+ cat_async_step($self, $inflight); # take one step
+}
+
+sub cat_async_step ($$) {
+ my ($self, $inflight) = @_;
+ die 'BUG: inflight empty or odd' if scalar(@$inflight) < 3;
+ my ($req, $cb, $arg) = splice(@$inflight, 0, 3);
+ my $rbuf = delete($self->{cat_rbuf}) // \(my $new = '');
+ my ($bref, $oid, $type, $size);
+ my $head = my_readline($self->{in}, $rbuf);
+ # ->fail may be called via Gcf2Client.pm
+ if ($head =~ /^([0-9a-f]{40,}) (\S+) ([0-9]+)$/) {
+ ($oid, $type, $size) = ($1, $2, $3 + 0);
+ $bref = my_read($self->{in}, $rbuf, $size + 1) or
+ $self->fail(defined($bref) ? 'read EOF' : "read: $!");
+ chop($$bref) eq "\n" or $self->fail('LF missing after blob');
+ } elsif ($head =~ s/ missing\n//s) {
+ $oid = $head;
+ # ref($req) indicates it's already been retried
+ # -gcf2 retries internally, so it never hits this path:
+ if (!ref($req) && !$in_cleanup && $self->alternates_changed) {
+ return cat_async_retry($self, $inflight,
+ $req, $cb, $arg);
+ }
+ $type = 'missing';
+ $oid = ref($req) ? $$req : $req if $oid eq '';
+ } else {
+ my $err = $! ? " ($!)" : '';
+ $self->fail("bad result from async cat-file: $head$err");
+ }
+ $self->{cat_rbuf} = $rbuf if $$rbuf ne '';
+ eval { $cb->($bref, $oid, $type, $size, $arg) };
+ warn "E: $oid: $@\n" if $@;
+}
+
+sub cat_async_wait ($) {
+ my ($self) = @_;
+ my $inflight = $self->{inflight} or return;
+ while (scalar(@$inflight)) {
+ cat_async_step($self, $inflight);
+ }
+}
+
+sub batch_prepare ($) {
+ _bidi_pipe($_[0], qw(--batch in out pid));
+}
+
+sub _cat_file_cb {
+ my ($bref, undef, undef, $size, $result) = @_;
+ @$result = ($bref, $size);
+}
+
+sub cat_file {
+ my ($self, $oid, $sizeref) = @_;
+ my $result = [];
+ cat_async($self, $oid, \&_cat_file_cb, $result);
+ cat_async_wait($self);
+ $$sizeref = $result->[1] if $sizeref;
+ $result->[0];
+}
+
+sub check_async_step ($$) {
+ my ($self, $inflight_c) = @_;
+ die 'BUG: inflight empty or odd' if scalar(@$inflight_c) < 3;
+ my ($req, $cb, $arg) = splice(@$inflight_c, 0, 3);
+ my $rbuf = delete($self->{chk_rbuf}) // \(my $new = '');
+ chomp(my $line = my_readline($self->{in_c}, $rbuf));
+ my ($hex, $type, $size) = split(/ /, $line);
+
+ # Future versions of git.git may have type=ambiguous, but for now,
+ # we must handle 'dangling' below (and maybe some other oddball
+ # stuff):
+ # https://public-inbox.org/git/20190118033845.s2vlrb3wd3m2jfzu@dcvr/T/
+ if ($hex eq 'dangling' || $hex eq 'notdir' || $hex eq 'loop') {
+ my $ret = my_read($self->{in_c}, $rbuf, $type + 1);
+ $self->fail(defined($ret) ? 'read EOF' : "read: $!") if !$ret;
+ }
+ $self->{chk_rbuf} = $rbuf if $$rbuf ne '';
+ eval { $cb->($hex, $type, $size, $arg, $self) };
+ warn "E: check($req) $@\n" if $@;
+}
+
+sub check_async_wait ($) {
+ my ($self) = @_;
+ my $inflight_c = $self->{inflight_c} or return;
+ while (scalar(@$inflight_c)) {
+ check_async_step($self, $inflight_c);
+ }
+}
+
+sub check_async_begin ($) {
+ my ($self) = @_;
+ cleanup($self) if alternates_changed($self);
+ _bidi_pipe($self, qw(--batch-check in_c out_c pid_c err_c));
+ die 'BUG: already in async check' if $self->{inflight_c};
+ $self->{inflight_c} = [];
+}
+
+sub check_async ($$$$) {
+ my ($self, $oid, $cb, $arg) = @_;
+ my $inflight_c = $self->{inflight_c} // check_async_begin($self);
+ while (scalar(@$inflight_c) >= MAX_INFLIGHT) {
+ check_async_step($self, $inflight_c);
+ }
+ print { $self->{out_c} } $oid, "\n" or $self->fail("write error: $!");
+ push(@$inflight_c, $oid, $cb, $arg);
+}
+
+sub _check_cb { # check_async callback
+ my ($hex, $type, $size, $result) = @_;
+ @$result = ($hex, $type, $size);