[gentoo-dev] Re: New eclass osgi.eclass

[Steve Long]

Alistair Bush wrote:
> Im sure Elvanor can't wait for you constructive feedback on his eclass
> and depending on your feedback the eclass will enter the tree this
> weekend.
>
A couple of very minor performance points, which I think are more
significant in eclasses. Firstly the basename thing Donnie pointed out
before:
> >       local feedfile=$(basename "${src}")
> You could do this in pure bash, although it doesn't really matter:
> local feedfile=${src##*/}

[[ ${#} -lt 4 ]] && die "At least four arguments needed"
Arithmetic context is quicker for this:
(($#<4)) && die "At least four arguments needed"
although in this case, _java-pkg_osgijar(), it looks it requires exactly 4:
(($#==4)) || die 'Four arguments needed'

You have a couple of functions that take, say, 4 or 5 arguments. It would be
more robust to use a case, eg:
case $# in
5)..;;
4)..;;
*) die "Incorrect use of $FUNCNAME";;
esac
..than if (($#>4)); then ..; else .. ;fi

 _java-pkg_osgi-plugin ${4} # this should be quoted (_java-pkg_osgijar)

With regard to:
 debug-print-function ${FUNCNAME} $*
if you want debug-print-function to get the arguments correctly, use "$@"
not $* (cf 'Special Parameters' in man bash for a proper explanation: this
applies to all arrays. http://wooledge.org/mywiki/BashFAQ/073 shows how to
manipulate all members of an array, eg to add a prefix.)

This use of counter in _java-pkg_osgijar-fromfile is odd:
while [[ -n "${1}" ]]; do
# while [[ $1 ]] or while (($#)) also work
   if [[ "${1}" == "--noversion" ]]; then
      noversion=1
   else
      arguments[${counter}]="${1}"
      ((++counter))
   fi
   shift 1 # just shift?
done

((${#arguments[@]} < 3)) && die "At least three arguments (not
counting --noversion) are needed for java-pkg_osgijar-fromfile()"

You can either just add to the array with: arguments+=("$1")
or add using the counter: arguments[counter++]="$1"
and then check: ((counter < 3)) && die ..

Arithmetic context[1] applies in array indexes, so you don't need to use a $
for variables and you can post/pre-incr etc there.
Yuu can also use it for C-style flags, with 0 as false and non-zero true:
if [[ "${noversion}" == 1 ]];
can be
if ((noversion));

This is handy since unset variables evaluate as zero, which is false inside
((..)), so a simple flag=1 is all that's needed, ie you don't have to set a
default, although ofc it's more robust to do so, especially for functions.
declare -i flag=0 # makes a local var which can only have integer values
assigned (setting it to string typically evaluates to zero; arithmetic
context is used for all assignments, so a string which happens to be a
variable with an integer will return that value.)

[1] http://wooledge.org/mywiki/ArithmeticExpression


-- 
gentoo-dev@g.o mailing list