apr_file_flush and short writes

[Blair Zajac]

[I sent this to d...@apr.apache.org but haven't received a response. 
Thread here:
http://mail-archives.apache.org/mod_mbox/apr-dev/201102.mbox/%3cf7b1928d-d32f-48dd-b8d9-80b26906a...@orcaware.com%3E 
.  Given the importance of writing complete files for svn, could 
somebody take a look and see if this is a valid issue].

I was looking at apr_file_flush() and think I found a bug where if 
write() doesn't do a full write, then the apr_file_t will destroy and 
buffered data because it sets its internal buffer position back to 0.

Here's a patch for this:

Index: file_io/unix/readwrite.c
===================================================================
--- file_io/unix/readwrite.c    (revision 1067340)
+++ file_io/unix/readwrite.c    (working copy)
@@ -409,7 +409,11 @@
             rv = errno;
         } else {
             thefile->filePtr += written;
-            thefile->bufpos = 0;
+            if (written != thefile->bufpos)
+                memmove(thefile->buffer,
+                        thefile->buffer + written,
+                        thefile->bufpos - written);
+            thefile->bufpos -= written;
         }
     }

Beyond this, there's no a mechanism to report that all the buffered data 
didn't get into the file.  Perhaps apr_file_flush() should loop until 
the entire buffer is written or it gets a non-EINTR error?

Thanks,
Blair