| java.lang.Object
 javax.imageio.stream.MemoryCache
| MemoryCache | | class MemoryCache (Code) | | Package-visible class consolidating common code for
MemoryCacheImageInputStream and
MemoryCacheImageOutputStream.
This class keeps an ArrayList of 8K blocks,
loaded sequentially. Blocks may only be disposed of
from the index 0 forward. As blocks are freed, the
corresponding entries in the array list are set to
null, but no compacting is performed.
This allows the index for each block to never change,
and the length of the cache is always the same as the
total amount of data ever cached. Cached data is
therefore always contiguous from the point of last
disposal to the current length.
The total number of blocks resident in the cache must not
exceed Integer.MAX_VALUE. In practice, the limit of
available memory will be exceeded long before this becomes an
issue, since a full cache would contain 8192*2^31 = 16 terabytes of
data.
A MemoryCache may be reused after a call
to reset().
|
| Method Summary | |
| public void | disposeBefore(long pos)
Free the blocks up to the position pos. | | public long | getLength()
Returns the total length of data that has been cached,
regardless of whether any early blocks have been disposed. | | public long | loadFromStream(InputStream stream, long pos)
Ensures that at least pos bytes are cached,
or the end of the source is reached. | | public int | read(long pos)
Returns the single byte at the given position, as an
int. | | public void | read(byte[] b, int off, int len, long pos)
Copy len bytes from the cache, starting
at cache position pos, into the array
b at offset off. | | public void | reset()
Erase the entire cache contents and reset the length to 0. | | public void | write(byte[] b, int off, int len, long pos)
Overwrites and/or appends the cache from a byte array. | | public void | write(int b, long pos)
Overwrites or appends a single byte to the cache. | | public void | writeToStream(OutputStream stream, long pos, long len)
Writes out a portion of the cache to an OutputStream.
This method preserves no state about the output stream, and does
not dispose of any blocks containing bytes written. |
| disposeBefore | | public void disposeBefore(long pos)(Code) | | Free the blocks up to the position pos.
The byte at pos remains available.
exception:
IndexOutOfBoundsException - if posis in a block that has already been disposed. |
| getLength | | public long getLength()(Code) | | Returns the total length of data that has been cached,
regardless of whether any early blocks have been disposed.
This value will only ever increase.
|
| loadFromStream | | public long loadFromStream(InputStream stream, long pos) throws IOException(Code) | | Ensures that at least pos bytes are cached,
or the end of the source is reached. The return value
is equal to the smaller of pos and the
length of the source.
|
| read | | public int read(long pos) throws IOException(Code) | | Returns the single byte at the given position, as an
int. Returns -1 if this position has
not been cached or has been disposed.
|
| read | | public void read(byte[] b, int off, int len, long pos) throws IOException(Code) | | Copy len bytes from the cache, starting
at cache position pos, into the array
b at offset off.
exception:
NullPointerException - if b is null
exception:
IndexOutOfBoundsException - if off,len or pos are negative or ifoff + len > b.length or if any portion of therequested data is not in the cache (including ifpos is in a block that has already been disposed). |
| reset | | public void reset()(Code) | | Erase the entire cache contents and reset the length to 0.
The cache object may subsequently be reused as though it had just
been allocated.
|
| write | | public void write(byte[] b, int off, int len, long pos) throws IOException(Code) | | Overwrites and/or appends the cache from a byte array.
The length of the cache will be extended as needed to hold
the incoming data.
Parameters:
b - an array of bytes containing data to be written.
Parameters:
off - the starting offset withing the data array.
Parameters:
len - the number of bytes to be written.
Parameters:
pos - the cache position at which to begin writing.
exception:
NullPointerException - if b is null.
exception:
IndexOutOfBoundsException - if off,len, or pos are negative,or if off+len > b.length. |
| write | | public void write(int b, long pos) throws IOException(Code) | | Overwrites or appends a single byte to the cache.
The length of the cache will be extended as needed to hold
the incoming data.
Parameters:
b - an int whose 8 least significant bitswill be written.
Parameters:
pos - the cache position at which to begin writing.
exception:
IndexOutOfBoundsException - if pos is negative. |
| writeToStream | | public void writeToStream(OutputStream stream, long pos, long len) throws IOException(Code) | | Writes out a portion of the cache to an OutputStream.
This method preserves no state about the output stream, and does
not dispose of any blocks containing bytes written. To dispose
blocks, use
MemoryCache.disposeBefore disposeBefore() .
exception:
IndexOutOfBoundsException - if any portion ofthe requested data is not in the cache (including if posis in a block already disposed), or if either pos or len is < 0. |
|
|