cmake: restore file FindCapnpProto.cmake

It is useful for autoconf based installations.

c++/cmake/FindCapnProto.cmake

+#
+# Finds the Cap'n Proto libraries, and compiles schema files.
+#
+# Configuration variables (optional):
+#   CAPNPC_OUTPUT_DIR
+#       Directory to place compiled schema sources (default: the same directory as the schema file).
+#   CAPNPC_IMPORT_DIRS
+#       List of additional include directories for the schema compiler.
+#       (CMAKE_CURRENT_SOURCE_DIR and CAPNP_INCLUDE_DIRS are always included.)
+#   CAPNPC_SRC_PREFIX
+#       Schema file source prefix (default: CMAKE_CURRENT_SOURCE_DIR).
+#   CAPNPC_FLAGS
+#       Additional flags to pass to the schema compiler.
+#
+# Variables that are discovered:
+#   CAPNP_EXECUTABLE
+#       Path to the `capnp` tool (can be set to override).
+#   CAPNPC_CXX_EXECUTABLE
+#       Path to the `capnpc-c++` tool (can be set to override).
+#   CAPNP_INCLUDE_DIRS
+#       Include directories for the library's headers (can be set to override).
+#   CANP_LIBRARIES
+#       The Cap'n Proto library paths.
+#   CAPNP_LIBRARIES_LITE
+#       Paths to only the 'lite' libraries.
+#   CAPNP_DEFINITIONS
+#       Compiler definitions required for building with the library.
+#   CAPNP_FOUND
+#       Set if the libraries have been located.
+#
+# Example usage:
+#
+#   find_package(CapnProto REQUIRED)
+#   include_directories(${CAPNP_INCLUDE_DIRS})
+#   add_definitions(${CAPNP_DEFINITIONS})
+#
+#   capnp_generate_cpp(CAPNP_SRCS CAPNP_HDRS schema.capnp)
+#   add_executable(a a.cc ${CAPNP_SRCS} ${CAPNP_HDRS})
+#   target_link_library(a ${CAPNP_LIBRARIES})
+#
+# For out-of-source builds:
+#
+#   set(CAPNPC_OUTPUT_DIR ${CMAKE_CURRENT_BINARY_DIR})
+#   include_directories(${CAPNPC_OUTPUT_DIR})
+#   capnp_generate_cpp(...)
+#
+
+# CAPNP_GENERATE_CPP ===========================================================
+
+function(CAPNP_GENERATE_CPP SOURCES HEADERS)
+  if(NOT ARGN)
+    message(SEND_ERROR "CAPNP_GENERATE_CPP() called without any source files.")
+  endif()
+  if(NOT CAPNP_EXECUTABLE)
+    message(SEND_ERROR "Could not locate capnp executable (CAPNP_EXECUTABLE).")
+  endif()
+  if(NOT CAPNPC_CXX_EXECUTABLE)
+    message(SEND_ERROR "Could not locate capnpc-c++ executable (CAPNPC_CXX_EXECUTABLE).")
+  endif()
+  if(NOT CAPNP_INCLUDE_DIRS)
+    message(SEND_ERROR "Could not locate capnp header files (CAPNP_INCLUDE_DIRS).")
+  endif()
+
+  # Default compiler includes
+  set(include_path -I ${CMAKE_CURRENT_SOURCE_DIR} -I ${CAPNP_INCLUDE_DIRS})
+
+  if(DEFINED CAPNPC_IMPORT_DIRS)
+    # Append each directory as a series of '-I' flags in ${include_path}
+    foreach(directory ${CAPNPC_IMPORT_DIRS})
+      get_filename_component(absolute_path "${directory}" ABSOLUTE)
+      list(APPEND include_path -I ${absolute_path})
+    endforeach()
+  endif()
+
+  if(DEFINED CAPNPC_OUTPUT_DIR)
+    # Prepend a ':' to get the format for the '-o' flag right
+    set(output_dir ":${CAPNPC_OUTPUT_DIR}")
+  else()
+    set(output_dir ":.")
+  endif()
+
+  if(NOT DEFINED CAPNPC_SRC_PREFIX)
+    set(CAPNPC_SRC_PREFIX "${CMAKE_CURRENT_SOURCE_DIR}")
+  endif()
+  get_filename_component(CAPNPC_SRC_PREFIX "${CAPNPC_SRC_PREFIX}" ABSOLUTE)
+
+  set(${SOURCES})
+  set(${HEADERS})
+  foreach(schema_file ${ARGN})
+    get_filename_component(file_path "${schema_file}" ABSOLUTE)
+    get_filename_component(file_dir "${file_path}" PATH)
+
+    # Figure out where the output files will go
+    if (NOT DEFINED CAPNPC_OUTPUT_DIR)
