File vnc-prioritize-ZRLE-compression-over-ZLI.patch of Package qemu.21548

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File vnc-prioritize-ZRLE-compression-over-ZLI.patch of Package qemu.21548

From: Cameron Esfahani <dirty@apple.com>
Date: Mon, 20 Jan 2020 21:00:52 -0800
Subject: vnc: prioritize ZRLE compression over ZLIB

Git-commit: 557ba0e57200014bd4f453f6516f02b61bdfc782

In my investigation, ZRLE always compresses better than ZLIB so
prioritize ZRLE over ZLIB, even if the client hints that ZLIB is
preferred.

zlib buffer is always reset in zrle_compress_data(), so using offset to
calculate next_out and avail_out is useless.

Signed-off-by: Cameron Esfahani <dirty@apple.com>
Message-Id: <b5d129895d08a90d0a2a6183b95875bacfa998b8.1579582674.git.dirty@apple.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Bruce Rogers <brogers@suse.com>
---
 ui/vnc-enc-zrle.c |  4 ++--
 ui/vnc.c          | 11 +++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/ui/vnc-enc-zrle.c b/ui/vnc-enc-zrle.c
index 17fd28a2e2b078bd135496e75c6b..b4f71e32cfe8ca3dd645103f999d 100644
--- a/ui/vnc-enc-zrle.c
+++ b/ui/vnc-enc-zrle.c
@@ -98,8 +98,8 @@ static int zrle_compress_data(VncState *vs, int level)
     /* set pointers */
     zstream->next_in = vs->zrle->zrle.buffer;
     zstream->avail_in = vs->zrle->zrle.offset;
-    zstream->next_out = vs->zrle->zlib.buffer + vs->zrle->zlib.offset;
-    zstream->avail_out = vs->zrle->zlib.capacity - vs->zrle->zlib.offset;
+    zstream->next_out = vs->zrle->zlib.buffer;
+    zstream->avail_out = vs->zrle->zlib.capacity;
     zstream->data_type = Z_BINARY;
 
     /* start encoding */
diff --git a/ui/vnc.c b/ui/vnc.c
index f94b3a257ee3add364a0b0bd5101..70bd8bf05d163e2ef0911c3b19fd 100644
--- a/ui/vnc.c
+++ b/ui/vnc.c
@@ -2077,8 +2077,15 @@ static void set_encodings(VncState *vs, int32_t *encodings, size_t n_encodings)
             break;
 #endif
         case VNC_ENCODING_ZLIB:
-            vs->features |= VNC_FEATURE_ZLIB_MASK;
-            vs->vnc_encoding = enc;
+            /*
+             * VNC_ENCODING_ZRLE compresses better than VNC_ENCODING_ZLIB.
+             * So prioritize ZRLE, even if the client hints that it prefers
+             * ZLIB.
+             */
+            if ((vs->features & VNC_FEATURE_ZRLE_MASK) == 0) {
+                vs->features |= VNC_FEATURE_ZLIB_MASK;
+                vs->vnc_encoding = enc;
+            }
             break;
         case VNC_ENCODING_ZRLE:
             vs->features |= VNC_FEATURE_ZRLE_MASK;

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File vnc-prioritize-ZRLE-compression-over-ZLI.patch of Package qemu.21548

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