text: # Ceres Solver - A fast non-linear least squares minimizer
  # Copyright 2015 Google Inc. All rights reserved.
  # http://ceres-solver.org/
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions are met:
  #
  # * Redistributions of source code must retain the above copyright notice,
  #   this list of conditions and the following disclaimer.
  # * Redistributions in binary form must reproduce the above copyright notice,
  #   this list of conditions and the following disclaimer in the documentation
  #   and/or other materials provided with the distribution.
  # * Neither the name of Google Inc. nor the names of its contributors may be
  #   used to endorse or promote products derived from this software without
  #   specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  # AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  # ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  # LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  # INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  # CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  #
  # Author: alexs.mac@gmail.com (Alex Stewart)
  #
  
  # FindGlog.cmake - Find Google glog logging library.
  #
  # This module defines the following variables:
  #
  # GLOG_FOUND: TRUE iff glog is found.
  # GLOG_INCLUDE_DIRS: Include directories for glog.
  # GLOG_LIBRARIES: Libraries required to link glog.
  #
  # The following variables control the behaviour of this module:
  #
  # GLOG_INCLUDE_DIR_HINTS: List of additional directories in which to
  #                         search for glog includes, e.g: /timbuktu/include.
  # GLOG_LIBRARY_DIR_HINTS: List of additional directories in which to
  #                         search for glog libraries, e.g: /timbuktu/lib.
  #
  # The following variables are also defined by this module, but in line with
  # CMake recommended FindPackage() module style should NOT be referenced directly
  # by callers (use the plural variables detailed above instead).  These variables
  # do however affect the behaviour of the module via FIND_[PATH/LIBRARY]() which
  # are NOT re-called (i.e. search for library is not repeated) if these variables
  # are set with valid values _in the CMake cache_. This means that if these
  # variables are set directly in the cache, either by the user in the CMake GUI,
  # or by the user passing -DVAR=VALUE directives to CMake when called (which
  # explicitly defines a cache variable), then they will be used verbatim,
  # bypassing the HINTS variables and other hard-coded search locations.
  #
  # GLOG_INCLUDE_DIR: Include directory for glog, not including the
  #                   include directory of any dependencies.
  # GLOG_LIBRARY: glog library, not including the libraries of any
  #               dependencies.
  
  # Reset CALLERS_CMAKE_FIND_LIBRARY_PREFIXES to its value when
  # FindGlog was invoked.
  macro(GLOG_RESET_FIND_LIBRARY_PREFIX)
    if (MSVC)
      set(CMAKE_FIND_LIBRARY_PREFIXES "${CALLERS_CMAKE_FIND_LIBRARY_PREFIXES}")
    endif (MSVC)
  endmacro(GLOG_RESET_FIND_LIBRARY_PREFIX)
  
  # Called if we failed to find glog or any of it's required dependencies,
  # unsets all public (designed to be used externally) variables and reports
  # error message at priority depending upon [REQUIRED/QUIET/<NONE>] argument.
  macro(GLOG_REPORT_NOT_FOUND REASON_MSG)
    unset(GLOG_FOUND)
    unset(GLOG_INCLUDE_DIRS)
    unset(GLOG_LIBRARIES)
    # Make results of search visible in the CMake GUI if glog has not
    # been found so that user does not have to toggle to advanced view.
    mark_as_advanced(CLEAR GLOG_INCLUDE_DIR
                           GLOG_LIBRARY)
  
    glog_reset_find_library_prefix()
  
    # Note <package>_FIND_[REQUIRED/QUIETLY] variables defined by FindPackage()
    # use the camelcase library name, not uppercase.
    if (Glog_FIND_QUIETLY)
      message(STATUS "Failed to find glog - " ${REASON_MSG} ${ARGN})
    elseif (Glog_FIND_REQUIRED)
      message(FATAL_ERROR "Failed to find glog - " ${REASON_MSG} ${ARGN})
    else()
      # Neither QUIETLY nor REQUIRED, use no priority which emits a message
      # but continues configuration and allows generation.
      message("-- Failed to find glog - " ${REASON_MSG} ${ARGN})
    endif ()
  endmacro(GLOG_REPORT_NOT_FOUND)
  
  # Handle possible presence of lib prefix for libraries on MSVC, see
  # also GLOG_RESET_FIND_LIBRARY_PREFIX().
  if (MSVC)
    # Preserve the caller's original values for CMAKE_FIND_LIBRARY_PREFIXES
    # s/t we can set it back before returning.
    set(CALLERS_CMAKE_FIND_LIBRARY_PREFIXES "${CMAKE_FIND_LIBRARY_PREFIXES}")
    # The empty string in this list is important, it represents the case when
    # the libraries have no prefix (shared libraries / DLLs).
    set(CMAKE_FIND_LIBRARY_PREFIXES "lib" "" "${CMAKE_FIND_LIBRARY_PREFIXES}")
  endif (MSVC)
  
