nullfile.java

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package org.garret.perst;

/**
 * This implementation of <code>IFile</code> interface can be used
 * to make Perst an main-memory database. It should be used when pagePoolSize
 * is set to <code>Storage.INFINITE_PAGE_POOL</code>. In this case all pages are cached in memory
 * and <code>NullFile</code> is used just as a stub.<P>
 * <code>NullFile</code> should be used only when data is transient - i.e. it should not be saved
 * between database sessions. If you need in-memory database but which provide data persistency, 
 * you should use normal file and infinite page pool size. 
 */
public class NullFile implements IFile 
{ 
    public void write(long pos, byte[] buf) {}

    public int read(long pos, byte[] buf) {
        return 0;
    }

    public void sync() {}

    public boolean tryLock(boolean shared) { 
        return true;
    }

    public void lock(boolean shared) { 
    }

    public void unlock() { 
    }

    public void close() {}

    public long length() { 
        return 0;
    }
}