dnl @synopsis AX_LIB_ZLIB([MINIMUM-VERSION])
dnl
dnl Test for the libz library of a particular version (or newer).
dnl
dnl If no path to the installed zlib is given, the macro will first try
dnl using no -I or -L flags, then searches under /usr, /usr/local, /opt,
dnl and /opt/zlib.
dnl If these all fail, it will try the $ZLIB_ROOT environment variable.
dnl
dnl This macro calls:
dnl   AC_SUBST(ZLIB_CPPFLAGS)
dnl   AC_SUBST(ZLIB_LDFLAGS)
dnl   AC_SUBST(ZLIB_LIBS)
dnl
dnl And (if zlib is found):
dnl   AC_DEFINE(HAVE_ZLIB)
dnl
dnl It also leaves the shell variables "success" and "ax_have_zlib"
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 @author David Reiss <dreiss@facebook.com>
dnl @version 2007-09-12
dnl @license AllPermissive

dnl Input: ax_zlib_path, WANT_ZLIB_VERSION
dnl Output: success=yes/no
AC_DEFUN([AX_LIB_ZLIB_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 "$ax_zlib_path" ; then
            ZLIB_CPPFLAGS="-I$ax_zlib_path/include"
            ZLIB_LDFLAGS="-L$ax_zlib_path/lib"
            LD_LIBRARY_PATH="$ax_zlib_path/lib:$LD_LIBRARY_PATH"
          else
            ZLIB_CPPFLAGS=""
            ZLIB_LDFLAGS=""
          fi

          # Required flag for zlib.
          ZLIB_LIBS="-lz"

          # Prepare the environment for compilation.
          CPPFLAGS="$CPPFLAGS $ZLIB_CPPFLAGS"
          LDFLAGS="$LDFLAGS $ZLIB_LDFLAGS"
          LIBS="$LIBS $ZLIB_LIBS"
          export CPPFLAGS
          export LDFLAGS
          export LIBS
          export LD_LIBRARY_PATH

          success=no

          # Compile, link, and run the program.  This checks:
          # - zlib.h is available for including.
          # - zlibVersion() is available for linking.
          # - ZLIB_VERNUM is greater than or equal to the desired version.
          # - ZLIB_VERSION (defined in zlib.h) matches zlibVersion()
          #   (defined in the library).
          AC_LANG_PUSH([C])
          dnl This can be changed to AC_LINK_IFELSE if you are cross-compiling.
          AC_RUN_IFELSE([AC_LANG_PROGRAM([[
          #include <zlib.h>
          #if ZLIB_VERNUM >= 0x$WANT_ZLIB_VERSION
          #else
          # error zlib is too old
          #endif
          ]], [[
          const char* lib_version = zlibVersion();
          const char* hdr_version = ZLIB_VERSION;
          for (;;) {
            if (*lib_version != *hdr_version) {
              /* If this happens, your zlib header doesn't match your zlib */
              /* library.  That is really bad. */
              return 1;
            }
            if (*lib_version == '\0') {
              break;
            }
            lib_version++;
            hdr_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_ZLIB],
         [

          dnl Allow search path to be overridden on the command line.
          AC_ARG_WITH([zlib],
                      AS_HELP_STRING([--with-zlib@<:@=DIR@:>@], [use zlib (default is yes) - it is possible to specify an alternate root directory for zlib]),
                      [
                       if test "x$withval" = "xno"; then
                         want_zlib="no"
                       elif test "x$withval" = "xyes"; then
                         want_zlib="yes"
                         ax_zlib_path=""
                       else
                         want_zlib="yes"
                         ax_zlib_path="$withval"
                       fi
                       ],
                       [want_zlib="yes" ; ax_zlib_path="" ])


          if test "$want_zlib" = "yes"; then
            # Parse out the version.
            zlib_version_req=ifelse([$1], ,1.2.3,$1)
            zlib_version_req_major=`expr $zlib_version_req : '\([[0-9]]*\)'`
            zlib_version_req_minor=`expr $zlib_version_req : '[[0-9]]*\.\([[0-9]]*\)'`
            zlib_version_req_patch=`expr $zlib_version_req : '[[0-9]]*\.[[0-9]]*\.\([[0-9]]*\)'`
            if test -z "$zlib_version_req_patch" ; then
              zlib_version_req_patch="0"
            fi
            WANT_ZLIB_VERSION=`expr $zlib_version_req_major \* 1000 \+  $zlib_version_req_minor \* 100 \+ $zlib_version_req_patch \* 10`

            AC_MSG_CHECKING(for zlib >= $zlib_version_req)

            # Run tests.
            if test -n "$ax_zlib_path"; then
              AX_LIB_ZLIB_DO_CHECK
            else
              for ax_zlib_path in "" /usr /usr/local /opt /opt/zlib "$ZLIB_ROOT" ; do
                AX_LIB_ZLIB_DO_CHECK
                if test "$success" = "yes"; then
                  break;
                fi
              done
            fi

            if test "$success" != "yes" ; then
              AC_MSG_RESULT(no)
              ZLIB_CPPFLAGS=""
              ZLIB_LDFLAGS=""
              ZLIB_LIBS=""
            else
              AC_MSG_RESULT(yes)
              AC_DEFINE(HAVE_ZLIB,,[define if zlib is available])
            fi

            ax_have_zlib="$success"

            AC_SUBST(ZLIB_CPPFLAGS)
            AC_SUBST(ZLIB_LDFLAGS)
            AC_SUBST(ZLIB_LIBS)
          fi

          ])