HeadersBlockBuilder Class — netty Architecture

Source Code

codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java lines 674–750

    protected class HeadersBlockBuilder {
        private ByteBuf headerBlock;

        /**
         * The local header size maximum has been exceeded while accumulating bytes.
         * @throws Http2Exception A connection error indicating too much data has been received.
         */
        private void headerSizeExceeded() throws Http2Exception {
            close();
            headerListSizeExceeded(headersDecoder.configuration().maxHeaderListSizeGoAway());
        }

        /**
         * Adds a fragment to the block.
         *
         * @param fragment the fragment of the headers block to be added.
         * @param alloc allocator for new blocks if needed.
         * @param endOfHeaders flag indicating whether the current frame is the end of the headers.
         *            This is used for an optimization for when the first fragment is the full
         *            block. In that case, the buffer is used directly without copying.
         */
        final void addFragment(ByteBuf fragment, int len, ByteBufAllocator alloc,
                boolean endOfHeaders) throws Http2Exception {
            if (headerBlock == null) {
                if (len > headersDecoder.configuration().maxHeaderListSizeGoAway()) {
                    headerSizeExceeded();
                }
                if (endOfHeaders) {
                    // Optimization - don't bother copying, just use the buffer as-is. Need
                    // to retain since we release when the header block is built.
                    headerBlock = fragment.readRetainedSlice(len);
                } else {
                    headerBlock = alloc.buffer(len).writeBytes(fragment, len);
                }
                return;
            }
            if (headersDecoder.configuration().maxHeaderListSizeGoAway() - len <
                    headerBlock.readableBytes()) {
                headerSizeExceeded();
            }
            if (headerBlock.isWritable(len)) {
                // The buffer can hold the requested bytes, just write it directly.
                headerBlock.writeBytes(fragment, len);
            } else {
                // Allocate a new buffer that is big enough to hold the entire header block so far.
                ByteBuf buf = alloc.buffer(headerBlock.readableBytes() + len);
                buf.writeBytes(headerBlock).writeBytes(fragment, len);
                headerBlock.release();
                headerBlock = buf;
            }
        }

        /**
         * Builds the headers from the completed headers block. After this is called, this builder
         * should not be called again.
         */
        Http2Headers headers() throws Http2Exception {
            try {
                return headersDecoder.decodeHeaders(streamId, headerBlock);
            } finally {
                close();
            }
        }

        /**
         * Closes this builder and frees any resources.
         */
        void close() {
            if (headerBlock != null) {
                headerBlock.release();
                headerBlock = null;
            }

            // Clear the member variable pointing at this instance.
            headersContinuation = null;
        }
    }