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java.lang.Object
|
+--java.io.InputStream
|
+--com.sun.media.jai.codec.SeekableStream
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 FileCacheSeekableStream 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.
DataInput,
InputStream,
RandomAccessFile,
ByteArraySeekableStream,
FileCacheSeekableStream,
FileSeekableStream,
ForwardSeekableStream,
MemoryCacheSeekableStream,
SegmentedSeekableStream,
StreamSegment,
This class is not a committed part of the JAI API. It may
be removed or changed in future releases of JAI.
| Field Summary | |
protected long |
markPos
Marked position |
| 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. |
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. |
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(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 |
protected long markPos
| Constructor Detail |
public SeekableStream()
| Method Detail |
public static SeekableStream wrapInputStream(InputStream is,
boolean canSeekBackwards)
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.is - An InputStream.canSeekBackwards - true if the ability to seek
backwards in the output is required.SeekableStream.
public abstract int read()
throws IOException
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.
-1 if the end of the
stream is reached.
public abstract int read(byte[] b,
int off,
int len)
throws IOException
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.
b - the buffer into which the data is read.off - the start offset in array b
at which the data is written.len - the maximum number of bytes to read.-1 if there is no more data because the end of
the stream has been reached.public void mark(int readLimit)
reset() method.
public void reset()
throws IOException
mark()
method.public boolean markSupported()
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.public boolean canSeekBackwards()
true if this object supports calls to
seek(pos) with an offset pos smaller
than the current offset, as returned by getFilePointer.
public abstract long getFilePointer()
throws IOException
public abstract void seek(long pos)
throws IOException
If canSeekBackwards() returns false,
then setting pos to an offset smaller than
the current value of getFilePointer() will have
no effect.
pos - the offset position, measured in bytes from the
beginning of the stream, at which to set the stream
pointer.pos is less than
0 or if an I/O error occurs.
public final void readFully(byte[] b)
throws IOException
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.b - the buffer into which the data is read.
public final void readFully(byte[] b,
int off,
int len)
throws IOException
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.b - the buffer into which the data is read.off - the start offset of the data.len - the number of bytes to read.
public int skipBytes(int n)
throws IOException
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.
n - the number of bytes to be skipped.
public final boolean readBoolean()
throws IOException
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.boolean value read.
public final byte readByte()
throws IOException
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.
byte.
public final int readUnsignedByte()
throws IOException
This method blocks until the byte is read, the end of the stream is detected, or an exception is thrown.
public final short readShort()
throws IOException
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.
public final short readShortLE()
throws IOException
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.
public final int readUnsignedShort()
throws IOException
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.
public final int readUnsignedShortLE()
throws IOException
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.
public final char readChar()
throws IOException
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.
public final char readCharLE()
throws IOException
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.
public final int readInt()
throws IOException
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.
int.
public final int readIntLE()
throws IOException
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.
int.
public final long readUnsignedInt()
throws IOException
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.
long.
public final long readUnsignedIntLE()
throws IOException
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.
long.
public final long readLong()
throws IOException
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.
long.
public final long readLongLE()
throws IOException
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.
long.
public final float readFloat()
throws IOException
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.
float.
public final float readFloatLE()
throws IOException
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.
float.
public final double readDouble()
throws IOException
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.
double.
public final double readDoubleLE()
throws IOException
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.
double.
public final String readLine()
throws IOException
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.
public final String readUTF()
throws IOException
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.
protected void finalize()
throws Throwable
close() method.
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