Class MemoryCacheImageInputStream

java.lang.Object

javax.imageio.stream.ImageInputStreamImpl

javax.imageio.stream.MemoryCacheImageInputStream

All Implemented Interfaces:: Closeable, DataInput, AutoCloseable, 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 declared in class ImageInputStreamImpl

bitOffset, byteOrder, flushedPos, streamPos

Modifier and Type	Field	Description
`protected int`	`bitOffset`	The current bit offset within the stream.
`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.
`protected long`	`flushedPos`	The position prior to which data may be discarded.
`protected long`	`streamPos`	The current read position within the stream.

Constructor Summary

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

Method Summary

Modifier and Type	Method	Description
`void`	`close()`	Closes this `MemoryCacheImageInputStream`, freeing the cache.
`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 `int` 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 declared in class ImageInputStreamImpl

checkClosed, flush, flushBefore, 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

Modifier and Type	Method	Description
`protected final void`	`checkClosed()`	Throws an `IOException` if the stream has been closed.
`void`	`flush()`	Discards the initial position of the stream prior to the current stream position.
`void`	`flushBefore(long pos)`	Discards the initial portion of the stream prior to the indicated position.
`int`	`getBitOffset()`	Returns the current bit offset, as an integer between 0 and 7, inclusive.
`ByteOrder`	`getByteOrder()`	Returns the byte order with which data values will be read from this stream as an instance of the `java.nio.ByteOrder` enumeration.
`long`	`getFlushedPosition()`	Returns the earliest position in the stream to which seeking may be performed.
`long`	`getStreamPosition()`	Returns the current byte position of the stream.
`long`	`length()`	Returns `-1L` to indicate that the stream has unknown length.
`void`	`mark()`	Pushes the current stream position onto a stack of marked positions.
`int`	`read(byte[] b)`	A convenience method that calls `read(b, 0, b.length)`.
`int`	`readBit()`	Reads a single bit from the stream and returns it as an `int` with the value `0` or `1`.
`long`	`readBits(int numBits)`	Reads a bitstring from the stream and returns it as a `long`, with the first bit read becoming the most significant bit of the output.
`boolean`	`readBoolean()`	Reads a byte from the stream and returns a `boolean` value of `true` if it is nonzero, `false` if it is zero.
`byte`	`readByte()`	Reads a byte from the stream and returns it as a `byte` value.
`void`	`readBytes(IIOByteBuffer buf, int len)`	Reads up to `len` bytes from the stream, and modifies the supplied `IIOByteBuffer` to indicate the byte array, offset, and length where the data may be found.
`char`	`readChar()`	Equivalent to `readUnsignedShort`, except that the result is returned using the `char` datatype.
`double`	`readDouble()`	Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `double`.
`float`	`readFloat()`	Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `float`.
`void`	`readFully(byte[] b)`	Reads `b.length` bytes from the stream, and stores them into `b` starting at index `0`.
`void`	`readFully(byte[] b, int off, int len)`	Reads `len` bytes from the stream, and stores them into `b` starting at index `off`.
`void`	`readFully(char[] c, int off, int len)`	Reads `len` chars (unsigned 16-bit integers) from the stream according to the current byte order, and stores them into `c` starting at index `off`.
`void`	`readFully(double[] d, int off, int len)`	Reads `len` doubles (64-bit IEEE double-precision floats) from the stream according to the current byte order, and stores them into `d` starting at index `off`.
`void`	`readFully(float[] f, int off, int len)`	Reads `len` floats (32-bit IEEE single-precision floats) from the stream according to the current byte order, and stores them into `f` starting at index `off`.
`void`	`readFully(int[] i, int off, int len)`	Reads `len` ints (signed 32-bit integers) from the stream according to the current byte order, and stores them into `i` starting at index `off`.
`void`	`readFully(long[] l, int off, int len)`	Reads `len` longs (signed 64-bit integers) from the stream according to the current byte order, and stores them into `l` starting at index `off`.
`void`	`readFully(short[] s, int off, int len)`	Reads `len` shorts (signed 16-bit integers) from the stream according to the current byte order, and stores them into `s` starting at index `off`.
`int`	`readInt()`	Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as an `int`.
`String`	`readLine()`	Reads the next line of text from the input stream.
`long`	`readLong()`	Reads 8 bytes from the stream, and (conceptually) concatenates them according to the current byte order and returns the result as a `long`.
`short`	`readShort()`	Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, and returns the result as a `short` value.
`int`	`readUnsignedByte()`	Reads a byte from the stream, and (conceptually) converts it to an int, masks it with `0xff` in order to strip off any sign-extension bits, and returns it as a `byte` value.
`long`	`readUnsignedInt()`	Reads 4 bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the result to a long, masks it with `0xffffffffL` in order to strip off any sign-extension bits, and returns the result as an unsigned `long` value.
`int`	`readUnsignedShort()`	Reads two bytes from the stream, and (conceptually) concatenates them according to the current byte order, converts the resulting value to an `int`, masks it with `0xffff` in order to strip off any sign-extension buts, and returns the result as an unsigned `int` value.
`String`	`readUTF()`	Reads in a string that has been encoded using a modified UTF-8 format.
`void`	`reset()`	Resets the current stream byte and bit positions from the stack of marked positions.
`void`	`seek(long pos)`	Sets the current stream position to the desired location.
`void`	`setBitOffset(int bitOffset)`	Sets the bit offset to an integer between 0 and 7, inclusive.
`void`	`setByteOrder(ByteOrder byteOrder)`	Sets the desired byte order for future reads of data values from this stream.
`int`	`skipBytes(int n)`	Advances the current stream position by calling `seek(getStreamPosition() + n)`.
`long`	`skipBytes(long n)`	Advances the current stream position by calling `seek(getStreamPosition() + n)`.

Methods declared in class Object

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

Modifier and Type	Method	Description
`protected Object`	`clone()`	Creates and returns a copy of this object.
`boolean`	`equals(Object obj)`	Indicates whether some other object is "equal to" this one.
`protected void`	`finalize()`	Deprecated, for removal: This API element is subject to removal in a future version. Finalization is deprecated and subject to removal in a future release.
`final Class<?>`	`getClass()`	Returns the runtime class of this `Object`.
`int`	`hashCode()`	Returns a hash code value for this object.
`final void`	`notify()`	Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()`	Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()`	Returns a string representation of the object.
`final void`	`wait()`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted.
`final void`	`wait(long timeoutMillis)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis, int nanos)`	Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.

Constructor Details

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 Details

read

public int read() throws IOException

Description copied from class: ImageInputStreamImpl

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
Specified by:: read in class ImageInputStreamImpl
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, 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.

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:

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:

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:

close

public void close() throws IOException

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

Throws:: IOException - if an I/O error occurs.

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