flatbuffers/cmake: move build_flatbuffers to a standalone file

So that it could be included from both flatbuffers CMakeLists.txt and
FindFlatBuffers.cmake.

Change-Id: Ie16a879beef9367cd6fd9b2d2157044841a7cdbc

2 files changed, 145 insertions, 0 deletions

diff --git a/CMake/BuildFlatBuffers.cmake b/CMake/BuildFlatBuffers.cmake
new file mode 100644
index 00000000..2c28899a
--- /dev/null
+++ b/CMake/BuildFlatBuffers.cmake
@@ -0,0 +1,141 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# General function to create FlatBuffer build rules for the given list of
+# schemas.
+#
+# flatbuffers_schemas: A list of flatbuffer schema files to process.
+#
+# schema_include_dirs: A list of schema file include directories, which will be
+# passed to flatc via the -I parameter.
+#
+# custom_target_name: The generated files will be added as dependencies for a
+# new custom target with this name. You should add that target as a dependency
+# for your main target to ensure these files are built. You can also retrieve
+# various properties from this target, such as GENERATED_INCLUDES_DIR,
+# BINARY_SCHEMAS_DIR, and COPY_TEXT_SCHEMAS_DIR.
+#
+# additional_dependencies: A list of additional dependencies that you'd like
+# all generated files to depend on. Pass in a blank string if you have none.
+#
+# generated_includes_dir: Where to generate the C++ header files for these
+# schemas. The generated includes directory will automatically be added to
+# CMake's include directories, and will be where generated header files are
+# placed. This parameter is optional; pass in empty string if you don't want to
+# generate include files for these schemas.
+#
+# binary_schemas_dir: If you specify an optional binary schema directory, binary
+# schemas will be generated for these schemas as well, and placed into the given
+# directory.
+#
+# copy_text_schemas_dir: If you want all text schemas (including schemas from
+# all schema include directories) copied into a directory (for example, if you
+# need them within your project to build JSON files), you can specify that
+# folder here. All text schemas will be copied to that folder.
+#
+# IMPORTANT: Make sure you quote all list arguments you pass to this function!
+# Otherwise CMake will only pass in the first element.
+# Example: build_flatbuffers("${fb_files}" "${include_dirs}" target_name ...)
+function(build_flatbuffers flatbuffers_schemas
+                           schema_include_dirs
+                           custom_target_name
+                           additional_dependencies
+                           generated_includes_dir
+                           binary_schemas_dir
+                           copy_text_schemas_dir)
+
+  # Test if including from FindFlatBuffers
+  if(FLATBUFFERS_FLATC_EXECUTABLE)
+    set(FLATC_TARGET "")
+    set(FLATC ${FLATBUFFERS_FLATC_EXECUTABLE})
+  else()
+    set(FLATC_TARGET flatc)
+    set(FLATC flatc)
+  endif()
+
+  set(schema_glob "*.fbs")
+  # Generate the include files parameters.
+  set(include_params "")
+  set(all_generated_files "")
+  foreach (include_dir ${schema_include_dirs})
+    set(include_params -I ${include_dir} ${include_params})
+    if (NOT ${copy_text_schemas_dir} STREQUAL "")
+      # Copy text schemas from dependent folders.
+      file(GLOB_RECURSE dependent_schemas ${include_dir}/${schema_glob})
+      foreach (dependent_schema ${dependent_schemas})
+        file(COPY ${dependent_schema} DESTINATION ${copy_text_schemas_dir})
+      endforeach()
+    endif()
+  endforeach()
+
+  foreach(schema ${flatbuffers_schemas})
+    get_filename_component(filename ${schema} NAME_WE)
+    # For each schema, do the things we requested.
+    if (NOT ${generated_includes_dir} STREQUAL "")
+      set(generated_include ${generated_includes_dir}/${filename}_generated.h)
+      add_custom_command(
+        OUTPUT ${generated_include}
+        COMMAND ${FLATC} --gen-mutable
+        -o ${generated_includes_dir}
+        ${include_params}
+        -c ${schema}
+        DEPENDS ${FLATC_TARGET} ${schema} ${additional_dependencies})
+      list(APPEND all_generated_files ${generated_include})
+    endif()
+
+    if (NOT ${binary_schemas_dir} STREQUAL "")
+      set(binary_schema ${binary_schemas_dir}/${filename}.bfbs)
+      add_custom_command(
+        OUTPUT ${binary_schema}
+        COMMAND ${FLATC} -b --schema
+        -o ${binary_schemas_dir}
+        ${include_params}
+        ${schema}
+        DEPENDS ${FLATC_TARGET} ${schema} ${additional_dependencies})
+      list(APPEND all_generated_files ${binary_schema})
+    endif()
+
+    if (NOT ${copy_text_schemas_dir} STREQUAL "")
+      file(COPY ${schema} DESTINATION ${copy_text_schemas_dir})
+    endif()
+  endforeach()
+
+  # Create a custom target that depends on all the generated files.
+  # This is the target that you can depend on to trigger all these
+  # to be built.
+  add_custom_target(${custom_target_name}
+                    DEPENDS ${all_generated_files} ${additional_dependencies})
+
+  # Register the include directory we are using.
+  if (NOT ${generated_includes_dir} STREQUAL "")
+    include_directories(${generated_includes_dir})
+    set_property(TARGET ${custom_target_name}
+      PROPERTY GENERATED_INCLUDES_DIR
+      ${generated_includes_dir})
+  endif()
+
+  # Register the binary schemas dir we are using.
+  if (NOT ${binary_schemas_dir} STREQUAL "")
+    set_property(TARGET ${custom_target_name}
+      PROPERTY BINARY_SCHEMAS_DIR
+      ${binary_schemas_dir})
+  endif()
+
+  # Register the text schema copy dir we are using.
+  if (NOT ${copy_text_schemas_dir} STREQUAL "")
+    set_property(TARGET ${custom_target_name}
+      PROPERTY COPY_TEXT_SCHEMAS_DIR
+      ${copy_text_schemas_dir})
+  endif()
+endfunction()
diff --git a/CMake/FindFlatBuffers.cmake b/CMake/FindFlatBuffers.cmake
index 0a54e2a2..675ea887 100644
--- a/CMake/FindFlatBuffers.cmake
+++ b/CMake/FindFlatBuffers.cmake
@@ -24,6 +24,8 @@
 #   for the given flatbuffer schema files.
 #   Returns the header files in ${Name}_OUTPUTS
 
+set(FLATBUFFERS_CMAKE_DIR ${CMAKE_CURRENT_LIST_DIR})
+
 find_program(FLATBUFFERS_FLATC_EXECUTABLE NAMES flatc)
 find_path(FLATBUFFERS_INCLUDE_DIR NAMES flatbuffers/flatbuffers.h)
 
@@ -54,3 +56,5 @@ if(FLATBUFFERS_FOUND)
 else()
   set(FLATBUFFERS_INCLUDE_DIR)
 endif()
+
+include("${FLATBUFFERS_CMAKE_DIR}/BuildFlatBuffers.cmake")
\ No newline at end of file