Subject: [PATCH v2 2/3] pkt-line: memorize sideband fragment in reader

From: Jiang Xin <[email-masked]>
Date: Mon, 25 Sep 2023 23:41:43 +0800

From: Jiang Xin <[email-masked]>

When we turn on the "use_sideband" field of the packet_reader,
"packet_reader_read()" will call the function "demultiplex_sideband()"
to parse and consume sideband messages. Sideband fragment which does not
end with "\r" or "\n" will be saved in the sixth parameter "scratch"
and it can be reused and be concatenated when parsing another sideband
message.

In "packet_reader_read()" function, the local variable "scratch" can
only be reused by subsequent sideband messages. But if there is a
payload message between two sideband fragments, the first fragment
which is saved in the local variable "scratch" will be lost.

To solve this problem, we can add a new field "scratch" in
packet_reader to memorize the sideband fragment across different calls
of "packet_reader_read()".

Signed-off-by: Jiang Xin <[email-masked]>
---
 pkt-line.c             | 5 ++---
 pkt-line.h             | 3 +++
 t/t0070-fundamental.sh | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/pkt-line.c b/pkt-line.c
index af83a19f4d..5943777a17 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -592,12 +592,11 @@ void packet_reader_init(struct packet_reader *reader, int fd,
 	reader->options = options;
 	reader->me = "git";
 	reader->hash_algo = &hash_algos[GIT_HASH_SHA1];
+	strbuf_init(&reader->scratch, 0);
 }
 
 enum packet_read_status packet_reader_read(struct packet_reader *reader)
 {
-	struct strbuf scratch = STRBUF_INIT;
-
 	if (reader->line_peeked) {
 		reader->line_peeked = 0;
 		return reader->status;
@@ -620,7 +619,7 @@ enum packet_read_status packet_reader_read(struct packet_reader *reader)
 			break;
 		if (demultiplex_sideband(reader->me, reader->status,
 					 reader->buffer, reader->pktlen, 1,
-					 &scratch, &sideband_type))
+					 &reader->scratch, &sideband_type))
 			break;
 	}
 
diff --git a/pkt-line.h b/pkt-line.h
index 954eec8719..be1010d34e 100644
--- a/pkt-line.h
+++ b/pkt-line.h
@@ -194,6 +194,9 @@ struct packet_reader {
 
 	/* hash algorithm in use */
 	const struct git_hash_algo *hash_algo;
+
+	/* hold temporary sideband message */
+	struct strbuf scratch;
 };
 
 /*
diff --git a/t/t0070-fundamental.sh b/t/t0070-fundamental.sh
index 1053913d2d..a927c665d6 100755
--- a/t/t0070-fundamental.sh
+++ b/t/t0070-fundamental.sh
@@ -81,7 +81,7 @@ test_expect_success 'unpack-sideband: --chomp-newline (default)' '
 	test_cmp expect-err err
 '
 
-test_expect_failure 'unpack-sideband with demultiplex_sideband(), no chomp newline' '
+test_expect_success 'unpack-sideband with demultiplex_sideband(), no chomp newline' '
 	test_when_finished "rm -f expect-out expect-err" &&
 	test-tool pkt-line send-split-sideband >split-sideband &&
 	test-tool pkt-line unpack-sideband \
-- 
2.40.1.50.gf560bcc116.dirty