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dnl @synopsis AX_LIB_EVENT([MINIMUM-VERSION])

dnl

dnl Test for the libevent library of a particular version (or newer).

dnl

dnl If no path to the installed libevent is given, the macro will first try

dnl using no -I or -L flags, then searches under /usr, /usr/local, /opt,

dnl and /opt/libevent.

dnl If these all fail, it will try the $LIBEVENT_ROOT environment variable.

dnl

dnl This macro requires that #include <sys/types.h> works and defines u_char.

dnl

dnl This macro calls:

dnl   AC_SUBST(LIBEVENT_CPPFLAGS)

dnl   AC_SUBST(LIBEVENT_LDFLAGS)

dnl   AC_SUBST(LIBEVENT_LIBS)

dnl

dnl And (if libevent is found):

dnl   AC_DEFINE(HAVE_LIBEVENT)

dnl

dnl It also leaves the shell variables "success" and "ax_have_libevent"

dnl set to "yes" or "no".

dnl

dnl NOTE: This macro does not currently work for cross-compiling,

dnl       but it can be easily modified to allow it.  (grep "cross").

dnl

dnl @category InstalledPackages

dnl @category C

dnl @version 2007-09-12

dnl @license AllPermissive

dnl

dnl Copyright (C) 2009 David Reiss

dnl Copying and distribution of this file, with or without modification,

dnl are permitted in any medium without royalty provided the copyright

dnl notice and this notice are preserved.

dnl Input: ax_libevent_path, WANT_LIBEVENT_VERSION

dnl Output: success=yes/no

AC_DEFUN([AX_LIB_EVENT_DO_CHECK],

         [

          # Save our flags.

          CPPFLAGS_SAVED="$CPPFLAGS"

          LDFLAGS_SAVED="$LDFLAGS"

          LIBS_SAVED="$LIBS"

          LD_LIBRARY_PATH_SAVED="$LD_LIBRARY_PATH"

          # Set our flags if we are checking a specific directory.

          if test -n "$ax_libevent_path" ; then

            LIBEVENT_CPPFLAGS="-I$ax_libevent_path/include"

            LIBEVENT_LDFLAGS="-L$ax_libevent_path/lib"

            LD_LIBRARY_PATH="$ax_libevent_path/lib:$LD_LIBRARY_PATH"

          else

            LIBEVENT_CPPFLAGS=""

            LIBEVENT_LDFLAGS=""

          fi

          # Required flag for libevent.

          LIBEVENT_LIBS="-levent"

          # Prepare the environment for compilation.

          CPPFLAGS="$CPPFLAGS $LIBEVENT_CPPFLAGS"

          LDFLAGS="$LDFLAGS $LIBEVENT_LDFLAGS"

          LIBS="$LIBS $LIBEVENT_LIBS"

          export CPPFLAGS

          export LDFLAGS

          export LIBS

          export LD_LIBRARY_PATH

          success=no

          # Compile, link, and run the program.  This checks:

          # - event.h is available for including.

          # - event_get_version() is available for linking.

          # - The event version string is lexicographically greater

          #   than the required version.

          AC_LANG_PUSH([C])

          dnl This can be changed to AC_LINK_IFELSE if you are cross-compiling,

          dnl but then the version cannot be checked.

          AC_RUN_IFELSE([AC_LANG_PROGRAM([[

          #include <sys/types.h>

          #include <event.h>

          ]], [[

          const char* lib_version = event_get_version();

          const char* wnt_version = "$WANT_LIBEVENT_VERSION";

          for (;;) {

            /* If we reached the end of the want version.  We have it. */

            if (*wnt_version == '\0' || *wnt_version == '-') {

              return 0;

            }

            /* If the want version continues but the lib version does not, */

            /* we are missing a letter.  We don't have it. */

            if (*lib_version == '\0' || *lib_version == '-') {

              return 1;

            }

            /* In the 1.4 version numbering style, if there are more digits */

            /* in one version than the other, that one is higher. */

            int lib_digits;

            for (lib_digits = 0;

                lib_version[lib_digits] >= '0' &&

                lib_version[lib_digits] <= '9';

                lib_digits++)

              ;

            int wnt_digits;

            for (wnt_digits = 0;

                wnt_version[wnt_digits] >= '0' &&

                wnt_version[wnt_digits] <= '9';

                wnt_digits++)

              ;

            if (lib_digits > wnt_digits) {

              return 0;

            }

            if (lib_digits < wnt_digits) {

              return 1;

            }

            /* If we have greater than what we want.  We have it. */

            if (*lib_version > *wnt_version) {

              return 0;

            }

            /* If we have less, we don't. */

            if (*lib_version < *wnt_version) {

              return 1;

            }

            lib_version++;

            wnt_version++;

          }

          return 0;

          ]])], [

          success=yes

          ])

          AC_LANG_POP([C])

          # Restore flags.

          CPPFLAGS="$CPPFLAGS_SAVED"

          LDFLAGS="$LDFLAGS_SAVED"

          LIBS="$LIBS_SAVED"

          LD_LIBRARY_PATH="$LD_LIBRARY_PATH_SAVED"

         ])

AC_DEFUN([AX_LIB_EVENT],

         [

          dnl Allow search path to be overridden on the command line.

          AC_ARG_WITH([libevent],

                      AS_HELP_STRING([--with-libevent@<:@=DIR@:>@], [use libevent (default is yes) - it is possible to specify an alternate root directory for libevent]),

                      [

                       if test "x$withval" = "xno"; then

                         want_libevent="no"

                       elif test "x$withval" = "xyes"; then

                         want_libevent="yes"

                         ax_libevent_path=""

                       else

                         want_libevent="yes"

                         ax_libevent_path="$withval"

                       fi

                       ],

                       [ want_libevent="yes" ; ax_libevent_path="" ])

          if test "$want_libevent" = "yes"; then

            WANT_LIBEVENT_VERSION=ifelse([$1], ,1.2,$1)

            AC_MSG_CHECKING(for libevent >= $WANT_LIBEVENT_VERSION)

            # Run tests.

            if test -n "$ax_libevent_path"; then

              AX_LIB_EVENT_DO_CHECK

            else

              for ax_libevent_path in "" /usr /usr/local /opt /opt/local /opt/libevent "$LIBEVENT_ROOT" ; do

                AX_LIB_EVENT_DO_CHECK

                if test "$success" = "yes"; then

                  break;

                fi

              done

            fi

            if test "$success" != "yes" ; then

              AC_MSG_RESULT(no)

              LIBEVENT_CPPFLAGS=""

              LIBEVENT_LDFLAGS=""

              LIBEVENT_LIBS=""

            else

              AC_MSG_RESULT(yes)

              AC_DEFINE(HAVE_LIBEVENT,,[define if libevent is available])

              ax_have_libevent_[]m4_translit([$1], [.], [_])="yes"

            fi

            ax_have_libevent="$success"

            AC_SUBST(LIBEVENT_CPPFLAGS)

            AC_SUBST(LIBEVENT_LDFLAGS)

            AC_SUBST(LIBEVENT_LIBS)

          fi

          ])