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Supplier.pm6
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Supplier.pm6
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# A Supplier is a convenient way to create a live Supply. The publisher can
# be used to emit/done/quit. The Supply objects obtained from it will tap into
# the same live Supply.
my class Supplier {
my class TapList does Tappable {
my class TapListEntry {
has &.emit;
has &.done;
has &.quit;
}
# Lock serializes updates to tappers.
has Lock $!lock = Lock.new;
# An immutable list of tappers. Always replaced on change, never
# mutated in-place ==> thread safe together with lock (and only
# need lock on modification).
has Mu $!tappers;
method tap(&emit, &done, &quit, &tap) {
my $tle := TapListEntry.new(:&emit, :&done, :&quit);
# Since we run `tap` before adding, there's a small chance of
# a tap removal attempt happening for the add attempt. We use
# these two flags to handle that case. This is safe since we
# only ever access them under lock.
my $added := False;
my $removed := False;
my $t = Tap.new({
$!lock.protect({
if $added {
my Mu $update := nqp::list();
for nqp::hllize($!tappers) -> \entry {
nqp::push($update, entry) unless entry =:= $tle;
}
$!tappers := $update;
}
$removed := True;
});
});
tap($t);
$!lock.protect({
unless $removed {
my Mu $update := nqp::isconcrete($!tappers)
?? nqp::clone($!tappers)
!! nqp::list();
nqp::push($update, $tle);
$!tappers := $update;
}
$added := True;
});
$t
}
method emit(Mu \value --> Nil) {
nqp::if(
nqp::isconcrete(my $snapshot := $!tappers)
&& (my int $n = nqp::elems($snapshot)),
nqp::if( # at least one tap
nqp::isgt_i($n,1),
nqp::stmts( # multiple taps
(my int $i = -1),
nqp::while(
nqp::islt_i(($i = nqp::add_i($i,1)),$n),
nqp::atpos($snapshot,$i).emit()(value)
)
),
nqp::atpos($snapshot,0).emit()(value) # only one tap
)
)
}
method done(--> Nil) {
my $snapshot := $!tappers;
if nqp::isconcrete($snapshot) {
my int $n = nqp::elems($snapshot);
loop (my int $i = 0; $i < $n; $i = $i + 1) {
nqp::atpos($snapshot, $i).done()();
}
}
}
method quit($ex --> Nil) {
my $snapshot := $!tappers;
if nqp::isconcrete($snapshot) {
my int $n = nqp::elems($snapshot);
loop (my int $i = 0; $i < $n; $i = $i + 1) {
nqp::atpos($snapshot, $i).quit()($ex);
}
}
}
method live(--> True) { }
method serial(--> False) { }
method sane(--> False) { }
}
has $!taplist;
method new() {
self.bless(taplist => TapList.new)
}
submethod BUILD(:$!taplist! --> Nil) { }
method emit(Supplier:D: Mu \value --> Nil) {
$!taplist.emit(value);
}
method done(Supplier:D: --> Nil) {
$!taplist.done();
}
proto method quit($) {*}
multi method quit(Supplier:D: Exception $ex) {
$!taplist.quit($ex);
}
multi method quit(Supplier:D: Str() $message) {
$!taplist.quit(X::AdHoc.new(payload => $message));
}
method Supply(Supplier:D:) {
Supply.new($!taplist).sanitize
}
method unsanitized-supply(Supplier:D:) {
Supply.new($!taplist)
}
}
# A preserving supplier holds on to emitted values and state when nobody is
# tapping. As soon as there a tap is made, any preserved events will be
# immediately sent to that tapper.
my class Supplier::Preserving is Supplier {
my class PreservingTapList does Tappable {
my class TapListEntry {
has &.emit;
has &.done;
has &.quit;
}
# Lock serializes updates to tappers.
has Lock $!lock = Lock.new;
# An immutable list of tappers. Always replaced on change, never
# mutated in-place ==> thread safe together with lock (and only
# need lock on modification).
has Mu $!tappers;
# Events to reply, whether the replay was done, and a lock to protect
# updates to these.
has @!replay;
has int $!replay-done;
has $!replay-lock = Lock.new;
method tap(&emit, &done, &quit, &tap) {
my $tle := TapListEntry.new(:&emit, :&done, :&quit);
my int $replay = 0;
# Since we run `tap` before adding, there's a small chance of
# a tap removal attempt happening for the add attempt. We use
# these two flags to handle that case. This is safe since we
# only ever access them under lock.
my $added := False;
my $removed := False;
my $t = Tap.new({
$!lock.protect({
if $added {
my Mu $update := nqp::list();
for nqp::hllize($!tappers) -> \entry {
nqp::push($update, entry) unless entry =:= $tle;
}
$!replay-done = 0 if nqp::elems($update) == 0;
$!tappers := $update;
}
$removed := True;
});
});
tap($t);
$!lock.protect({
unless $removed {
my Mu $update := nqp::isconcrete($!tappers)
?? nqp::clone($!tappers)
!! nqp::list();
nqp::push($update, $tle);
$replay = 1 if nqp::elems($update) == 1;
self!replay($tle) if $replay;
$!tappers := $update;
}
$added := True;
});
$t
}
method emit(\value --> Nil) {
loop {
my int $sent = 0;
my $snapshot := $!tappers;
if nqp::isconcrete($snapshot) {
$sent = nqp::elems($snapshot);
loop (my int $i = 0; $i < $sent; $i = $i + 1) {
nqp::atpos($snapshot, $i).emit()(value);
}
}
return if $sent;
return if self!add-replay({ $_.emit()(value) });
}
}
method done(--> Nil) {
loop {
my int $sent = 0;
my $snapshot := $!tappers;
if nqp::isconcrete($snapshot) {
$sent = nqp::elems($snapshot);
loop (my int $i = 0; $i < $sent; $i = $i + 1) {
nqp::atpos($snapshot, $i).done()();
}
}
return if $sent;
return if self!add-replay({ $_.done()() });
}
}
method quit($ex --> Nil) {
loop {
my int $sent = 0;
my $snapshot := $!tappers;
if nqp::isconcrete($snapshot) {
$sent = nqp::elems($snapshot);
loop (my int $i = 0; $i < $sent; $i = $i + 1) {
nqp::atpos($snapshot, $i).quit()($ex);
}
}
return if $sent;
return if self!add-replay({ $_.quit()($ex) });
}
}
method !add-replay(&replay --> Bool) {
$!replay-lock.protect: {
if $!replay-done {
False
}
else {
@!replay.push(&replay);
True
}
}
}
method !replay($tle) {
$!replay-lock.protect: {
while @!replay.shift -> $rep {
$rep($tle);
}
$!replay-done = 1;
}
}
method live(--> True) { }
method serial(--> False) { }
method sane(--> False) { }
}
method new() {
self.bless(taplist => PreservingTapList.new)
}
}
# vim: expandtab shiftwidth=4