3rdparty: libprotobuf v3.1.0

modules/dnn/3rdparty/protobuf/CMakeLists.txt

 project(libprotobuf)
 
 include(CheckIncludeFiles)
-include(cmake/CheckCxxHashset.cmake)
-include(cmake/CheckCxxHashmap.cmake)
 
-check_include_files("pthread.h" HAVE_PTHREAD)
-
-if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID STREQUAL "Clang")
-  include(CheckIncludeFileCXX)
-  set(CMAKE_REQUIRED_FLAGS "-std=c++11")
-  check_include_file_cxx("unordered_map" HAVE_UNORDERED_MAP)
-  check_include_file_cxx("tr1/unordered_map" HAVE_TR1_UNORDERED_MAP)
-  set(CMAKE_REQUIRED_FLAGS )
-
-  if(HAVE_UNORDERED_MAP)
-    add_definitions("-std=c++11") # For unordered_map
-    set(HASH_MAP_H "<unordered_map>")
-    set(HASH_MAP_CLASS "unordered_map")
-    set(HASH_NAMESPACE "std")
-    set(HAVE_HASH_MAP 1)
-  elseif(HAVE_TR1_UNORDERED_MAP)
-    add_definitions("-std=c++11") # For unordered_map
-    set(HASH_MAP_H "<tr1/unordered_map>")
-    set(HASH_MAP_CLASS "unordered_map")
-    set(HASH_NAMESPACE "std::tr1")
-    set(HAVE_HASH_MAP 1)
-  else()
-    CHECK_HASHMAP()
-    if(HAVE_GNU_EXT_HASH_MAP)
-      set(HASH_MAP_H "<ext/hash_map>")
-      set(HASH_NAMESPACE "__gnu_cxx")
-      set(HASH_MAP_CLASS "hash_map")
-      set(HAVE_HASH_MAP 1)
-    elseif(HAVE_STD_EXT_HASH_MAP)
-      set(HASH_MAP_H "<ext/hash_map>")
-      set(HASH_NAMESPACE "std")
-      set(HASH_MAP_CLASS "hash_map")
-      set(HAVE_HASH_MAP 1)
-    elseif(HAVE_GLOBAL_HASH_MAP)
-      set(HASH_MAP_H "<ext/hash_map>")
-      set(HASH_NAMESPACE "")
-      set(HASH_MAP_CLASS "hash_map")
-      set(HAVE_HASH_MAP 1)
-    else()
-      set(HAVE_HASH_MAP 0)
-    endif()
-  endif()
-
-  set(CMAKE_REQUIRED_FLAGS "-std=c++11")
-  check_include_file_cxx("unordered_set" HAVE_UNORDERED_SET)
-  check_include_file_cxx("tr1/unordered_set" HAVE_TR1_UNORDERED_SET)
-  set(CMAKE_REQUIRED_FLAGS )
-
-  if(HAVE_UNORDERED_SET)
-    set(HASH_SET_H "<unordered_set>")
-    set(HASH_SET_CLASS "unordered_set")
-    set(HAVE_HASH_SET 1)
-  elseif(HAVE_TR1_UNORDERED_SET)
-    add_definitions("-std=c++11")
-    set(HASH_SET_H "<tr1/unordered_set>")
-    set(HASH_SET_CLASS "unordered_set")
-    set(HAVE_HASH_SET 1)
-  else()
-    CHECK_HASHSET()
-    if(HAVE_GNU_EXT_HASH_SET)
-      set(HASH_SET_H "<ext/hash_set>")
-      set(HASH_NAMESPACE "__gnu_cxx")
-      set(HASH_SET_CLASS "hash_set")
-      set(HAVE_HASH_SET 1)
-    elseif(HAVE_STD_EXT_HASH_SET)
-      set(HASH_SET_H "<ext/hash_set>")
-      set(HASH_NAMESPACE "std")
-      set(HASH_SET_CLASS "hash_set")
-      set(HAVE_HASH_SET 1)
-    elseif(HAVE_GLOBAL_HASH_SET)
-      set(HASH_SET_H "<hash_set>")
-      set(HASH_NAMESPACE "")
-      set(HASH_SET_CLASS "hash_set")
-      set(HAVE_HASH_SET 1)
-    else()
-      set(HAVE_HASH_SET 0)
-    endif()
+if(NOT MSVC)
+  check_include_files("pthread.h" HAVE_PTHREAD)
+  if(HAVE_PTHREAD)
+    add_definitions(-DHAVE_PTHREAD=1)
   endif()
 endif()
 