  # Search user-installed locations first, so that we prefer user installs
  # to system installs where both exist.
  list(APPEND GLOG_CHECK_INCLUDE_DIRS
    /usr/local/include
    /usr/local/homebrew/include # Mac OS X
    /opt/local/var/macports/software # Mac OS X.
    /opt/local/include
    /usr/include)
  # Windows (for C:/Program Files prefix).
  list(APPEND GLOG_CHECK_PATH_SUFFIXES
    glog/include
    glog/Include
    Glog/include
    Glog/Include)
  
  list(APPEND GLOG_CHECK_LIBRARY_DIRS
    /usr/local/lib
    /usr/local/homebrew/lib # Mac OS X.
    /opt/local/lib
    /usr/lib)
  # Windows (for C:/Program Files prefix).
  list(APPEND GLOG_CHECK_LIBRARY_SUFFIXES
    glog/lib
    glog/Lib
    Glog/lib
    Glog/Lib)
  
  # Search supplied hint directories first if supplied.
  find_path(GLOG_INCLUDE_DIR
    NAMES glog/logging.h
    PATHS ${GLOG_INCLUDE_DIR_HINTS}
    ${GLOG_CHECK_INCLUDE_DIRS}
    PATH_SUFFIXES ${GLOG_CHECK_PATH_SUFFIXES})
  if (NOT GLOG_INCLUDE_DIR OR
      NOT EXISTS ${GLOG_INCLUDE_DIR})
    glog_report_not_found(
      "Could not find glog include directory, set GLOG_INCLUDE_DIR "
      "to directory containing glog/logging.h")
  endif (NOT GLOG_INCLUDE_DIR OR
         NOT EXISTS ${GLOG_INCLUDE_DIR})
  
  find_library(GLOG_LIBRARY NAMES glog
    PATHS ${GLOG_LIBRARY_DIR_HINTS}
    ${GLOG_CHECK_LIBRARY_DIRS}
    PATH_SUFFIXES ${GLOG_CHECK_LIBRARY_SUFFIXES})
  if (NOT GLOG_LIBRARY OR
      NOT EXISTS ${GLOG_LIBRARY})
    glog_report_not_found(
      "Could not find glog library, set GLOG_LIBRARY "
      "to full path to libglog.")
  endif (NOT GLOG_LIBRARY OR
         NOT EXISTS ${GLOG_LIBRARY})
  
  # Mark internally as found, then verify. GLOG_REPORT_NOT_FOUND() unsets
  # if called.
  set(GLOG_FOUND TRUE)
  
  # Glog does not seem to provide any record of the version in its
  # source tree, thus cannot extract version.
  
  # Catch case when caller has set GLOG_INCLUDE_DIR in the cache / GUI and
  # thus FIND_[PATH/LIBRARY] are not called, but specified locations are
  # invalid, otherwise we would report the library as found.
  if (GLOG_INCLUDE_DIR AND
      NOT EXISTS ${GLOG_INCLUDE_DIR}/glog/logging.h)
    glog_report_not_found(
      "Caller defined GLOG_INCLUDE_DIR:"
      " ${GLOG_INCLUDE_DIR} does not contain glog/logging.h header.")
  endif (GLOG_INCLUDE_DIR AND
         NOT EXISTS ${GLOG_INCLUDE_DIR}/glog/logging.h)
  # TODO: This regex for glog library is pretty primitive, we use lowercase
  #       for comparison to handle Windows using CamelCase library names, could
  #       this check be better?
  string(TOLOWER "${GLOG_LIBRARY}" LOWERCASE_GLOG_LIBRARY)
  if (GLOG_LIBRARY AND
      NOT "${LOWERCASE_GLOG_LIBRARY}" MATCHES ".*glog[^/]*")
    glog_report_not_found(
      "Caller defined GLOG_LIBRARY: "
      "${GLOG_LIBRARY} does not match glog.")
  endif (GLOG_LIBRARY AND
         NOT "${LOWERCASE_GLOG_LIBRARY}" MATCHES ".*glog[^/]*")
  
  # Set standard CMake FindPackage variables if found.
  if (GLOG_FOUND)
    set(GLOG_INCLUDE_DIRS ${GLOG_INCLUDE_DIR})
    set(GLOG_LIBRARIES ${GLOG_LIBRARY})
  endif (GLOG_FOUND)
  
  glog_reset_find_library_prefix()
  
  # Handle REQUIRED / QUIET optional arguments.
  include(FindPackageHandleStandardArgs)
  find_package_handle_standard_args(Glog DEFAULT_MSG
    GLOG_INCLUDE_DIRS GLOG_LIBRARIES)
  
  # Only mark internal variables as advanced if we found glog, otherwise
  # leave them visible in the standard GUI for the user to set manually.
  if (GLOG_FOUND)
    mark_as_advanced(FORCE GLOG_INCLUDE_DIR
                           GLOG_LIBRARY)
  endif (GLOG_FOUND)
  