Module java.desktop

Class ImageInputStreamImpl

java.lang.Object
javax.imageio.stream.ImageInputStreamImpl
All Implemented Interfaces:
Closeable, DataInput, AutoCloseable, ImageInputStream
Direct Known Subclasses:
FileCacheImageInputStream, FileImageInputStream, ImageOutputStreamImpl, MemoryCacheImageInputStream

public abstract class ImageInputStreamImpl
extends Object
implements ImageInputStream
An abstract class implementing the ImageInputStream interface. This class is designed to reduce the number of methods that must be implemented by subclasses.

In particular, this class handles most or all of the details of byte order interpretation, buffering, mark/reset, discarding, closing, and disposing.

  • Field Details

    • byteOrder

      protected ByteOrder byteOrder
      The byte order of the stream as an instance of the enumeration class java.nio.ByteOrder, where ByteOrder.BIG_ENDIAN indicates network byte order and ByteOrder.LITTLE_ENDIAN indicates the reverse order. By default, the value is ByteOrder.BIG_ENDIAN.
    • streamPos

      protected long streamPos
      The current read position within the stream. Subclasses are responsible for keeping this value current from any method they override that alters the read position.
    • bitOffset

      protected int bitOffset
      The current bit offset within the stream. Subclasses are responsible for keeping this value current from any method they override that alters the bit offset.
    • flushedPos

      protected long flushedPos
      The position prior to which data may be discarded. Seeking to a smaller position is not allowed. flushedPos will always be >= 0.
  • Constructor Details

    • ImageInputStreamImpl

      public ImageInputStreamImpl()
      Constructs an ImageInputStreamImpl.
  • Method Details

    • checkClosed

      protected final void checkClosed() throws IOException
      Throws an IOException if the stream has been closed. Subclasses may call this method from any of their methods that require the stream not to be closed.
      Throws:
      IOException - if the stream is closed.
    • read

      public abstract int read() throws IOException
      Reads a single byte from the stream and returns it as an int between 0 and 255. If EOF is reached, -1 is returned.

      Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.

      The bit offset within the stream must be reset to zero before the read occurs.

      Specified by:
      read in interface ImageInputStream
      Returns:
      the value of the next byte in the stream, or -1 if EOF is reached.
      Throws:
      IOException - if the stream has been closed.
    • read

      public int read​(byte[] b) throws IOException
      A convenience method that calls read(b, 0, b.length).

      The bit offset within the stream is reset to zero before the read occurs.

      Specified by:
      read in interface ImageInputStream
      Parameters:
      b - an array of bytes to be written to.
      Returns:
      the number of bytes actually read, or -1 to indicate EOF.
      Throws:
      NullPointerException - if b is null.
      IOException - if an I/O error occurs.
    • read

      public abstract int read​(byte[] b, int off, int len) throws IOException
      Reads up to len bytes from the stream, and stores them into b starting at index off. If no bytes can be read because the end of the stream has been reached, -1 is returned.

      The bit offset within the stream must be reset to zero before the read occurs.

      Subclasses must provide an implementation for this method. The subclass implementation should update the stream position before exiting.

      Specified by:
      read in interface ImageInputStream
      Parameters:
      b - an array of bytes to be written to.
      off - the starting position within b to write to.
      len - the maximum number of bytes to read.
      Returns:
      the number of bytes actually read, or -1 to indicate EOF.
      Throws:
      IndexOutOfBoundsException - if off is negative, len is negative, or off + len is greater than b.length.
      NullPointerException - if b is null.
      IOException - if an I/O error occurs.
    • length

      public long length()
      Returns -1L to indicate that the stream has unknown length. Subclasses must override this method to provide actual length information.
      Specified by:
      length in interface ImageInputStream
      Returns:
      -1L to indicate unknown length.
    • skipBytes

      public int skipBytes​(int n) throws IOException
      Advances the current stream position by calling seek(getStreamPosition() + n).

      The bit offset is reset to zero.

      Specified by:
      skipBytes in interface DataInput
      Specified by:
      skipBytes in interface ImageInputStream
      Parameters:
      n - the number of bytes to seek forward.
      Returns:
      an int representing the number of bytes skipped.
      Throws:
      IOException - if getStreamPosition throws an IOException when computing either the starting or ending position.
    • skipBytes

      public long skipBytes​(long n) throws IOException
      Advances the current stream position by calling seek(getStreamPosition() + n).

      The bit offset is reset to zero.

      Specified by:
      skipBytes in interface ImageInputStream
      Parameters:
      n - the number of bytes to seek forward.
      Returns:
      a long representing the number of bytes skipped.
      Throws:
      IOException - if getStreamPosition throws an IOException when computing either the starting or ending position.
    • mark

      public void mark()
      Pushes the current stream position onto a stack of marked positions.
      Specified by:
      mark in interface ImageInputStream
    • reset

      public void reset() throws IOException
      Resets the current stream byte and bit positions from the stack of marked positions.

      An IOException will be thrown if the previous marked position lies in the discarded portion of the stream.

      Specified by:
      reset in interface ImageInputStream
      Throws:
      IOException - if an I/O error occurs.
    • isCached

      public boolean isCached()
      Default implementation returns false. Subclasses should override this if they cache data.
      Specified by:
      isCached in interface ImageInputStream
      Returns:
      true if this ImageInputStream caches data.
      See Also:
      ImageInputStream.isCachedMemory(), ImageInputStream.isCachedFile()
    • isCachedMemory

      public boolean isCachedMemory()
      Default implementation returns false. Subclasses should override this if they cache data in main memory.
      Specified by:
      isCachedMemory in interface ImageInputStream
      Returns:
      true if this ImageInputStream caches data in main memory.
      See Also:
      ImageInputStream.isCached(), ImageInputStream.isCachedFile()
    • isCachedFile

      public boolean isCachedFile()
      Default implementation returns false. Subclasses should override this if they cache data in a temporary file.
      Specified by:
      isCachedFile in interface ImageInputStream
      Returns:
      true if this ImageInputStream caches data in a temporary file.
      See Also:
      ImageInputStream.isCached(), ImageInputStream.isCachedMemory()
    • finalize

      @Deprecated(since="9") protected void finalize() throws Throwable
      Deprecated.
      The finalize method has been deprecated. Subclasses that override finalize in order to perform cleanup should be modified to use alternative cleanup mechanisms and to remove the overriding finalize method. When overriding the finalize method, its implementation must explicitly ensure that super.finalize() is invoked as described in Object.finalize(). See the specification for Object.finalize() for further information about migration options.
      Finalizes this object prior to garbage collection. The close method is called to close any open input source. This method should not be called from application code.
      Overrides:
      finalize in class Object
      Throws:
      Throwable - if an error occurs during superclass finalization.
      See Also:
      WeakReference, PhantomReference