com.bigdata.rwstore

Class PSOutputStream

java.lang.Object

java.io.OutputStream

com.bigdata.rawstore.IPSOutputStream

com.bigdata.rwstore.PSOutputStream

All Implemented Interfaces:

Closeable, Flushable, AutoCloseable

public class PSOutputStream
extends IPSOutputStream

PSOutputStream Provides stream interface direct to the low-level store.

Retrieved from an IObjectStore to enable output to the store.

The key idea here is that rather than a call like :

        store.realloc(oldAddr, byteOutputStream)=> newAddress
 
 instead :
        store.allocStream(oldAddr)=>PSOutputStream

 and then :
        stream.save()=> newAddress
 

This will enable large data formats to be streamed to the data store, where the previous interface would have required that the entire resource was loaded into a memory structure first, before being written out in a single block to the store.

This new approach will also enable the removal of BLOB allocation strategy. Instead, "BLOBS" will be served by linked fixed allocation blocks, flushed out by the stream.

A big advantage of this is that BLOB reallocation is now a lot simpler, since BLOB storage is simply a potentially large number of 8K blocks.

This also opens up the possibility of a Stream oriented data type, that could be used to serve up a variety of data streams. By providing relevant interfaces with the client/server system, a server can then provide multiple streams to a high number of clients.

To this end, the output stream has a fixed buffer size, and they are recycled from a pool of output streams.

It is important that output streams are bound to the IStore they are requested for.

See ticket #641 that discusses creating and using a pool for PSOutputStream allocation.

Constructor Summary

Constructors

Constructor and Description
PSOutputStream()

Method Summary

Methods

Modifier and Type	Method and Description
void	close()
long	getAddr() Called when writes to the stream are complete.
int	getBytesWritten()
OutputStream	getFilterWrapper(boolean saveBeforeClose)
static PSOutputStream	getNew(IStore store, int maxAlloc, IAllocationContext context)
void	reset()
long	save() on save() the current buffer is allocated and written to the store, and the address of its location returned If saving as Blob then addr must index to the BlobAllocator that then points to the BlobHeader
void	write(byte[] b, int off, int len) write byte array to the buffer we need to be able to efficiently handle large arrays beyond size of the blobThreshold, so
void	write(InputStream instr) utility method that extracts data from the input stream
void	write(int b) write a single byte this is the one place where the blob threshold is handled and its done one byte at a time so should be easy enough, We no longer store continuation addresses, instead we allocate blob allocations via a blob header block.
void	writeInt(int b) write a single 4 byte integer
void	writeLong(long b)

Methods inherited from class java.io.OutputStream

flush, write

Methods inherited from class java.lang.Object

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

Constructor Detail

PSOutputStream

public PSOutputStream()

Method Detail

getNew

public static PSOutputStream getNew(IStore store,
                    int maxAlloc,
                    IAllocationContext context)

reset

public void reset()

write

public void write(int b)
           throws IOException

write a single byte this is the one place where the blob threshold is handled and its done one byte at a time so should be easy enough, We no longer store continuation addresses, instead we allocate blob allocations via a blob header block.

Specified by:

write in class OutputStream

Throws:

IOException

writeInt

public void writeInt(int b)
              throws IOException

write a single 4 byte integer

Throws:

IOException

writeLong

public void writeLong(long b)
               throws IOException

Throws:

IOException

write

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

write byte array to the buffer we need to be able to efficiently handle large arrays beyond size of the blobThreshold, so

Overrides:

write in class OutputStream

Throws:

IOException

write

public void write(InputStream instr)
           throws IOException

utility method that extracts data from the input stream

Parameters:

instr - and write to the store. This method can be used to stream external files into the store.

Throws:

IOException

save

public long save()

on save() the current buffer is allocated and written to the store, and the address of its location returned If saving as Blob then addr must index to the BlobAllocator that then points to the BlobHeader

close

public void close()
           throws IOException

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class OutputStream

Throws:

IOException

getBytesWritten

public int getBytesWritten()

getFilterWrapper

public OutputStream getFilterWrapper(boolean saveBeforeClose)

getAddr

public long getAddr()

Description copied from class: IPSOutputStream

Called when writes to the stream are complete.

Specified by:

getAddr in class IPSOutputStream

Returns:

the address from which an InputStream can be retrieved.