-if(WIN32 AND BUILD_SHARED_LIBS AND MSVC)
-    add_definitions(-DPROTOBUF_USE_DLLS)
-    add_definitions(-DLIBPROTOBUF_EXPORTS)
-endif()
-
-#add_definitions( -DGOOGLE_PROTOBUF_NO_THREAD_SAFETY ) #we don't need thread safety
-add_definitions( -D_GNU_SOURCE=1 ) #it's maybe useful
-add_definitions( -DHAVE_CONFIG_H ) #we will use config.h
-configure_file("cmake/config.h.in" "config.h")
-
 if(MSVC)
   add_definitions( -D_CRT_SECURE_NO_WARNINGS=1 )
-  ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4244 /wd4267 /wd4018 /wd4355 /wd4800 /wd4251 /wd4996 /wd4146 /wd4305 /wd4127 /wd4100 /wd4512 /wd4125 /wd4389 /wd4510 /wd4610 /wd4702)
-  ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4456) # VS 2015
+  ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4244 /wd4267 /wd4018 /wd4355 /wd4800 /wd4251 /wd4996 /wd4146
+                                       /wd4305 /wd4127 /wd4100 /wd4512 /wd4125 /wd4389 /wd4510 /wd4610
+                                       /wd4702 /wd4456 /wd4457 /wd4065 /wd4310 /wd4661 /wd4506
+  )
 else()
-  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wno-deprecated -Wmissing-prototypes -Wmissing-declarations -Wshadow -Wunused-parameter -Wunused-local-typedefs -Wsign-compare -Wsign-promo -Wundef)
-  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wtautological-undefined-compare)
+  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wno-deprecated -Wmissing-prototypes -Wmissing-declarations -Wshadow -Wunused-parameter -Wunused-local-typedefs -Wsign-compare -Wsign-promo -Wundef
+                                       -Wtautological-undefined-compare
+                                       -Wignored-qualifiers -Wextra -Wunused-function -Wunused-const-variable
+  )
 endif()
 
 # Easier to support different versions of protobufs
@@ -116,7 +35,7 @@ function(append_if_exist OUTPUT_LIST)
     set(${OUTPUT_LIST} ${${OUTPUT_LIST}} PARENT_SCOPE)
 endfunction()
 
-set(PROTOBUF_ROOT ${CMAKE_CURRENT_SOURCE_DIR})
+set(PROTOBUF_ROOT ${CMAKE_CURRENT_SOURCE_DIR}/sources/protobuf-3.1.0)
 
 if(MSVC)
   set(ATOMICOPS_INTERNALS ${PROTOBUF_ROOT}/src/google/protobuf/stubs/atomicops_internals_x86_msvc.cc)
@@ -124,61 +43,103 @@ else()
   set(ATOMICOPS_INTERNALS ${PROTOBUF_ROOT}/src/google/protobuf/stubs/atomicops_internals_x86_gcc.cc)
 endif()
 
