rocksdb cmake

# OSD/ObjectStore
# make rocksdb statically
if(NOT ALLOCATOR STREQUAL "jemalloc")
  set(ROCKSDB_JEMALLOC "DISABLE_JEMALLOC=1")
endif()

set(ROCKSDB_EXTRA_CXXFLAG "-fPIC -Wno-unused-variable")
if(NOT CMAKE_BUILD_TYPE STREQUAL Debug)
  set(ROCKSDB_EXTRA_CXXFLAG "${ROCKSDB_EXTRA_CXXFLAG} -DNDEBUG")
endif(NOT CMAKE_BUILD_TYPE STREQUAL Debug)

set(ROCKSDB_CXX "${CMAKE_CXX_COMPILER}")
if (WITH_CCACHE AND CCACHE_FOUND)
  set(ROCKSDB_CXX "ccache ${CMAKE_CXX_COMPILER}")
endif(WITH_CCACHE AND CCACHE_FOUND)

set(ROCKSDB_AR "${CMAKE_AR}")

# we use an external project and copy the sources to bin directory to ensure
# that object files are built outside of the source tree.
include(ExternalProject)
ExternalProject_Add(rocksdb_ext
    URL "${CMAKE_SOURCE_DIR}/src/rocksdb"
    PREFIX "external"
    PATCH_COMMAND ""
    UPDATE_COMMAND ""
    CONFIGURE_COMMAND ""
    BUILD_COMMAND PORTABLE=1 ${ROCKSDB_JEMALLOC} $(MAKE) CXX=${ROCKSDB_CXX} AR=${ROCKSDB_AR} EXTRA_CXXFLAGS=${ROCKSDB_EXTRA_CXXFLAG} static_lib
    BUILD_IN_SOURCE 1
    INSTALL_COMMAND "")

# force rocksdb make to be called on each time
ExternalProject_Add_Step(rocksdb_ext forcebuild DEPENDEES configure DEPENDERS build ALWAYS 1)

ExternalProject_Get_Property(rocksdb_ext source_dir)
set(ROCKSDB_INCLUDE_DIR ${source_dir}/include)

# add a imported library for librocksdb.a
add_library(rocksdb STATIC IMPORTED)
add_dependencies(rocksdb rocksdb_ext)
set_property(TARGET rocksdb PROPERTY IMPORTED_LOCATION "${source_dir}/librocksdb.a")