uk.ac.starlink.table.storage.NioByteStoreAccess Maven / Gradle / Ivy
Show all versions of stil Show documentation
package uk.ac.starlink.table.storage;
import java.io.IOException;
import java.nio.ByteBuffer;
/**
* Partial implementation of ByteStoreAccess.
* Not thread-safe.
*
* @author Mark Taylor
* @since 20 Aug 2010
*/
public abstract class NioByteStoreAccess implements ByteStoreAccess {
/**
* Returns a buffer with at least the requested number of bytes
* between the current position and the limit.
* When nbyte bytes have been read from the returned
* buffer, the current position of this ByteStoreAccess will have
* advanced by nbyte bytes. The position in the case
* that this call is made with no corresponding read is undefined,
* so it's important that the read is actually done (don't call
* this method speculatively).
*
* If no such buffer is available (the end of the storage has
* been reached), then an IOException will be thrown.
*
* @param nbyte number of bytes required
* @return buffer from which nbyte bytes can be read
*/
protected abstract ByteBuffer getBuffer( int nbyte ) throws IOException;
public byte readByte() throws IOException {
return getBuffer( 1 ).get();
}
public short readShort() throws IOException {
return getBuffer( 2 ).getShort();
}
public char readChar() throws IOException {
return getBuffer( 2 ).getChar();
}
public int readInt() throws IOException {
return getBuffer( 4 ).getInt();
}
public long readLong() throws IOException {
return getBuffer( 8 ).getLong();
}
public float readFloat() throws IOException {
return getBuffer( 4 ).getFloat();
}
public double readDouble() throws IOException {
return getBuffer( 8 ).getDouble();
}
public void readBytes( byte[] b, int offset, int length )
throws IOException {
getBuffer( length ).get( b, offset, length );
}
/**
* Utility method to make a deep copy of an array of ByteBuffers.
*
* @param bufs input buffers
* @return matching array with buffers that are duplicates of the input
* elements
*/
public static ByteBuffer[] copyBuffers( ByteBuffer[] bufs ) {
int nbuf = bufs.length;
ByteBuffer[] bufs1 = new ByteBuffer[ nbuf ];
for ( int i = 0; i < nbuf; i++ ) {
bufs1[ i ] = bufs[ i ].duplicate();
}
return bufs1;
}
/**
* Returns a reader implementation for an array of ByteBuffers.
*
* @param bbufs buffer array
* @return reader implementation
*/
public static ByteStoreAccess createAccess( ByteBuffer[] bbufs ) {
if ( bbufs.length == 1 ) {
return new SingleNioAccess( bbufs[ 0 ] );
}
else {
return new MultiNioAccess( bbufs );
}
}
}