+
 append_if_exist(PROTOBUF_SRCS
-  ${PROTOBUF_ROOT}/src/google/protobuf/compiler/importer.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/compiler/parser.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/descriptor.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/descriptor.pb.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/descriptor_database.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/dynamic_message.cc
+# libprotobuf-lite
+  ${PROTOBUF_ROOT}/src/google/protobuf/arena.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/arenastring.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/extension_set.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/extension_set_heavy.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/generated_message_reflection.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/generated_message_util.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/io/coded_stream.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/io/gzip_stream.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/io/printer.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/io/tokenizer.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/io/zero_copy_stream.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/io/zero_copy_stream_impl.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/io/zero_copy_stream_impl_lite.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/message.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/message_lite.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/reflection_ops.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/repeated_field.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/service.cc
   ${ATOMICOPS_INTERNALS}
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/bytestream.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/stubs/common.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/int128.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/stubs/once.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/status.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/statusor.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/stringpiece.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/stubs/stringprintf.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/stubs/structurally_valid.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/stubs/strutil.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/time.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/wire_format_lite.cc
+# libprotobuf
+  ${PROTOBUF_ROOT}/src/google/protobuf/any.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/any.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/api.pb.cc
+#  ${PROTOBUF_ROOT}/src/google/protobuf/compiler/importer.cc
+#  ${PROTOBUF_ROOT}/src/google/protobuf/compiler/parser.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/descriptor.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/descriptor.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/descriptor_database.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/duration.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/dynamic_message.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/empty.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/extension_set_heavy.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/field_mask.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/generated_message_reflection.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/io/gzip_stream.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/io/printer.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/io/strtod.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/io/tokenizer.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/io/zero_copy_stream_impl.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/map_field.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/message.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/reflection_ops.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/service.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/source_context.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/struct.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/stubs/mathlimits.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/stubs/substitute.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/text_format.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/timestamp.pb.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/type.pb.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/unknown_field_set.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/field_comparator.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/field_mask_util.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/datapiece.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/default_value_objectwriter.cc
+#  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/error_listener.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/field_mask_utility.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/json_escaping.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/json_objectwriter.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/json_stream_parser.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/object_writer.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/proto_writer.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/protostream_objectsource.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/protostream_objectwriter.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/type_info.cc
+#  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/type_info_test_helper.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/internal/utility.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/json_util.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/message_differencer.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/time_util.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/util/type_resolver_util.cc
   ${PROTOBUF_ROOT}/src/google/protobuf/wire_format.cc
-  ${PROTOBUF_ROOT}/src/google/protobuf/wire_format_lite.cc
-  #${PROTOBUF_ROOT}/src/google/protobuf/stubs/hash.cc
+  ${PROTOBUF_ROOT}/src/google/protobuf/wrappers.pb.cc
 )
 
-if(UNIX AND (CMAKE_COMPILER_IS_GNUCXX OR CV_ICC))
+if(CMAKE_VERSION VERSION_LESS 2.8.9 AND UNIX)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
 endif()
 
 add_library(libprotobuf STATIC ${PROTOBUF_SRCS})
-include_directories(${PROTOBUF_ROOT}/src ${CMAKE_CURRENT_BINARY_DIR})
+include_directories(${PROTOBUF_ROOT}/src)
 
 set_target_properties(libprotobuf
     PROPERTIES
+    FOLDER "3rdparty"
+    POSITION_INDEPENDENT_CODE 1    # CMake 2.8.9+
     OUTPUT_NAME libprotobuf
     DEBUG_POSTFIX "${OPENCV_DEBUG_POSTFIX}"
     ARCHIVE_OUTPUT_DIRECTORY ${3P_LIBRARY_OUTPUT_PATH}
     )
 
-if(ENABLE_SOLUTION_FOLDERS)
-  set_target_properties(libprotobuf PROPERTIES FOLDER "3rdparty")
-endif()
-
 if(NOT BUILD_SHARED_LIBS)
   ocv_install_target(libprotobuf EXPORT OpenCVModules ARCHIVE DESTINATION ${OPENCV_3P_LIB_INSTALL_PATH} COMPONENT dev)
 endif()

modules/dnn/CMakeLists.txt

@@ -10,8 +10,10 @@ set(the_description "Deep neural network module. It allows to load models from d
 set(OPENCV_MODULE_IS_PART_OF_WORLD OFF)
 
 ocv_add_module(dnn opencv_core opencv_imgproc WRAP python matlab)
-ocv_warnings_disable(CMAKE_CXX_FLAGS -Wno-shadow -Wno-parentheses -Wmaybe-uninitialized -Wsign-promo -Wmissing-declarations -Wmissing-prototypes)
-ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4701)
+ocv_warnings_disable(CMAKE_CXX_FLAGS -Wno-shadow -Wno-parentheses -Wmaybe-uninitialized -Wsign-promo
+                                     -Wmissing-declarations -Wmissing-prototypes
+)
+ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4701 /wd4100)
 
