private Http2Settings decodeSettingsHeader(ChannelHandlerContext ctx, CharSequence settingsHeader)
            throws Http2Exception {
        final ByteBuf header = ByteBufUtil.encodeString(ctx.alloc(),
                                                        CharBuffer.wrap(settingsHeader), CharsetUtil.UTF_8);
        try {
            // Decode the SETTINGS payload.
            final ByteBuf payload = Base64.decode(header, URL_SAFE);

            // Create an HTTP/2 frame for the settings.
            final ByteBuf frame = createSettingsFrame(ctx, payload);

            // Decode the SETTINGS frame and return the settings object.
            return decodeSettings(ctx, frame);
        } finally {
            header.release();
        }
    }
Decodes the settings header and returns a {@link Http2Settings} object.
core/src/main/java/com/linecorp/armeria/server/Http2ServerUpgradeCodec.java