit)

Marks the current file position for later return using the reset() method.

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reset

public void reset()
           throws java.io.IOException

Returns the file position to its position at the time of the immediately previous call to the mark() method.

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markSupported

public boolean markSupported()

Returns true if marking is supported. Marking is automatically supported for SeekableStream subclasses that support seeking backeards. Subclasses that do not support seeking backwards but do support marking must override this method.

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canSeekBackwards

public boolean canSeekBackwards()

Returns true if this object supports calls to seek(pos) with an offset pos smaller than the current offset, as returned by getFilePointer.

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getFilePointer

public abstract long getFilePointer()
                             throws java.io.IOException

Returns the current offset in this stream.

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seek

public abstract void seek(long pos)
                   throws java.io.IOException

Sets the offset, measured from the beginning of this stream, at which the next read occurs.

If canSeekBackwards() returns false, then setting pos to an offset smaller than the current value of getFilePointer() will have no effect.

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readFully

public final void readFully(byte[] b)
                     throws java.io.IOException

Reads b.length bytes from this stream into the byte array, starting at the current stream pointer. This method reads repeatedly from the stream 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.

Specified by:

readFully in interface java.io.DataInput

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readFully

public final void readFully(byte[] b,
                            int off,
                            int len)
                     throws java.io.IOException

Reads exactly len bytes from this stream into the byte array, starting at the current stream pointer. This method reads repeatedly from the stream 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.

Specified by:

readFully in interface java.io.DataInput

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skipBytes

public int skipBytes(int n)
              throws java.io.IOException

Attempts to skip over n 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 stream before n bytes have been skipped is only one possibility. This method never throws an EOFException. The actual number of bytes skipped is returned. If n is negative, no bytes are skipped.

Specified by:

skipBytes in interface java.io.DataInput

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readBoolean

public final boolean readBoolean()
                          throws java.io.IOException

Reads a boolean from this stream. This method reads a single byte from the stream, starting at the current stream pointer. 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 java.io.DataInput

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readByte

public final byte readByte()
                    throws java.io.IOException

Reads a signed eight-bit value from this stream. This method reads a byte from the stream, starting from the current stream pointer. If the byte read is b, where 0 <= b <= 255, then the result is:

     (byte)(b)
 

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 java.io.DataInput

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readUnsignedByte

public final int readUnsignedByte()
                           throws java.io.IOException

Reads an unsigned eight-bit number from this stream. This method reads a byte from this stream, starting at the current stream pointer, 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 java.io.DataInput

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readShort

public final short readShort()
                      throws java.io.IOException

Reads a signed 16-bit number from this stream. The method reads two bytes from this stream, starting at the current stream pointer. 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:

     (short)((b1 << 8) | b2)
 

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 java.io.DataInput

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readShortLE

public final short readShortLE()
                        throws java.io.IOException

Reads a signed 16-bit number from this stream in little-endian order. The method reads two bytes from this stream, starting at the current stream pointer. 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:

     (short)((b2 << 8) | b1)
 

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

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readUnsignedShort

public final int readUnsignedShort()
                            throws java.io.IOException

Reads an unsigned 16-bit number from this stream. This method reads two bytes from the stream, starting at the current stream pointer. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

     (b1 << 8) | b2
 

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 java.io.DataInput

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readUnsignedShortLE

public final int readUnsignedShortLE()
                              throws java.io.IOException

Reads an unsigned 16-bit number from this stream in little-endian order. This method reads two bytes from the stream, starting at the current stream pointer. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

     (b2 << 8) | b1
 

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

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readChar

public final char readChar()
                    throws java.io.IOException

Reads a Unicode character from this stream. This method reads two bytes from the stream, starting at the current stream pointer. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

     (char)((b1 << 8) | b2)
 

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 java.io.DataInput

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readCharLE

public final char readCharLE()
                      throws java.io.IOException

Reads a Unicode character from this stream in little-endian order. This method reads two bytes from the stream, starting at the current stream pointer. If the bytes read, in order, are b1 and b2, where 0 <= b1, b2 <= 255, then the result is equal to:

     (char)((b2 << 8) | b1)
 

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

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readInt

public final int readInt()
                  throws java.io.IOException

Reads a signed 32-bit integer from this stream. This method reads 4 bytes from the stream, starting at the current stream pointer. 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:

     (b1 << 24) | (b2 << 16) + (b3 << 8) + b4
 

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 java.io.DataInput

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readIntLE

public final int readIntLE()
                    throws java.io.IOException

Reads a signed 32-bit integer from this stream in little-endian order. This method reads 4 bytes from the stream, starting at the current stream pointer. 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:

     (b4 << 24) | (b3 << 16) + (b2 << 8) + b1
 

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

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readUnsignedInt

public final long readUnsignedInt()
                           throws java.io.IOException

Reads an unsigned 32-bit integer from this stream. This method reads 4 bytes from the stream, starting at the current stream pointer. 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:

     (b1 << 24) | (b2 << 16) + (b3 << 8) + b4
 

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

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readUnsignedIntLE

public final long readUnsignedIntLE()
                             throws java.io.IOException

Reads an unsigned 32-bit integer from this stream in little-endian order. This method reads 4 bytes from the stream, starting at the current stream pointer. 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:

     (b4 << 24) | (b3 << 16) + (b2 << 8) + b1
 

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

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readLong

public final long readLong()
                    throws java.io.IOException

Reads a signed 64-bit integer from this stream. This method reads eight bytes from the stream, starting at the current stream pointer. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, where:

     0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
 

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 java.io.DataInput

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readLongLE

public final long readLongLE()
                      throws java.io.IOException

Reads a signed 64-bit integer from this stream in little-endian order. This method reads eight bytes from the stream, starting at the current stream pointer. If the bytes read, in order, are b1, b2, b3, b4, b5, b6, b7, and b8, where:

     0 <= b1, b2, b3, b4, b5, b6, b7, b8 <=255,
 

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.

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readFloat

public final float readFloat()
                      throws java.io.IOException

Reads a float from this stream. This method reads an int value, starting at the current stream pointer, 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 java.io.DataInput

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readFloatLE

public final float readFloatLE()
                        throws java.io.IOException

Reads a float from this stream in little-endian order. This method reads an int value, starting at the current stream pointer, 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.

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readDouble

public final double readDouble()
                        throws java.io.IOException

Reads a double from this stream. This method reads a long value, starting at the current stream pointer, 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 java.io.DataInput

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readDoubleLE

public final double readDoubleLE()
                          throws java.io.IOException

Reads a double from this stream in little-endian order. This method reads a long value, starting at the current stream pointer, 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.

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readLine

public final java.lang.String readLine()
                                throws java.io.IOException

Reads the next line of text from this stream. This method successively reads bytes from the stream, starting at the current stream pointer, until it reaches a line terminator or the end of the stream. Each byte is converted into a character by taking the byte's value for the lower eight bits of the character and setting the high eight bits of the character to zero. This method does not, therefore, support the full Unicode character set.

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 stream. Line-terminating characters are discarded and are not 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 reached, or an exception is thrown.

Specified by:

readLine in interface java.io.DataInput

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readUTF

public final java.lang.String readUTF()
                               throws java.io.IOException

Reads in a string from this stream. The string has been encoded using a modified UTF-8 format.

The first two bytes are read, starting from the current stream pointer, 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 java.io.DataInput

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finalize

protected void finalize()
                 throws java.lang.Throwable

Releases any system resources associated with this stream by calling the close() method.

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Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> batik >> ext >> awt >> image >> [ codec overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

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