DefaultHttp2HeadersDecoder Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2HeadersDecoder.java lines 26–211

public class DefaultHttp2HeadersDecoder implements Http2HeadersDecoder, Http2HeadersDecoder.Configuration {
    private static final float HEADERS_COUNT_WEIGHT_NEW = 1 / 5f;
    private static final float HEADERS_COUNT_WEIGHT_HISTORICAL = 1 - HEADERS_COUNT_WEIGHT_NEW;

    private final HpackDecoder hpackDecoder;
    private final boolean validateHeaders;
    private final boolean validateHeaderValues;
    private long maxHeaderListSizeGoAway;

    /**
     * Used to calculate an exponential moving average of header sizes to get an estimate of how large the data
     * structure for storing headers should be.
     */
    private float headerArraySizeAccumulator = 8;

    public DefaultHttp2HeadersDecoder() {
        this(true);
    }

    /**
     * Create a new instance.
     * @param validateHeaders {@code true} to validate headers are valid according to the RFC.
     */
    public DefaultHttp2HeadersDecoder(boolean validateHeaders) {
        this(validateHeaders, DEFAULT_HEADER_LIST_SIZE);
    }

    /**
     * Create a new instance.
     *
     * @param validateHeaders {@code true} to validate headers are valid according to the RFC.
     * This validates everything except header values.
     * @param validateHeaderValues {@code true} to validate that header <em>values</em> are valid according to the RFC.
     * Since this is potentially expensive, it can be enabled separately from {@code validateHeaders}.
     */
    public DefaultHttp2HeadersDecoder(boolean validateHeaders, boolean validateHeaderValues) {
        this(validateHeaders, validateHeaderValues, DEFAULT_HEADER_LIST_SIZE);
    }

    /**
     * Create a new instance.
     * @param validateHeaders {@code true} to validate headers are valid according to the RFC.
     * @param maxHeaderListSize This is the only setting that can be configured before notifying the peer.
     *  This is because <a href="https://tools.ietf.org/html/rfc7540#section-6.5.1">SETTINGS_MAX_HEADER_LIST_SIZE</a>
     *  allows a lower than advertised limit from being enforced, and the default limit is unlimited
     *  (which is dangerous).
     */
    public DefaultHttp2HeadersDecoder(boolean validateHeaders, long maxHeaderListSize) {
        this(validateHeaders, false, new HpackDecoder(maxHeaderListSize));
    }

    /**
     * Create a new instance.
     * @param validateHeaders {@code true} to validate headers are valid according to the RFC.
     * This validates everything except header values.
     * @param validateHeaderValues {@code true} to validate that header <em>values</em> are valid according to the RFC.
     * Since this is potentially expensive, it can be enabled separately from {@code validateHeaders}.
     * @param maxHeaderListSize This is the only setting that can be configured before notifying the peer.
     *  This is because <a href="https://tools.ietf.org/html/rfc7540#section-6.5.1">SETTINGS_MAX_HEADER_LIST_SIZE</a>
     *  allows a lower than advertised limit from being enforced, and the default limit is unlimited
     *  (which is dangerous).
     */
    public DefaultHttp2HeadersDecoder(boolean validateHeaders, boolean validateHeaderValues, long maxHeaderListSize) {
        this(validateHeaders, validateHeaderValues, new HpackDecoder(maxHeaderListSize));
    }

    /**
     * Create a new instance.
     * @param validateHeaders {@code true} to validate headers are valid according to the RFC.
     * This validates everything except header values.
     * @param maxHeaderListSize This is the only setting that can be configured before notifying the peer.
     *  This is because <a href="https://tools.ietf.org/html/rfc7540#section-6.5.1">SETTINGS_MAX_HEADER_LIST_SIZE</a>
     *  allows a lower than advertised limit from being enforced, and the default limit is unlimited
     *  (which is dangerous).
     * @param initialHuffmanDecodeCapacity Does nothing, do not use.
     */
    public DefaultHttp2HeadersDecoder(boolean validateHeaders, long maxHeaderListSize,
                                      @Deprecated int initialHuffmanDecodeCapacity) {
        this(validateHeaders, false, new HpackDecoder(maxHeaderListSize));
    }