v2writable: introduce idx_stack

This avoids pinning a potentially large chunk of memory from
`git-log --reverse' into RAM (or triggering less predictable
swap behavior).  Instead it uses a contiguous temporary file
with a fixed-size record for every blob we'll need to index.

1 files changed, 56 insertions, 0 deletions

diff --git a/t/idx_stack.t b/t/idx_stack.t
new file mode 100644
index 00000000..35aff37b
--- /dev/null
+++ b/t/idx_stack.t
@@ -0,0 +1,56 @@
+#!perl -w
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use Test::More;
+use_ok 'PublicInbox::IdxStack';
+my $oid_a = '03c21563cf15c241687966b5b2a3f37cdc193316';
+my $oid_b = '963caad026055ab9bcbe3ee9550247f9d8840feb';
+
+my $stk = PublicInbox::IdxStack->new;
+is($stk->read_prepare, $stk, 'nothing');
+is($stk->num_records, 0, 'no records');
+is($stk->pop_rec, undef, 'undef on empty');
+
+$stk = PublicInbox::IdxStack->new;
+$stk->push_rec('m', 1234, 5678, $oid_a);
+is($stk->read_prepare, $stk, 'read_prepare');
+is($stk->num_records, 1, 'num_records');
+is_deeply([$stk->pop_rec], ['m', 1234, 5678, $oid_a], 'pop once');
+is($stk->pop_rec, undef, 'undef on empty');
+
+$stk = PublicInbox::IdxStack->new;
+$stk->push_rec('m', 1234, 5678, $oid_a);
+$stk->push_rec('d', 1234, 5678, $oid_b);
+is($stk->read_prepare, $stk, 'read_prepare');
+is($stk->num_records, 2, 'num_records');
+is_deeply([$stk->pop_rec], ['d', 1234, 5678, $oid_b], 'pop');
+is_deeply([$stk->pop_rec], ['m', 1234, 5678, $oid_a], 'pop-pop');
+is($stk->pop_rec, undef, 'empty');
+
+SKIP: {
+        $stk = undef;
+        my $nr = $ENV{TEST_GIT_LOG} or skip 'TEST_GIT_LOG unset', 3;
+        open my $fh, '-|', qw(git log --pretty=tformat:%at.%ct.%H), "-$nr" or
+                die "git log: $!";
+        my @expect;
+        while (<$fh>) {
+                chomp;
+                my ($at, $ct, $H) = split(/\./);
+                $stk //= PublicInbox::IdxStack->new($H);
+                # not bothering to parse blobs here, just using commit OID
+                # as a blob OID since they're the same size + format
+                $stk->push_rec('m', $at + 0, $ct + 0, $H);
+                push(@expect, [ 'm', $at, $ct, $H ]);
+        }
+        $stk or skip('nothing from git log', 3);
+        is($stk->read_prepare, $stk, 'read_prepare');
+        is($stk->num_records, scalar(@expect), 'num_records matches expected');
+        my @result;
+        while (my @tmp = $stk->pop_rec) {
+                unshift @result, \@tmp;
+        }
+        is_deeply(\@result, \@expect, 'results match expected');
+}
+
+done_testing;