readHeadersFrame() — netty Function Reference

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java lines 411–483

    private void readHeadersFrame(final ChannelHandlerContext ctx, ByteBuf payload,
            Http2FrameListener listener) throws Http2Exception {
        final int headersStreamId = streamId;
        final Http2Flags headersFlags = flags;
        final int padding = readPadding(payload);

        // The callback that is invoked is different depending on whether priority information
        // is present in the headers frame.
        if (flags.priorityPresent()) {
            long word1 = payload.readUnsignedInt();
            final boolean exclusive = (word1 & 0x80000000L) != 0;
            final int streamDependency = (int) (word1 & 0x7FFFFFFFL);
            if (streamDependency == streamId) {
                // Stream dependencies are deprecated in RFC 9113 but this behavior is defined in
                // https://datatracker.ietf.org/doc/html/rfc7540#section-5.3.1 which says this must be treated as a
                // stream error of type PROTOCOL_ERROR. However, because we will not process the payload, a stream
                // error would result in HPACK corruption. Therefor, it is elevated to a connection error.
                throw connectionError(
                        PROTOCOL_ERROR, "HEADERS frame for stream %d cannot depend on itself.", streamId);
            }
            final short weight = (short) (payload.readUnsignedByte() + 1);
            final int lenToRead = lengthWithoutTrailingPadding(payload.readableBytes(), padding);

            // Create a handler that invokes the listener when the header block is complete.
            headersContinuation = new HeadersContinuation() {
                @Override
                public int getStreamId() {
                    return headersStreamId;
                }

                @Override
                public void processFragment(boolean endOfHeaders, ByteBuf fragment, int len,
                        Http2FrameListener listener) throws Http2Exception {
                    final HeadersBlockBuilder hdrBlockBuilder = headersBlockBuilder();
                    hdrBlockBuilder.addFragment(fragment, len, ctx.alloc(), endOfHeaders);
                    if (endOfHeaders) {
                        listener.onHeadersRead(ctx, headersStreamId, hdrBlockBuilder.headers(), streamDependency,
                                weight, exclusive, padding, headersFlags.endOfStream());
                    }
                }
            };

            // Process the initial fragment, invoking the listener's callback if end of headers.
            headersContinuation.processFragment(flags.endOfHeaders(), payload, lenToRead, listener);
            resetHeadersContinuationIfEnd(flags.endOfHeaders());
            return;
        }

        // The priority fields are not present in the frame. Prepare a continuation that invokes
        // the listener callback without priority information.
        headersContinuation = new HeadersContinuation() {
            @Override
            public int getStreamId() {
                return headersStreamId;
            }

            @Override
            public void processFragment(boolean endOfHeaders, ByteBuf fragment, int len,
                    Http2FrameListener listener) throws Http2Exception {
                final HeadersBlockBuilder hdrBlockBuilder = headersBlockBuilder();
                hdrBlockBuilder.addFragment(fragment, len, ctx.alloc(), endOfHeaders);
                if (endOfHeaders) {
                    listener.onHeadersRead(ctx, headersStreamId, hdrBlockBuilder.headers(), padding,
                                    headersFlags.endOfStream());
                }
            }
        };

        // Process the initial fragment, invoking the listener's callback if end of headers.
        int len = lengthWithoutTrailingPadding(payload.readableBytes(), padding);
        headersContinuation.processFragment(flags.endOfHeaders(), payload, len, listener);
        resetHeadersContinuationIfEnd(flags.endOfHeaders());
    }