[Dovecot] A view quirks

[Andreas Jaekel]

Aloha.


>here's fstream->file which tells if it's a regular file :)

Oooh, nice!  But does that work outside ostream.c? :)





>They're not dup()ed, they just use the same file descriptors. But ..
>hmm. that would be possible, but that's still quite a lot of code for
>cases which are rarely needed..

But it'd be clean and the way to avoid the largest number of
syscalls if pread/pwrite are not an option.



> > Another possible solution is to change output to always use
> > pwrite(), avoiding the need for seeks completly.
>
>Changing ostream to use pwrite() would require replacing the one
>writev() call too with multiple pwrite()s, not nice .. :)
>
>How about: [...]

Thank you for the patch.  It worked, except for two little things:

1. I don't use Linux, so the #define for pseek broke
the compile and
2. I had to remove the lseek() call in _read(), which was
the whole point in using pread()   :)   In mbox folders
this wouldn't have mattered since the loop is written in
a way that assumes mail 4 starts exactly where mail 3 ends,
which is not true for my case.

This worked for me:


--- ../dovecot/src/lib/istream-file.c   Tue Aug 26 23:18:16 2003
+++ ./src/lib/istream-file.c    Tue Oct 21 16:18:55 2003
@@ -169,7 +169,15 @@
                         return -1;
                 }

-               ret = read(stream->fd, stream->w_buffer + stream->pos, size);
+               if (fstream->file) {
+                       ret = pread(stream->fd,
+                       stream->w_buffer + stream->pos, size,
+                       stream->istream.start_offset +
+                       stream->istream.v_offset);
+               } else {
+                       ret = read(stream->fd,
+                       stream->w_buffer + stream->pos, size);
+               }
                 if (ret == 0) {
                         /* EOF */
                         stream->istream.stream_errno = 0;
@@ -228,7 +236,7 @@
                 stream->istream.stream_errno = EOVERFLOW;
                 ret = -1;
         } else {
-               ret = lseek(stream->fd, (off_t)real_offset, SEEK_SET);
+               ret = (off_t)real_offset;
                 if (ret < 0)
                         stream->istream.stream_errno = errno;
                 else if (ret != (off_t)real_offset) {