Add leveldb to the Firestore cmake build (#559)

* Use Debug as the default build type if unspecified

* Add a leveldb ExternalProject, FindLevelDB module, and use it in Firestore

* Accept an externally built leveldb via LEVELDB_ROOT

* Clone leveldb via https: instead of git:

* Remove extra DOWNLOAD_DIR which doesn't work with GIT sources

1 files changed, 55 insertions, 0 deletions

diff --git a/cmake/FindLevelDB.cmake b/cmake/FindLevelDB.cmake
new file mode 100644
index 0000000..ae32a17
--- /dev/null
+++ b/cmake/FindLevelDB.cmake
@@ -0,0 +1,55 @@
+# Copyright 2017 Google
+#
+# 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.
+
+set(binary_dir ${FIREBASE_BINARY_DIR}/third_party/leveldb/src/leveldb)
+
+find_path(
+  LEVELDB_INCLUDE_DIR leveldb/db.h
+  HINTS
+    $ENV{LEVELDB_ROOT}/include
+    ${LEVELDB_ROOT}/include
+    ${binary_dir}/include
+  PATH_SUFFIXES leveldb
+)
+
+find_library(
+  LEVELDB_LIBRARY
+  NAMES leveldb
+  HINTS
+    $ENV{LEVELDB_ROOT}/lib
+    ${LEVELDB_ROOT}/lib
+    ${binary_dir}/out-static
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(
+  LevelDB
+  DEFAULT_MSG
+  LEVELDB_INCLUDE_DIR
+  LEVELDB_LIBRARY
+)
+
+if(LEVELDB_FOUND)
+  set(LEVELDB_INCLUDE_DIRS ${LEVELDB_INCLUDE_DIR})
+  set(LEVELDB_LIBRARIES ${LEVELDB_LIBRARY})
+
+  if (NOT TARGET LevelDB::LevelDB)
+    add_library(LevelDB::LevelDB UNKNOWN IMPORTED)
+    set_target_properties(
+      LevelDB::LevelDB PROPERTIES
+      INTERFACE_INCLUDE_DIRECTORIES ${LEVELDB_INCLUDE_DIR}
+      IMPORTED_LOCATION ${LEVELDB_LIBRARY}
+    )
+  endif()
+endif(LEVELDB_FOUND)