 # ----------------------------------------------------------------------------
 # Resolve libprotobuf dependency

modules/dnn/cmake/OpenCVFindLibProtobuf.cmake

-OCV_OPTION(BUILD_LIBPROTOBUF_FROM_SOURCES "Force to build libprotobuf from sources (don't try to find it in system)" OFF)
+# By default, we use built-in protobuf sources and pre-generated .proto files
+# Note: In case of .proto model updates these variables should be used:
+# - PROTOBUF_PROTOC_EXECUTABLE (required)
+# - PROTOBUF_INCLUDE_DIR
+# - PROTOBUF_LIBRARIES or PROTOBUF_LIBRARY / PROTOBUF_LIBRARY_DEBUG for find_package()
+OCV_OPTION(BUILD_PROTOBUF "Force to build libprotobuf from sources" ON)
+OCV_OPTION(UPDATE_PROTO_FILES "Force to rebuild .proto files" OFF)
 
-if(NOT BUILD_LIBPROTOBUF_FROM_SOURCES)
-  find_package(Protobuf)
-endif()
-
-if(NOT BUILD_LIBPROTOBUF_FROM_SOURCES AND PROTOBUF_FOUND AND EXISTS ${PROTOBUF_PROTOC_EXECUTABLE})
-  message(STATUS "The protocol buffer compiler and libprotobuf were found")
-  PROTOBUF_GENERATE_CPP(PROTOBUF_HDRS PROTOBUF_SRCS src/caffe/caffe.proto)
-  add_definitions(-DHAVE_PROTOBUF=1)
-else()
-  message(STATUS "Build libprotobuf from sources:")
-  if(NOT PROTOBUF_FOUND)
-  message(STATUS "    libprotobuf not found into system")
+if(UPDATE_PROTO_FILES)
+  if(NOT DEFINED PROTOBUF_PROTOC_EXECUTABLE)
+    find_package(Protobuf QUIET)
   endif()
-  if(NOT EXISTS ${PROTOBUF_PROTOC_EXECUTABLE})
-  message(STATUS "    The protocol buffer compiler not found")
+  if(DEFINED PROTOBUF_PROTOC_EXECUTABLE AND EXISTS ${PROTOBUF_PROTOC_EXECUTABLE})
+    message(STATUS "The protocol buffer compiler is found (${PROTOBUF_PROTOC_EXECUTABLE})")
+    PROTOBUF_GENERATE_CPP(PROTOBUF_HDRS PROTOBUF_SRCS
+        src/caffe/caffe.proto
+    )
+  else()
+    message(FATAL_ERROR "The protocol buffer compiler is not found (PROTOBUF_PROTOC_EXECUTABLE='${PROTOBUF_PROTOC_EXECUTABLE}')")
   endif()
+endif()
 
-  #take into account OpenCV two-pass module addition scheme
-  if(NOT OPENCV_INITIAL_PASS) #TODO: it looks like a hack
-  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/protobuf)
-  endif()
+if(NOT BUILD_PROTOBUF AND NOT (DEFINED PROTOBUF_INCLUDE_DIR AND DEFINED PROTOBUF_LIBRARIES))
+  find_package(Protobuf QUIET)
+endif()
 
+if(PROTOBUF_FOUND)
+  # nothing
+else()
+  include(${CMAKE_CURRENT_LIST_DIR}/download_protobuf.cmake)
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/protobuf)
   set(PROTOBUF_LIBRARIES libprotobuf)
-  set(PROTOBUF_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/protobuf/src ${CMAKE_CURRENT_SOURCE_DIR}/misc/caffe)
-  set(PROTOBUF_SRCS ${CMAKE_CURRENT_SOURCE_DIR}/misc/caffe/caffe.pb.cc)
-  set(PROTOBUF_HDRS ${CMAKE_CURRENT_SOURCE_DIR}/misc/caffe/caffe.pb.h)
-  add_definitions(-DHAVE_PROTOBUF=1)
+  set(PROTOBUF_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/protobuf/sources/protobuf-3.1.0/src)
+endif()
 
