I think I finally found the culprit. At first I thought it was the
core_output_filter, but it turns out that emulate_sendfile (incorrectly)
assumes that it is at the beginning of the file even when it's not.
The attached patch works here when I have the combo of buckets as
described below. The patch is against 2.0.49.
On Thu, 2003-08-07 at 21:49, Bojan Smojver wrote:
> Greetings everyone, it has been a while since I posted my ramblings
> about mod_logio... Anyway, it's that time of the year again :-)
>
> I'm working on a new module and I have hit a strange problem in relation
> to core_output_filter, which is as far as I can see affecting my output.
>
> Let's say I have a file that contains 300 bytes of something I'm
> interested in, then 10 bytes of rubbish, then 300 bytes of good stuff
> again and so on. The reason I'm picking 300 bytes here is because this
> number is greater than AP_MIN_SENDFILE_BYTES, which is 256.
>
> So, I build up a brigade that looks like this:
>
> FILE - POOL - FILE - POOL - FILE - EOS
>
> The POOL buckets contains something useful instead of 10 bytes of
> rubbish that I would normally find in the file. The file buckets are
> chunks of the same file that I'm interested in.
>
> When I pass this to output filters in my handler with
> ap_pass_brigade(r->output_filters,bb), I'm getting completely random
> output from. In other words, offsets of FILE buckets are completely
> screwed or buckets down show up at all.
>
> If I, however, build a brigade like this:
>
> FILE - FLUSH - POOL - FILE - FLUSH - POOL - FILE - FLUSH - EOS
>
> then it all works fine. Also, if the good parts of my file are below 256
> bytes (or if I increase AP_MIN_SENDFILE_BYTES above the threshold),
> there are no problems at all.
>
> I was testing this all this on 2.0.46, Red Hat Linux 9. Has anyone else
> observed anything like that? Has anything like that been fixed lately?
>
> Or am I simply doing something really stupid...
--
Bojan
diff -ruN httpd-2.0.49-vanilla/server/core.c httpd-2.0.49/server/core.c
--- httpd-2.0.49-vanilla/server/core.c 2004-03-09 09:54:20.000000000 +1100
+++ httpd-2.0.49/server/core.c 2004-03-22 18:56:29.000000000 +1100
@@ -2975,7 +2975,7 @@
}
/* Seek the file to 'offset' */
- if (offset != 0 && rv == APR_SUCCESS) {
+ if (offset >= 0 && rv == APR_SUCCESS) {
rv = apr_file_seek(fd, APR_SET, &offset);
}
