From 7eea19633c574c7002cc41d8a6f7ccbb0e941dda Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Mangano?= <fmang@mg0.fr>
Date: Fri, 27 Jan 2023 15:19:59 +0900
Subject: [PATCH] Support multiple-page OpusTags packets

---
 src/ogg.cc   | 40 +++++++++++++++++++++-------------------
 t/opustags.t | 12 +++++++++++-
 2 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/src/ogg.cc b/src/ogg.cc
index cc149ee..074317e 100644
--- a/src/ogg.cc
+++ b/src/ogg.cc
@@ -57,19 +57,28 @@ void ot::ogg_reader::process_header_packet(const std::function<void(ogg_packet&)
 {
 	if (ogg_page_continued(&page))
 		throw status {ot::st::error, "Unexpected continued header page."};
-	ogg_logical_stream stream(ogg_page_serialno(&page));
-	stream.pageno = ogg_page_pageno(&page);
-	if (ogg_stream_pagein(&stream, &page) != 0)
-		throw status {st::libogg_error, "ogg_stream_pagein failed."};
 
 	ogg_packet packet;
-	int rc = ogg_stream_packetout(&stream, &packet);
-	if (ogg_stream_check(&stream) != 0 || rc == -1)
-		throw status {ot::st::libogg_error, "ogg_stream_packetout failed."};
-	else if (rc == 0)
-		throw status {ot::st::error,
-		              "Reading header packets spanning multiple pages are not yet supported. "
-		              "Please file an issue to make your wish known."};
+	ogg_logical_stream stream(ogg_page_serialno(&page));
+	stream.pageno = ogg_page_pageno(&page);
+
+	for (;;) {
+		if (ogg_stream_pagein(&stream, &page) != 0)
+			throw status {st::libogg_error, "ogg_stream_pagein failed."};
+
+		int rc = ogg_stream_packetout(&stream, &packet);
+		if (ogg_stream_check(&stream) != 0 || rc == -1) {
+			throw status {ot::st::libogg_error, "ogg_stream_packetout failed."};
+		} else if (rc == 0) {
+			// Not enough data: read the next page.
+			if (!next_page())
+				throw status {ot::st::error, "Unterminated header packet."};
+			continue;
+		} else {
+			// The packet was successfully read.
+			break;
+		}
+	}
 
 	f(packet);
 
@@ -109,15 +118,8 @@ void ot::ogg_writer::write_header_packet(int serialno, int pageno, ogg_packet& p
 		throw status {ot::st::libogg_error, "ogg_stream_packetin failed"};
 
 	ogg_page page;
-	if (ogg_stream_flush(&stream, &page) != 0)
+	while (ogg_stream_flush(&stream, &page) != 0)
 		write_page(page);
-	else
-		throw status {ot::st::libogg_error, "ogg_stream_flush failed"};
-
-	if (ogg_stream_flush(&stream, &page) != 0)
-		throw status {ot::st::error,
-		              "Writing header packets spanning multiple pages are not yet supported. "
-		              "Please file an issue to make your wish known."};
 
 	if (ogg_stream_check(&stream) != 0)
 		throw status {st::libogg_error, "ogg_stream_check failed"};
diff --git a/t/opustags.t b/t/opustags.t
index 6a15f53..c3e15f7 100755
--- a/t/opustags.t
+++ b/t/opustags.t
@@ -4,7 +4,7 @@ use strict;
 use warnings;
 use utf8;
 
-use Test::More tests => 50;
+use Test::More tests => 54;
 
 use Digest::MD5;
 use File::Basename;
@@ -311,3 +311,13 @@ U=\xFE
 END_OUT
 
 unlink('out.opus');
+
+####################################################################################################
+# Multiple-page tags
+
+my $big_tags = "DATA=x\n" x 15000; # > 90K, which is over the max page size of 64KiB.
+is_deeply(opustags(qw(-S gobble.opus -o out.opus), {in => $big_tags}), ['', '', 0], 'write multi-page header');
+is_deeply(opustags('out.opus'), [$big_tags, '', 0], 'read multi-page header');
+is_deeply(opustags(qw(out.opus -i -D -a), 'encoder=Lavc58.18.100 libopus'), ['', '', 0], 'shrink the header');
+is(md5('out.opus'), '111a483596ac32352fbce4d14d16abd2', 'the result is identical to the original file');
+unlink('out.opus');