MemoryCacheImageInputStream (Java 2 Platform SE v1.4.1_"07")

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JavaTM 2 Platform
Std. Ed. v1.4.1_"07"

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## javax.imageio.stream
Class MemoryCacheImageInputStream

    java.lang.Object
      |
      +--javax.imageio.stream.ImageInputStreamImpl
            |
            +--javax.imageio.stream.MemoryCacheImageInputStream

All Implemented Interfaces:
  DataInput, ImageInputStream

public class MemoryCacheImageInputStream
extends ImageInputStreamImpl

An implementation of `ImageInputStream` that gets its input from a regular `InputStream`. A memory buffer is used to cache at least the data between the discard position and the current read position.

In general, it is preferable to use a `FileCacheImageInputStream` when reading from a regular `InputStream`. This class is provided for cases where it is not possible to create a writable temporary file.

Field Summary

Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
`bitOffset, byteOrder, flushedPos, streamPos`

Constructor Summary
`MemoryCacheImageInputStream(InputStream stream)` Constructs a `MemoryCacheImageInputStream` that will read from a given `InputStream`.

Method Summary
`void` | `close()` Closes this `MemoryCacheImageInputStream`, freeing the cache.
`void` | `flushBefore(long pos)` Discards the initial portion of the stream prior to the indicated postion.
`boolean` | `isCached()` Returns `true` since this `ImageInputStream` caches data in order to allow seeking backwards.
`boolean` | `isCachedFile()` Returns `false` since this `ImageInputStream` does not maintain a file cache.
`boolean` | `isCachedMemory()` Returns `true` since this `ImageInputStream` maintains a main memory cache.
`int` | `read()` Reads a single byte from the stream and returns it as an integer between 0 and 255.
`int` | `read(byte[] b, int off, int len)` Reads up to `len` bytes from the stream, and stores them into `b` starting at index `off`.

Methods inherited from class javax.imageio.stream.ImageInputStreamImpl
`checkClosed, finalize, flush, getBitOffset, getByteOrder, getFlushedPosition, getStreamPosition, length, mark, read, readBit, readBits, readBoolean, readByte, readBytes, readChar, readDouble, readFloat, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedInt, readUnsignedShort, readUTF, reset, seek, setBitOffset, setByteOrder, skipBytes, skipBytes`

Methods inherited from class java.lang.Object
`clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### MemoryCacheImageInputStream

    public MemoryCacheImageInputStream(InputStream stream)

  Constructs a `MemoryCacheImageInputStream` that will read from a given `InputStream`.

Parameters:
  `stream` - an `InputStream` to read from.
Throws:
  `IllegalArgumentException` - if `stream` is `null`.

Method Detail

### read

    public int read()
             throws IOException

  Description copied from interface: `ImageInputStream`
  Reads a single byte from the stream and returns it as an integer between 0 and 255. If the end of the stream is reached, -1 is returned.

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

  Specified by:
    `read` in interface `ImageInputStream`
  Specified by:
    `read` in class `ImageInputStreamImpl`
  Returns:
    a byte value from the stream, as an int, or -1 to indicate EOF.
  Throws:
    `IOException` - if an I/O error occurs.

### read

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

  Description copied from class: `ImageInputStreamImpl`
  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`
  Specified by:
    `read` in class `ImageInputStreamImpl`
  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:
    `IOException` - if an I/O error occurs.

### flushBefore

    public void flushBefore(long pos)
                     throws IOException

  Description copied from interface: `ImageInputStream`
  Discards the initial portion of the stream prior to the indicated postion. Attempting to seek to an offset within the flushed portion of the stream will result in an `IndexOutOfBoundsException`.

  Calling `flushBefore` may allow classes implementing this interface to free up resources such as memory or disk space that are being used to store data from the stream.

  Specified by:
    `flushBefore` in interface `ImageInputStream`
  Overrides:
    `flushBefore` in class `ImageInputStreamImpl`
  Parameters:
    `pos` - a `long` containing the length of the file prefix that may be flushed.
  Throws:
    `IOException` - if an I/O error occurs.

### isCached

    public boolean isCached()

  Returns `true` since this `ImageInputStream` caches data in order to allow seeking backwards.

  Specified by:
    `isCached` in interface `ImageInputStream`
  Overrides:
    `isCached` in class `ImageInputStreamImpl`
  Returns:
    `true`.
  See Also:
    `isCachedMemory()`, `isCachedFile()`

### isCachedFile

    public boolean isCachedFile()

  Returns `false` since this `ImageInputStream` does not maintain a file cache.

  Specified by:
    `isCachedFile` in interface `ImageInputStream`
  Overrides:
    `isCachedFile` in class `ImageInputStreamImpl`
  Returns:
    `false`.
  See Also:
    `isCached()`, `isCachedMemory()`

### isCachedMemory

    public boolean isCachedMemory()

  Returns `true` since this `ImageInputStream` maintains a main memory cache.

  Specified by:
    `isCachedMemory` in interface `ImageInputStream`
  Overrides:
    `isCachedMemory` in class `ImageInputStreamImpl`
  Returns:
    `true`.
  See Also:
    `isCached()`, `isCachedFile()`

### close

    public void close()
               throws IOException

  Closes this `MemoryCacheImageInputStream`, freeing the cache. The source `InputStream` is not closed.

  Specified by:
    `close` in interface `ImageInputStream`
  Overrides:
    `close` in class `ImageInputStreamImpl`
  Throws:
    `IOException` - if an I/O error occurs.

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JavaTM 2 Platform
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For further API reference and developer documentation, see Java 2 SDK SE Developer Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.

Copyright 2002 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.