add streaming websocket server and client (#62)

cmake/asio.cmake

@@ -0,0 +1,39 @@
+function(download_asio)
+  include(FetchContent)
+
+  set(asio_URL  "https://github.com/chriskohlhoff/asio/archive/refs/tags/asio-1-24-0.tar.gz")
+  set(asio_HASH "SHA256=cbcaaba0f66722787b1a7c33afe1befb3a012b5af3ad7da7ff0f6b8c9b7a8a5b")
+
+  # If you don't have access to the Internet,
+  # please pre-download asio
+  set(possible_file_locations
+    $ENV{HOME}/Downloads/asio-asio-1-24-0.tar.gz
+    ${PROJECT_SOURCE_DIR}/asio-asio-1-24-0.tar.gz
+    ${PROJECT_BINARY_DIR}/asio-asio-1-24-0.tar.gz
+    /tmp/asio-asio-1-24-0.tar.gz
+    /star-fj/fangjun/download/github/asio-asio-1-24-0.tar.gz
+  )
+
+  foreach(f IN LISTS possible_file_locations)
+    if(EXISTS ${f})
+      set(asio_URL  "file://${f}")
+      break()
+    endif()
+  endforeach()
+
+  FetchContent_Declare(asio
+    URL               ${asio_URL}
+    URL_HASH          ${asio_HASH}
+  )
+
+  FetchContent_GetProperties(asio)
+  if(NOT asio_POPULATED)
+    message(STATUS "Downloading asio ${asio_URL}")
+    FetchContent_Populate(asio)
+  endif()
+  message(STATUS "asio is downloaded to ${asio_SOURCE_DIR}")
+  # add_subdirectory(${asio_SOURCE_DIR} ${asio_BINARY_DIR} EXCLUDE_FROM_ALL)
+  include_directories(${asio_SOURCE_DIR}/asio/include)
+endfunction()
+
+download_asio()