Arrays.fill(buf, (byte) 0);
        synchronized ( this.cache ) {
            if ( this.freeBuffers < this.cache.length ) {
                for ( int i = 0; i < this.cache.length; i++ ) {
                    if ( this.cache[ i ] == null ) {
                        this.cache[ i ] = buf;
                        this.freeBuffers++;
                        return;
                    }