source: vendor/bash/3.1/examples/functions/autoload.v3

#From: Mark Kennedy <mtk@ny.ubs.com>
#Message-ID: <35E2B899.63A02DF5@ny.ubs.com>
#Date: Tue, 25 Aug 1998 09:14:01 -0400
#To: chet@nike.ins.cwru.edu
#Subject: a newer version of the ksh-style 'autoload'

#enclosed you'll find 'autoload.v3',  a version of the autoloader
#that emulates the ksh semantics of delaying the resolution (and loading) of the function
#until its first use.  i took the liberty of simplifying the code a bit although it still uses the
#same functional breakdown.  i recently went through the exercise of converting
#my ksh-based environment to bash (a very, very pleasant experience)
#and this popped out.

# the psuedo-ksh autoloader.

# The first cut of this was by Bill Trost, trost@reed.bitnet.
# The second cut came from Chet Ramey, chet@ins.CWRU.Edu
# The third cut came from Mark Kennedy, mtk@ny.ubs.com.  1998/08/25

unset _AUTOLOADS

_aload()
{
    local func
    for func; do
        eval $func '()
                {
                    local f=$(_autoload_resolve '$func')
                    if [[ $f ]]; then
                        . $f
                        '$func' "$@"
                        return $?
                    else
                        return 1
                    fi
                }'
        _autoload_addlist $func
    done
}

_autoload_addlist()
{
        local func

        for func in ${_AUTOLOADS[@]}; do
            [[ $func = "$1" ]] && return
        done

        _AUTOLOADS[${#_AUTOLOADS[@]}]=$1
}

_autoload_dump()
{
    local func

    for func in ${_AUTOLOADS[@]}; do
        [[ $1 ]] && echo -n "autoload "
        echo $func
    done
}

_autoload_remove_one()
{
    local func
    local -a NEW_AUTOLOADS

    for func in ${_AUTOLOADS[@]}; do
        [[ $func != "$1" ]] && NEW_AUTOLOADS[${#NEW_AUTOLOADS[@]}]=$func
    done

    _AUTOLOADS=( ${NEW_AUTOLOADS[@]} )
}

_autoload_remove()
{
    local victim func

    for victim; do
        for func in ${_AUTOLOADS[@]}; do
            [[ $victim = "$func" ]] && unset -f $func && continue 2
        done
        echo "autoload: $func: not an autoloaded function" >&2
    done

    for func; do
            _autoload_remove_one $func
    done
}

_autoload_resolve()
{
    if [[ ! "$FPATH" ]]; then
            echo "autoload: FPATH not set or null" >&2
            return
    fi

    local p

    for p in $( (IFS=':'; set -- ${FPATH}; echo "$@") ); do
        p=${p:-.}
        if [ -f $p/$1 ]; then echo $p/$1; return; fi
    done

    echo "autoload: $1: function source file not found" >&2
}

autoload()
{
    if (( $# == 0 )) ; then _autoload_dump; return; fi

    local opt OPTIND

    while getopts pu opt
    do
        case $opt in
            p) _autoload_dump printable; return;;
            u) shift $((OPTIND-1)); _autoload_remove "$@"; return;; 
            *) echo "autoload: usage: autoload [-pu] [function ...]" >&2; return;;
        esac
    done

    shift $(($OPTIND-1))

    _aload "$@"
}