Fix bug #6237.

 w32.c (sys_write): Break writes into chunks smaller than 32MB.

2 files changed, 33 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 489505f3cf3..540a85a6b1d 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2010-05-22  Eli Zaretskii  <eliz@gnu.org>
+
+        * w32.c (sys_write): Break writes into chunks smaller than 32MB.
+        (Bug#6237)
+
 2010-05-22  Chong Yidong  <cyd@stupidchicken.com>
 
         * image.c (Fimage_flush): Rename from image-refresh.
diff --git a/src/w32.c b/src/w32.c
index 0f2d8b54e6b..0560ce4a6b8 100644
--- a/src/w32.c
+++ b/src/w32.c
@@ -5700,7 +5700,34 @@ sys_write (int fd, const void * buffer, unsigned int count)
     }
   else
 #endif
-    nchars = _write (fd, buffer, count);
+    {
+      /* Some networked filesystems don't like too large writes, so
+         break them into smaller chunks.  See the Comments section of
+         the MSDN documentation of WriteFile for details behind the
+         choice of the value of CHUNK below.  See also the thread
+         http://thread.gmane.org/gmane.comp.version-control.git/145294
+         in the git mailing list.  */
+      const unsigned char *p = buffer;
+      const unsigned chunk = 30 * 1024 * 1024;
+
+      nchars = 0;
+      while (count > 0)
+        {
+          unsigned this_chunk = count < chunk ? count : chunk;
+          int n = _write (fd, p, this_chunk);
+
+          nchars += n;
+          if (n < 0)
+            {
+              nchars = n;
+              break;
+            }
+          else if (n < this_chunk)
+            break;
+          count -= n;
+          p += n;
+        }
+    }
 
   return nchars;
 }