-  #supress warnings in autogenerated caffe.pb.* files
-  ocv_warnings_disable(CMAKE_CXX_FLAGS -Wunused-parameter)
-  ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4125 /wd4267 /wd4127 /wd4244 /wd4512 /wd4702)
+if(NOT UPDATE_PROTO_FILES)
+  list(APPEND PROTOBUF_SRCS ${CMAKE_CURRENT_SOURCE_DIR}/misc/caffe/caffe.pb.cc)
+  list(APPEND PROTOBUF_HDRS ${CMAKE_CURRENT_SOURCE_DIR}/misc/caffe/caffe.pb.h)
+  list(APPEND PROTOBUF_INCLUDE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/misc/caffe)
 endif()
+
+add_definitions(-DHAVE_PROTOBUF=1)
+
+#supress warnings in autogenerated caffe.pb.* files
+ocv_warnings_disable(CMAKE_CXX_FLAGS -Wunused-parameter -Wundef)
+ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4125 /wd4267 /wd4127 /wd4244 /wd4512 /wd4702)

modules/dnn/cmake/download_protobuf.cmake

+set(PROTOBUF_CPP_NAME "libprotobuf")
+set(PROTOBUF_CPP_DOWNLOAD_HASH "bd5e3eed635a8d32e2b99658633815ef")
+set(PROTOBUF_CPP_PATH "${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/protobuf/sources") # /protobuf-3.1.0 subdirectory
+
+set(OPENCV_PROTOBUF_CPP_DOWNLOAD_URL ${OPENCV_PROTOBUF_URL};$ENV{OPENCV_PROTOBUF_URL};https://github.com/google/protobuf/releases/download/)
+
+function(ocv_protobuf_download file ID)
+  if(DEFINED ${ID}_DOWNLOADED_HASH
+       AND ${ID}_DOWNLOADED_HASH STREQUAL ${ID}_DOWNLOAD_HASH
+       AND EXISTS ${${ID}_PATH})
+    # Files have been downloaded and checked by the previous CMake run
+    return()
+  else()
+    if(EXISTS ${${ID}_PATH})
+      message(STATUS "${${ID}_NAME}: Removing previous unpacked files: ${${ID}_PATH}")
+      file(REMOVE_RECURSE ${${ID}_PATH})
+    endif()
+  endif()
+  unset(${ID}_DOWNLOADED_HASH CACHE)
+
+  file(MAKE_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/.download)
+  file(WRITE "${CMAKE_CURRENT_SOURCE_DIR}/.download/.gitignore" "*\n")
+  ocv_download(PACKAGE ${file}
+               HASH ${${ID}_DOWNLOAD_HASH}
+               URL ${OPENCV_${ID}_DOWNLOAD_URL}
+               DOWNLOAD_DIR ${CMAKE_CURRENT_SOURCE_DIR}/.download)
+  set(${ID}_ARCHIVE "${DOWNLOAD_PACKAGE_LOCATION}")
+
+  ocv_assert(EXISTS "${${ID}_ARCHIVE}")
+  ocv_assert(NOT EXISTS "${${ID}_PATH}")
+  file(MAKE_DIRECTORY ${${ID}_PATH})
+  ocv_assert(EXISTS "${${ID}_PATH}")
+  file(WRITE "${${ID}_PATH}/.gitignore" "*\n")
+
+  message(STATUS "${${ID}_NAME}: Unpacking ${file} to ${${ID}_PATH}...")
+  execute_process(COMMAND ${CMAKE_COMMAND} -E tar xz "${${ID}_ARCHIVE}"
+                  WORKING_DIRECTORY "${${ID}_PATH}"
+                  RESULT_VARIABLE __result)
+
+  if(NOT __result EQUAL 0)
+    message(FATAL_ERROR "${${ID}_NAME}: Failed to unpack ${ID} archive from ${${ID}_ARCHIVE} to ${${ID}_PATH} with error ${__result}")
+  endif()
+
+  ocv_assert(EXISTS "${${ID}_PATH}")
+
+  set(${ID}_DOWNLOADED_HASH "${${ID}_DOWNLOAD_HASH}" CACHE INTERNAL "${ID} hash")
+
+  #message(STATUS "${${ID}_NAME}: Successfully downloaded")
+endfunction()
+
+ocv_protobuf_download(v3.1.0/protobuf-cpp-3.1.0.tar.gz PROTOBUF_CPP)