Add Python API (#31)

cmake/pybind11.cmake

@@ -0,0 +1,38 @@
+function(download_pybind11)
+  include(FetchContent)
+
+  set(pybind11_URL  "https://github.com/pybind/pybind11/archive/refs/tags/v2.10.2.tar.gz")
+  set(pybind11_HASH "SHA256=93bd1e625e43e03028a3ea7389bba5d3f9f2596abc074b068e70f4ef9b1314ae")
+
+  # If you don't have access to the Internet,
+  # please pre-download pybind11
+  set(possible_file_locations
+    $ENV{HOME}/Downloads/pybind11-2.10.2.tar.gz
+    ${PROJECT_SOURCE_DIR}/pybind11-2.10.2.tar.gz
+    ${PROJECT_BINARY_DIR}/pybind11-2.10.2.tar.gz
+    /tmp/pybind11-2.10.2.tar.gz
+    /star-fj/fangjun/download/github/pybind11-2.10.2.tar.gz
+  )
+
+  foreach(f IN LISTS possible_file_locations)
+    if(EXISTS ${f})
+      set(pybind11_URL  "file://${f}")
+      break()
+    endif()
+  endforeach()
+
+  FetchContent_Declare(pybind11
+    URL               ${pybind11_URL}
+    URL_HASH          ${pybind11_HASH}
+  )
+
+  FetchContent_GetProperties(pybind11)
+  if(NOT pybind11_POPULATED)
+    message(STATUS "Downloading pybind11 from ${pybind11_URL}")
+    FetchContent_Populate(pybind11)
+  endif()
+  message(STATUS "pybind11 is downloaded to ${pybind11_SOURCE_DIR}")
+  add_subdirectory(${pybind11_SOURCE_DIR} ${pybind11_BINARY_DIR} EXCLUDE_FROM_ALL)
+endfunction()
+
+download_pybind11()