From 774b63cd41b22f121fec4016fa90933f06289acc Mon Sep 17 00:00:00 2001 From: John Thacker Date: Tue, 14 Apr 2026 08:15:16 -0400 Subject: [PATCH] SMB2: Optimize PATTERN_V1 decompression This is roughly 50x faster on a large decompression. Ping #21191 AI-Assisted: no (cherry picked from commit 0fe4d786017863c9496b7f88098796279dfa59aa) Co-authored-by: John Thacker --- epan/dissectors/packet-smb2.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) Index: wireshark-3.6.24/epan/dissectors/packet-smb2.c =================================================================== --- wireshark-3.6.24.orig/epan/dissectors/packet-smb2.c +++ wireshark-3.6.24/epan/dissectors/packet-smb2.c @@ -10315,8 +10315,24 @@ dissect_smb2_compression_pattern_v1(prot if (out && *ok) { guint8 v = (guint8)pattern; - for (guint i = 0; i < times; i++) + /* Both of these are much faster than adding one byte at a, + * time though the second is somewhat faster in testing due + * to how compilers optimize a known length memset. */ +#if 0 + guint8 *bytes = g_malloc(times); + memset(bytes, v, times); + wmem_array_append(out, bytes, times); + g_free(bytes); +#else + guint8 sixty_four_bytes[64]; + memset(sixty_four_bytes, v, 64); + unsigned i = 0; + for (i = 0; i < times/64; i++) + wmem_array_append(out, sixty_four_bytes, 64); + + for (i *= 64; i < times; i++) wmem_array_append(out, &v, 1); +#endif } return offset;