[gtk-vnc] Make handling of ZRLE encoding more efficient

[Daniel P. Berrange <dberrange src gnome org>]

commit 851f328457507443578078eb78189af4f5e0267f
Author: Artem Rusanov <artem rusanov gmail com>
Date:   Fri Sep 13 12:23:09 2013 +0100

    Make handling of ZRLE encoding more efficient
    
    Avoid memmove() on the uncompressed data buffer when dealing
    with ZRLE encoding. Instead just track what offset we've read
    upto.
    
    Signed-off-by: Daniel P. Berrange <berrange redhat com>

 src/vncconnection.c |   33 ++++++++++++++++++---------------
 1 files changed, 18 insertions(+), 15 deletions(-)
---
diff --git a/src/vncconnection.c b/src/vncconnection.c
index 46f41f7..d476dd4 100644
--- a/src/vncconnection.c
+++ b/src/vncconnection.c
@@ -208,7 +208,8 @@ struct _VncConnectionPrivate
     z_stream *strm;
     z_stream streams[5];
 
-    size_t uncompressed_length;
+    size_t uncompressed_offset;
+    size_t uncompressed_size;
     guint8 uncompressed_buffer[4096];
 
     size_t compressed_length;
@@ -624,19 +625,15 @@ static int vnc_connection_zread(VncConnection *conn, void *buffer, size_t size)
     while (offset < size) {
         /* if data is available in the uncompressed buffer, then
          * copy */
-        if (priv->uncompressed_length) {
-            size_t len = MIN(priv->uncompressed_length,
+        if (priv->uncompressed_size - priv->uncompressed_offset) {
+            size_t len = MIN(priv->uncompressed_size - priv->uncompressed_offset,
                              size - offset);
 
             memcpy(ptr + offset,
-                   priv->uncompressed_buffer,
+                   priv->uncompressed_buffer + priv->uncompressed_offset,
                    len);
 
-            priv->uncompressed_length -= len;
-            if (priv->uncompressed_length)
-                memmove(priv->uncompressed_buffer,
-                        priv->uncompressed_buffer + len,
-                        priv->uncompressed_length);
+            priv->uncompressed_offset += len;
             offset += len;
         } else {
             int err;
@@ -653,7 +650,8 @@ static int vnc_connection_zread(VncConnection *conn, void *buffer, size_t size)
                 return -1;
             }
 
-            priv->uncompressed_length = (guint8 *)priv->strm->next_out - priv->uncompressed_buffer;
+            priv->uncompressed_offset = 0;
+            priv->uncompressed_size = (guint8 *)priv->strm->next_out - priv->uncompressed_buffer;
             priv->compressed_length -= (guint8 *)priv->strm->next_in - priv->compressed_buffer;
             priv->compressed_buffer = priv->strm->next_in;
         }
@@ -2288,7 +2286,8 @@ static void vnc_connection_zrle_update(VncConnection *conn,
     vnc_connection_read(conn, zlib_data, length);
 
     /* setup subsequent calls to vnc_connection_read*() to use the compressed data */
-    priv->uncompressed_length = 0;
+    priv->uncompressed_offset = 0;
+    priv->uncompressed_size = 0;
     priv->compressed_length = length;
     priv->compressed_buffer = zlib_data;
     priv->strm = &priv->streams[0];
@@ -2304,7 +2303,8 @@ static void vnc_connection_zrle_update(VncConnection *conn,
     }
 
     priv->strm = NULL;
-    priv->uncompressed_length = 0;
+    priv->uncompressed_offset = 0;
+    priv->uncompressed_size = 0;
     priv->compressed_length = 0;
     priv->compressed_buffer = NULL;
 
@@ -2568,7 +2568,8 @@ static void vnc_connection_tight_update(VncConnection *conn,
 
             vnc_connection_read(conn, zlib_data, zlib_length);
 
-            priv->uncompressed_length = 0;
+            priv->uncompressed_offset = 0;
+            priv->uncompressed_size = 0;
             priv->compressed_length = zlib_length;
             priv->compressed_buffer = zlib_data;
         }
@@ -2592,7 +2593,8 @@ static void vnc_connection_tight_update(VncConnection *conn,
         }
 
         if (data_size >= 12) {
-            priv->uncompressed_length = 0;
+            priv->uncompressed_offset = 0;
+            priv->uncompressed_size = 0;
             priv->compressed_length = 0;
             priv->compressed_buffer = NULL;
 
@@ -4813,7 +4815,8 @@ static void vnc_connection_close(VncConnection *conn)
 
     priv->read_offset = priv->read_size = 0;
     priv->write_offset = 0;
-    priv->uncompressed_length = 0;
+    priv->uncompressed_offset = 0;
+    priv->uncompressed_size = 0;
     priv->compressed_length = 0;
 
     priv->width = priv->height = 0;