reactive html encoder

HtmlEntityEncoder.java

/**
 * Reactive HTML entities "encoder".
 */
class HtmlEntityEncoder extends BaseProcessor<DataChunk, DataChunk> {

    private static final ByteBufferCache BBCACHE = new ByteBufferCache(
            (int index) -> ByteBuffer.wrap(HtmlEscape.ENTITIES[index][1].getBytes()), HtmlEscape.ENTITIES.length);

    protected final VirtualBuffer vbuf = new VirtualBuffer();
    private boolean started;

    /**
     * Create a new encoder.
     */
    HtmlEntityEncoder() {
    }

    protected final void insert(ByteBuffer bb) {
        vbuf.insert(bb);
        vbuf.incrementPosition(bb.remaining());
    }

    /**
     * Signals the start of the page.
     */
    protected void onPageStart(){ }

    /**
     * Signals the end of the page.
     */
    protected void onPageEnd() { }

    @Override
    public final void hookOnNext(DataChunk item) {
        vbuf.offer(item.data());
        VirtualChunk.Parent parent = new VirtualChunk.Parent(item);
        if (!started) {
            onPageStart();
            started = true;
        }
        while (vbuf.remaining() > 0) {
            byte b1 = vbuf.get();
            int mark = vbuf.position();
            int limit = vbuf.limit();
            int nbytes = 0;
            char c = '?';
            if (b1 >= 0) {
                nbytes = 1;
                c = (char) b1;
            } else if ((b1 >> 5) == -2 && (b1 & 0x1e) != 0) {
                // 2 bytes, 11 bits: 110xxxxx 10xxxxxx
                int b2 = vbuf.get();
                if (!((b2 & 0xc0) != 0x80)) {
                    nbytes = 2;
                    c = (char) (((b1 << 6) ^ b2)
                            ^ (((byte) 0xC0 << 6)
                            ^ ((byte) 0x80)));
                }
            } else if ((b1 >> 4) == -2) {
                // 3 bytes, 16 bits: 1110xxxx 10xxxxxx 10xxxxxx
                int remaining = limit - mark;
                if (remaining >= 2) {
                    int b2 = vbuf.get();
                    int b3 = vbuf.get();
                    if (!((b1 == (byte) 0xe0 && (b2 & 0xe0) == 0x80)
                            || (b2 & 0xc0) != 0x80 || (b3 & 0xc0) != 0x80)) {
                        c = (char) ((b1 << 12)
                                ^ (b2 << 6)
                                ^ (b3
                                ^ (((byte) 0xE0 << 12)
                                ^ ((byte) 0x80 << 6)
                                ^ ((byte) 0x80))));
                        if (!Character.isSurrogate(c)) {
                            nbytes = 3;
                        }
                    }
                }
            }
            int htmlEntityId = HtmlEscape.entityId(c);
            if (htmlEntityId >= 0) {
                vbuf.deletePrevious(nbytes);
                insert(BBCACHE.get(htmlEntityId));
            }
        }

        // It's not possible to submit a VirtualBuffer as-is (yet)
        // using drop() to get the underlying buffers as-is
        for (ByteBuffer bb : vbuf.position(0).drop()) {
            submit(new VirtualChunk(parent, bb));
            // re-using buffers
            bb.position(0);
        }
    }

    @Override
    protected void hookOnComplete() {
        onPageEnd();
        for (ByteBuffer bb : vbuf.position(0).drop()) {
            submit(DataChunk.create(bb));
        }
    }
}