Macro: etr_short_sleep

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# etr_short_sleep

## Synopsis

`ETR_SHORT_SLEEP`

## Version

1.1 (2001/07/26) Miscellaneous @ ac-archive-0.5.32

## Author

Warren Young <warren@etr-usa.com>

## Description

This macro searches for a "sleep" function that has 1/1000 of a second accuracy. On some systems, this is known as nap() and on others usleep() / 1000. There are probably other functions like this defined in other system libraries, but we don't know how to search for them yet. Contributions joyously accepted. :)

## M4 Source Code

    AC_DEFUN([ETR_SHORT_SLEEP],
    [
            AC_MSG_CHECKING([for nap() in libc])
            AC_TRY_LINK([ extern "C" long nap(long ms); ], [ nap(42); ],
                    [
                            etr_ss_found=yes
                            etr_ss_factor=1
                            AC_DEFINE(HAVE_NAP,1,
                                    [Define to use the nap() system call for short sleeps])
                            AC_MSG_RESULT(yes)
                    ],
                    [
                            AC_MSG_RESULT(no)
                            etr_ss_found=no
                    ])

            if test x"$etr_ss_found" = "xno"
            then
                    AC_MSG_CHECKING([for usleep()])
                    AC_TRY_LINK([ #include <unistd.h> ], [ usleep(42); ],
                            [
                                    etr_ss_found=yes
                                    etr_ss_factor=1000
                                    AC_DEFINE(HAVE_USLEEP,1,
                                            [Define to use the usleep() system call for short sleeps])
                                    AC_MSG_RESULT(yes)
                            ],
                            [
                                    AC_MSG_RESULT(no)
                                    etr_ss_found=no
                            ])
            fi

            if test x"$etr_ss_found" = "xno"
            then
                    save_LIBS=$LIBS
                    LIBS="$LIBS -lx"
                    AC_MSG_CHECKING([for nap() in libx])
                    AC_TRY_LINK([ extern "C" long nap(long ms); ], [ nap(42); ],
                            [
                                    etr_ss_found=yes
                                    etr_ss_factor=1
                                    AC_DEFINE(HAVE_NAP,1,
                                            [Define to use the nap() system call for short sleeps])
                                    AC_MSG_RESULT(yes)
                            ],
                            [
                                    AC_MSG_RESULT(no)
                                    etr_ss_found=no
                            ])

                    LIBS=$save_LIBS
                    ETR_SS_LIB=-lx
                    AC_SUBST(ETR_SS_LIB)
            fi

            if test x"$etr_ss_found" = "xyes"
            then
                    AC_DEFINE_UNQUOTED(SHORT_SLEEP_FACTOR, $etr_ss_factor,
                            [Multiply milliseconds by this to get the argument for the short sleep system call])
            else
                    AC_MSG_ERROR([Could not find a "short sleep" system call.])
            fi
    ])dnl ETR_SHORT_SLEEP