- java.lang.Object
-
- javax.imageio.stream.ImageInputStreamImpl
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- javax.imageio.stream.MemoryCacheImageInputStream
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- All Implemented Interfaces:
- Closeable, DataInput, AutoCloseable, ImageInputStream
public class MemoryCacheImageInputStream extends ImageInputStreamImpl
An implementation ofImageInputStream
that gets its input from a regularInputStream
. 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 regularInputStream
. This class is provided for cases where it is not possible to create a writable temporary file.
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Field Summary
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Fields inherited from class javax.imageio.stream.ImageInputStreamImpl
bitOffset, byteOrder, flushedPos, streamPos
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Constructor Summary
Constructors Constructor and Description MemoryCacheImageInputStream(InputStream stream)
Constructs aMemoryCacheImageInputStream
that will read from a givenInputStream
.
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Method Summary
Methods Modifier and Type Method and Description void
close()
Closes thisMemoryCacheImageInputStream
, freeing the cache.protected void
finalize()
Finalizes this object prior to garbage collection.void
flushBefore(long pos)
Discards the initial portion of the stream prior to the indicated postion.boolean
isCached()
Returnstrue
since thisImageInputStream
caches data in order to allow seeking backwards.boolean
isCachedFile()
Returnsfalse
since thisImageInputStream
does not maintain a file cache.boolean
isCachedMemory()
Returnstrue
since thisImageInputStream
maintains a main memory cache.int
read()
Reads a single byte from the stream and returns it as anint
between 0 and 255.int
read(byte[] b, int off, int len)
Reads up tolen
bytes from the stream, and stores them intob
starting at indexoff
.-
Methods inherited from class javax.imageio.stream.ImageInputStreamImpl
checkClosed, 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
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Constructor Detail
-
MemoryCacheImageInputStream
public MemoryCacheImageInputStream(InputStream stream)
Constructs aMemoryCacheImageInputStream
that will read from a givenInputStream
.- Parameters:
stream
- anInputStream
to read from.- Throws:
IllegalArgumentException
- ifstream
isnull
.
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Method Detail
-
read
public int read() throws IOException
Description copied from class:ImageInputStreamImpl
Reads a single byte from the stream and returns it as anint
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 interfaceImageInputStream
- Specified by:
read
in classImageInputStreamImpl
- 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 tolen
bytes from the stream, and stores them intob
starting at indexoff
. 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 interfaceImageInputStream
- Specified by:
read
in classImageInputStreamImpl
- Parameters:
b
- an array of bytes to be written to.off
- the starting position withinb
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.
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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 anIndexOutOfBoundsException
.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 interfaceImageInputStream
- Overrides:
flushBefore
in classImageInputStreamImpl
- Parameters:
pos
- along
containing the length of the stream prefix that may be flushed.- Throws:
IOException
- if an I/O error occurs.
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isCached
public boolean isCached()
Returnstrue
since thisImageInputStream
caches data in order to allow seeking backwards.- Specified by:
isCached
in interfaceImageInputStream
- Overrides:
isCached
in classImageInputStreamImpl
- Returns:
true
.- See Also:
isCachedMemory()
,isCachedFile()
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isCachedFile
public boolean isCachedFile()
Returnsfalse
since thisImageInputStream
does not maintain a file cache.- Specified by:
isCachedFile
in interfaceImageInputStream
- Overrides:
isCachedFile
in classImageInputStreamImpl
- Returns:
false
.- See Also:
isCached()
,isCachedMemory()
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isCachedMemory
public boolean isCachedMemory()
Returnstrue
since thisImageInputStream
maintains a main memory cache.- Specified by:
isCachedMemory
in interfaceImageInputStream
- Overrides:
isCachedMemory
in classImageInputStreamImpl
- Returns:
true
.- See Also:
isCached()
,isCachedFile()
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close
public void close() throws IOException
Closes thisMemoryCacheImageInputStream
, freeing the cache. The sourceInputStream
is not closed.- Specified by:
close
in interfaceCloseable
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceImageInputStream
- Overrides:
close
in classImageInputStreamImpl
- Throws:
IOException
- if an I/O error occurs.
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finalize
protected void finalize() throws Throwable
Finalizes this object prior to garbage collection. Theclose
method is called to close any open input source. This method should not be called from application code.- Overrides:
finalize
in classImageInputStreamImpl
- Throws:
Throwable
- if an error occurs during superclass finalization.
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Document created the 11/06/2005, last modified the 04/03/2020
Source of the printed document:https://www.gaudry.be/en/java-api-rf-javax/imageio/stream/MemoryCacheImageInputStream.html
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