com.pixelmed.dicom
Class EncapsulatedInputStream

java.lang.Object
  java.io.InputStream
      com.pixelmed.dicom.EncapsulatedInputStream

All Implemented Interfaces:

Closeable

public class EncapsulatedInputStream
extends InputStream

A class that extends InputStream by adding a mechanism for unecapsulating an undefined length DICOM attribute, such as is used for compressed Pixel Data.

The read methods hide the fact that the data is encapsulated by removing the Items and Item and Sequence delimiter tags, as well as skipping any Basic Offset Table that may be present in the first Item.

Since an individual frame may be fragmented and padded woth 0xff bytes beyond the JPEG EOI marker (0xffd9), and since the codec used for decoding may be "reading ahead" this class also removes any padding 0xff bytes at the end of any fragment, back as far as the EOI marker. Note that this means that theorectically frames could span fragments as long as there was no padding between them.

Constructor Summary

EncapsulatedInputStream(BinaryInputStream i)
Construct a byte ordered stream from the supplied stream.

Method Summary

protected long	getBytesRead()
void	nextFrame() Skip to the start of a fragment, if not already there.
int	read() Extracts the next byte of data from the current or subsequent fragments.
int	read(byte[] b) Extracts byte.length bytes of data from the current or subsequent fragments.
int	read(byte[] b, int off, int len) Extracts len bytes of data from the current or subsequent fragments.
void	readSequenceDelimiter()
void	readUnsigned16(short[] w, int offset, int len) Read an array of unsigned integer 16 bit values.

Methods inherited from class java.io.InputStream

available, close, mark, markSupported, reset, skip

Methods inherited from class java.lang.Object

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

Constructor Detail

EncapsulatedInputStream

public EncapsulatedInputStream(BinaryInputStream i)

Construct a byte ordered stream from the supplied stream.

The byte order may be changed later.

Parameters:

i - the input stream to read from

Method Detail

getBytesRead

protected long getBytesRead()

readSequenceDelimiter

public void readSequenceDelimiter()
                           throws IOException

Throws:

IOException

nextFrame

public void nextFrame()

Skip to the start of a fragment, if not already there.

readUnsigned16

public final void readUnsigned16(short[] w,
                                 int offset,
                                 int len)
                          throws IOException

Read an array of unsigned integer 16 bit values.

Parameters:

w - an array of sufficient size in which to return the values read

offset - the offset in the array at which to begin storing values

len - the number of 16 bit values to read

Throws:

IOException

read

public final int read()
               throws IOException

Extracts the next byte of data from the current or subsequent fragments.

Specified by:

read in class InputStream

Returns:

the next byte of data, or -1 if there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

read

public final int read(byte[] b)
               throws IOException

Extracts byte.length bytes of data from the current or subsequent fragments.

This method simply performs the call read(b, 0, b.length) and returns the result.

Overrides:

read in class InputStream

Parameters:

b - the buffer into which the data is read.

Returns:

the total number of bytes read into the buffer (always whatever was asked for), or -1 if there is no more data because the end of the stream has been reached.

Throws:

IOException - if an I/O error occurs.

See Also:

read(byte[], int, int)

read

public final int read(byte[] b,
                      int off,
                      int len)
               throws IOException

Extracts len bytes of data from the current or subsequent fragments.

Overrides:

read in class InputStream

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the number of bytes read.

Returns:

the total number of bytes read into the buffer (always whatever was asked for), or -1 if there is no more data because the end of a frame has been reached.

Throws:

IOException - if an I/O error occurs.