+      set(output_base "${file_path}")
+    else()
+      # Output files are placed in CAPNPC_OUTPUT_DIR, at a location as if they were
+      # relative to CAPNPC_SRC_PREFIX.
+      string(LENGTH "${CAPNPC_SRC_PREFIX}" prefix_len)
+      string(SUBSTRING "${file_path}" 0 ${prefix_len} output_prefix)
+      if(NOT "${CAPNPC_SRC_PREFIX}" STREQUAL "${output_prefix}")
+        message(SEND_ERROR "Could not determine output path for '${schema_file}' ('${file_path}') with source prefix '${CAPNPC_SRC_PREFIX}' into '${CAPNPC_OUTPUT_DIR}'.")
+      endif()
+
+      string(SUBSTRING "${file_path}" ${prefix_len} -1 output_path)
+      set(output_base "${CAPNPC_OUTPUT_DIR}${output_path}")
+    endif()
+
+    add_custom_command(
+      OUTPUT "${output_base}.c++" "${output_base}.h"
+      COMMAND "${CAPNP_EXECUTABLE}"
+      ARGS compile 
+          -o ${CAPNPC_CXX_EXECUTABLE}${output_dir}
+          --src-prefix ${CAPNPC_SRC_PREFIX}
+          ${include_path}
+          ${CAPNPC_FLAGS}
+          ${file_path}
+      DEPENDS "${schema_file}"
+      COMMENT "Compiling Cap'n Proto schema ${schema_file}"
+      VERBATIM
+    )
+    list(APPEND ${SOURCES} "${output_base}.c++")
+    list(APPEND ${HEADERS} "${output_base}.h")
+  endforeach()
+
+  set_source_files_properties(${${SOURCES}} ${${HEADERS}} PROPERTIES GENERATED TRUE)
+  set(${SOURCES} ${${SOURCES}} PARENT_SCOPE)
+  set(${HEADERS} ${${HEADERS}} PARENT_SCOPE)
+endfunction()
+
+# Find Libraries/Paths =========================================================
+
+# Use pkg-config to get path hints and definitions
+find_package(PkgConfig QUIET)
+pkg_check_modules(PKGCONFIG_CAPNP capnp)
+pkg_check_modules(PKGCONFIG_CAPNP_RPC capnp-rpc QUIET)
+pkg_check_modules(PKGCONFIG_CAPNP_JSON capnp-json QUIET)
+
+find_library(CAPNP_LIB_KJ kj
+  HINTS "${PKGCONFIG_CAPNP_LIBDIR}" ${PKGCONFIG_CAPNP_LIBRARY_DIRS}
+)
+find_library(CAPNP_LIB_KJ-ASYNC kj-async
+  HINTS "${PKGCONFIG_CAPNP_RPC_LIBDIR}" ${PKGCONFIG_CAPNP_RPC_LIBRARY_DIRS}
+)
+find_library(CAPNP_LIB_CAPNP capnp
+  HINTS "${PKGCONFIG_CAPNP_LIBDIR}" ${PKGCONFIG_CAPNP_LIBRARY_DIRS}
+)
+find_library(CAPNP_LIB_CAPNP-RPC capnp-rpc
+  HINTS "${PKGCONFIG_CAPNP_RPC_LIBDIR}" ${PKGCONFIG_CAPNP_RPC_LIBRARY_DIRS}
+)
+find_library(CAPNP_LIB_CAPNP-JSON capnp-json
+  HINTS "${PKGCONFIG_CAPNP_JSON_LIBDIR}" ${PKGCONFIG_CAPNP_JSON_LIBRARY_DIRS}
+)
+mark_as_advanced(CAPNP_LIB_KJ CAPNP_LIB_KJ-ASYNC CAPNP_LIB_CAPNP CAPNP_LIB_CAPNP-RPC CAPNP_LIB_CAPNP-JSON)
+set(CAPNP_LIBRARIES_LITE
+  ${CAPNP_LIB_CAPNP}
+  ${CAPNP_LIB_KJ}
+)
+set(CAPNP_LIBRARIES
+  ${CAPNP_LIB_CAPNP-JSON}
+  ${CAPNP_LIB_CAPNP-RPC}
+  ${CAPNP_LIB_CAPNP}
+  ${CAPNP_LIB_KJ-ASYNC}
+  ${CAPNP_LIB_KJ}
+)
+
+# Was only the 'lite' library found?
+if(CAPNP_LIB_CAPNP AND NOT CAPNP_LIB_CAPNP-RPC)
+  set(CAPNP_DEFINITIONS -DCAPNP_LITE)
+else()
+  set(CAPNP_DEFINITIONS)
+endif()
+
+find_path(CAPNP_INCLUDE_DIRS capnp/generated-header-support.h
+  HINTS "${PKGCONFIG_CAPNP_INCLUDEDIR}" ${PKGCONFIG_CAPNP_INCLUDE_DIRS}
+)
+
+find_program(CAPNP_EXECUTABLE
+  NAMES capnp
+  DOC "Cap'n Proto Command-line Tool"
+  HINTS "${PKGCONFIG_CAPNP_PREFIX}/bin"
+)
+
+find_program(CAPNPC_CXX_EXECUTABLE
+  NAMES capnpc-c++
+  DOC "Capn'n Proto C++ Compiler"
+  HINTS "${PKGCONFIG_CAPNP_PREFIX}/bin"
+)
+
+# Only *require* the include directory, libkj, and libcapnp. If compiling with
+# CAPNP_LITE, nothing else will be found.
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(CAPNP DEFAULT_MSG
+  CAPNP_INCLUDE_DIRS
+  CAPNP_LIB_KJ
+  CAPNP_LIB_CAPNP
+)