msgpack-v07-unpacker-design-doc.java

public interface XyzInput {
    public Buffer getNextBuffer() throws IOException;
}
 
// non-reference counter
public abstract class Buffer {
    private Unsafe unsafe;
 
    private long pointer;
    private Object base;
    private int size;
 
    protected Buffer(ByteBuffer bb) {
        this.pointer = // from bb ...
        this.base = // from bb ...
    }
 
    public int getInt(int offset) {
        return unsafe.getInt(base, pointer);
    }
 
    // getLong(int offset)
    // getShort(int offset)
    // ...
 
    public abstract void release();
 
    public int size() {
        return size;
    }
}
 
// reference counter
public abstract class Buffer {
    private Unsafe unsafe;
 
    private long pointer;
    private Object base;
    private int offset;
    private int size;
 
    private AtomicInteger referenceCounter;
 
    static {
        // something depending on architecture to get unsafe
        //@Suppress...
    }
 
    protected Buffer(ByteBuffer bb) {
        if(bb.hasArray()) {
            // Nonn-direct buffer
            this.pointer = // from bb ...
            this.offset = bb.arrayOffset();
            this.base = bb.array();
        } else {
            // DirectBuffer
            // See airlift Slice code
            this.pointer = bb.xyz;
            this.offset = 0;
            this.base = null;
        }
    }
 
    public int getInt(int offset) {
        return unsafe.getInt(base, offset + pointer);
    }
 
    // getLong(int offset)
    // getShort(int offset)
    // ...
 
    public int size() {
        return size;
    }
 
    public void acquire() {
        referenceCounter.increment(1);
    }
 
    public void release() {
        if(referenceCounter.decrement(1) == 0) {
            releaseBuffer();
        }
    }
 
    protected abstract void releaseBuffer();
}
 
// might be public, but doesn't have to be public
class UnpackerBuffer {
    private byte[] extra;
    private int extraOffset;
 
    private Buffer currentBuffer;
    private int position;
 
    private XyzInput input;
 
    public int readInt() {
        if(currentBuffer.size() < position + 4) {
            currentBuffer.copyTo(extra, position, currentBuffer.size() - position);
            currentBuffer.release();
            currentBuffer = input.getNextBuffer();
            // copy data to extra...
            // TODO
        }
        int v = currentBuffer.getInt(position);
        position += 4;
        return v;
    }
}
 
 
// Implement Unpacker
 
// Performance bnechmark