preliminary imap server implementation

It shares a bit of code with NNTP.  It's copy+pasted for now
since this provides new ground to experiment with APIs for
dealing with slow storage and many inboxes.

1 files changed, 119 insertions, 0 deletions

diff --git a/lib/PublicInbox/IMAPdeflate.pm b/lib/PublicInbox/IMAPdeflate.pm
new file mode 100644
index 00000000..9366db7a
--- /dev/null
+++ b/lib/PublicInbox/IMAPdeflate.pm
@@ -0,0 +1,119 @@
+# Copyright (C) 2020 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+# TODO: reduce duplication from PublicInbox::NNTPdeflate
+
+# RFC 4978
+package PublicInbox::IMAPdeflate;
+use strict;
+use warnings;
+use 5.010_001;
+use base qw(PublicInbox::IMAP);
+use Compress::Raw::Zlib;
+use Hash::Util qw(unlock_hash); # dependency of fields for perl 5.10+, anyways
+
+my %IN_OPT = (
+        -Bufsize => 1024,
+        -WindowBits => -15, # RFC 1951
+        -AppendOutput => 1,
+);
+
+# global deflate context and buffer
+my $zbuf = \(my $buf = '');
+my $zout;
+{
+        my $err;
+        ($zout, $err) = Compress::Raw::Zlib::Deflate->new(
+                # nnrpd (INN) and Compress::Raw::Zlib favor MemLevel=9,
+                # the zlib C library and git use MemLevel=8 as the default
+                # -MemLevel => 9,
+                -Bufsize => 65536, # same as nnrpd
+                -WindowBits => -15, # RFC 1951
+                -AppendOutput => 1,
+        );
+        $err == Z_OK or die "Failed to initialize zlib deflate stream: $err";
+}
+
+sub enable {
+        my ($class, $self, $tag) = @_;
+        my ($in, $err) = Compress::Raw::Zlib::Inflate->new(%IN_OPT);
+        if ($err != Z_OK) {
+                $self->err("Inflate->new failed: $err");
+                $self->write(\"$tag BAD failed to activate compression\r\n");
+                return;
+        }
+        unlock_hash(%$self);
+        $self->write(\"$tag OK DEFLATE active\r\n");
+        bless $self, $class;
+        $self->{zin} = $in;
+}
+
+# overrides PublicInbox::NNTP::compressed
+sub compressed { 1 }
+
+# $_[1] may be a reference or not
+sub do_read ($$$$) {
+        my ($self, $rbuf, $len, $off) = @_;
+
+        my $zin = $self->{zin} or return; # closed
+        my $doff;
+        my $dbuf = delete($self->{dbuf}) // '';
+        $doff = length($dbuf);
+        my $r = PublicInbox::DS::do_read($self, \$dbuf, $len, $doff) or return;
+
+        # assert(length($$rbuf) == $off) as far as NNTP.pm is concerned
+        # -ConsumeInput is true, so $dbuf is automatically emptied
+        my $err = $zin->inflate($dbuf, $rbuf);
+        if ($err == Z_OK) {
+                $self->{dbuf} = $dbuf if $dbuf ne '';
+                $r = length($$rbuf) and return $r;
+                # nothing ready, yet, get more, later
+                $self->requeue;
+        } else {
+                delete $self->{zin};
+                $self->close;
+        }
+        0;
+}
+
+# override PublicInbox::DS::msg_more
+sub msg_more ($$) {
+        my $self = $_[0];
+
+        # $_[1] may be a reference or not for ->deflate
+        my $err = $zout->deflate($_[1], $zbuf);
+        $err == Z_OK or die "->deflate failed $err";
+        1;
+}
+
+sub zflush ($) {
+        my ($self) = @_;
+
+        my $deflated = $zbuf;
+        $zbuf = \(my $next = '');
+
+        my $err = $zout->flush($deflated, Z_FULL_FLUSH);
+        $err == Z_OK or die "->flush failed $err";
+
+        # We can still let the lower socket layer do buffering:
+        PublicInbox::DS::msg_more($self, $$deflated);
+}
+
+# compatible with PublicInbox::DS::write, so $_[1] may be a reference or not
+sub write ($$) {
+        my $self = $_[0];
+        return PublicInbox::DS::write($self, $_[1]) if ref($_[1]) eq 'CODE';
+
+        my $deflated = $zbuf;
+        $zbuf = \(my $next = '');
+
+        # $_[1] may be a reference or not for ->deflate
+        my $err = $zout->deflate($_[1], $deflated);
+        $err == Z_OK or die "->deflate failed $err";
+        $err = $zout->flush($deflated, Z_FULL_FLUSH);
+        $err == Z_OK or die "->flush failed $err";
+
+        # We can still let the socket layer do buffering:
+        PublicInbox::DS::write($self, $deflated);
+}
+
+1;