Merge pull request OSGeo#3711 from mwtoews/proj-db-cache-dir

CMake: add PROJ_DB_CACHE_DIR

Author: rouault

data/CMakeLists.txt

@@ -2,6 +2,15 @@
 # files containing dictionary of useful projection
 #
 
+set(PROJ_DB_CACHE_DIR "" CACHE PATH "Directory used to cache proj.db")
+if(NOT IS_DIRECTORY ${PROJ_DB_CACHE_DIR})
+  if(NOT "${PROJ_DB_CACHE_DIR}" STREQUAL "")
+    message(WARNING
+      "PROJ_DB_CACHE_DIR (${PROJ_DB_CACHE_DIR}) not set to a directory")
+    set(PROJ_DB_CACHE_DIR "")
+  endif()
+endif()
+
 set(CONFIG_FILES
   proj.ini
 )
@@ -36,7 +45,7 @@ include(sql_filelist.cmake)
 add_custom_command(
   OUTPUT ${PROJ_DB}
   COMMAND ${CMAKE_COMMAND} -E remove -f ${PROJ_DB}
-  COMMAND ${CMAKE_COMMAND} "-DALL_SQL_IN=${ALL_SQL_IN}" "-DEXE_SQLITE3=${EXE_SQLITE3}" "-DPROJ_DB=${PROJ_DB}" "-DPROJ_VERSION=${PROJ_VERSION}"
+  COMMAND ${CMAKE_COMMAND} "-DALL_SQL_IN=${ALL_SQL_IN}" "-DEXE_SQLITE3=${EXE_SQLITE3}" "-DPROJ_DB=${PROJ_DB}" "-DPROJ_VERSION=${PROJ_VERSION}" "-DPROJ_DB_CACHE_DIR=${PROJ_DB_CACHE_DIR}"
     -P "${CMAKE_CURRENT_SOURCE_DIR}/generate_proj_db.cmake"
   COMMAND ${CMAKE_COMMAND} -E copy ${PROJ_DB} ${CMAKE_CURRENT_BINARY_DIR}/for_tests
   DEPENDS ${SQL_FILES} "${CMAKE_CURRENT_SOURCE_DIR}/generate_proj_db.cmake"

data/generate_proj_db.cmake

@@ -14,10 +14,30 @@ file(READ ${ALL_SQL_IN} CONTENTS)
 string(REPLACE "\${PROJ_VERSION}" "${PROJ_VERSION}" CONTENTS_MOD "${CONTENTS}")
 file(WRITE "${ALL_SQL_IN}" "${CONTENTS_MOD}")
 
+if(IS_DIRECTORY ${PROJ_DB_CACHE_DIR})
+  set(USE_PROJ_DB_CACHE_DIR TRUE)
+  set(PROJ_DB_SQL_MD5_FILE "${PROJ_DB_CACHE_DIR}/proj.db.sql.md5")
+  if(EXISTS "${PROJ_DB_SQL_MD5_FILE}")
+    file(STRINGS "${PROJ_DB_SQL_MD5_FILE}" PROJ_DB_SQL_MD5 LIMIT_COUNT 1)
+  endif()
+  file(MD5 "${ALL_SQL_IN}" PROJ_DB_SQL_MD5)
+  set(CACHED_PROJ_DB "${PROJ_DB_CACHE_DIR}/proj.db")
+  if("${PROJ_DB_SQL_MD5}" STREQUAL "${PROJ_DB_SQL_MD5}" AND EXISTS "${CACHED_PROJ_DB}")
+    message(STATUS "Reusing cached proj.db from ${PROJ_DB_CACHE_DIR}")
+    get_filename_component(PROJ_DB_DIR "${PROJ_DB}" DIRECTORY)
+    file(COPY "${CACHED_PROJ_DB}" DESTINATION "${PROJ_DB_DIR}")
+    return()
+  endif()
+endif()
+
 execute_process(COMMAND "${EXE_SQLITE3}" "${PROJ_DB}"
                 INPUT_FILE "${ALL_SQL_IN}"
                 RESULT_VARIABLE STATUS)
 
 if(STATUS AND NOT STATUS EQUAL 0)
-  message(FATAL_ERROR "SQLite3 failed")
+  message(FATAL_ERROR "Build of proj.db failed")
+elseif(USE_PROJ_DB_CACHE_DIR)
+  message(STATUS "Saving cache: ${CACHED_PROJ_DB}")
+  file(COPY "${PROJ_DB}" DESTINATION "${PROJ_DB_CACHE_DIR}")
+  file(WRITE "${PROJ_DB_SQL_MD5_FILE}" "${PROJ_DB_SQL_MD5}\n")
 endif()

docs/source/install.rst

@@ -371,6 +371,11 @@ All cached entries can be viewed using ``cmake -LAH`` from a build directory.
     `clcache <https://github.com/frerich/clcache>`_ for MSVC)
     to build C/C++ objects.
 
+.. option:: PROJ_DB_CACHE_DIR
+
+    Path to an existing directory used to cache :file:`proj.db` to speed-up
+    subsequent builds without modifications to source SQL files.
+
 
 Building on Windows with vcpkg and Visual Studio 2017 or 2019
 --------------------------------------------------------------------------------