Do non-blocking reads from pipes in the content-length filter.

Changes with Apache 2.0.20-dev

  *) Get non-blocking CGI pipe reads working with the bucket brigades.

     [Bill Stoddard]

  *) Fix seg fault on Windows when serving files cached with mod_file_cache.

     [Bill Stoddard]

    APR_BRIGADE_FOREACH(e, b) {

        const char *ignored;

        apr_size_t length;

        apr_size_t len;

        if (APR_BUCKET_IS_EOS(e) || APR_BUCKET_IS_FLUSH(e)) {

            send_it = 1;

        }

        if (e->length == -1) { /* if length unknown */

            rv = apr_bucket_read(e, &ignored, &length, APR_BLOCK_READ);

            rv = apr_bucket_read(e, &ignored, &len, APR_NONBLOCK_READ);

            if (rv == APR_EAGAIN) {

                /* If the protocol level implies support for chunked encoding, 

                 * flush the filter chain to the network then do a blocking 

                 * read. This is replicating the behaviour of ap_send_fb

                 * in Apache 1.3.

                 */

                if (r->proto_num >= HTTP_VERSION(1,1)) {

                    apr_bucket_brigade *split;

                    split = apr_brigade_split(b, e);

                    rv = ap_fflush(f, b);

                    if (rv != APR_SUCCESS)

                        return rv;

                    b = split;

                    ctx->curr_len = 0;

                }

                rv = apr_bucket_read(e, &ignored, &len, APR_BLOCK_READ);

            }

            if (rv != APR_SUCCESS) {

                ap_log_rerror(APLOG_MARK, APLOG_ERR, rv, r, "ap_content_length_filter: "

                              "apr_bucket_read() failed");

                return rv;

            }

        }

        else {

            length = e->length;

            len = e->length;

        }

        ctx->curr_len += length;

        r->bytes_sent += length;

        ctx->curr_len += len;

        r->bytes_sent += len;

    }

    if ((ctx->curr_len < AP_MIN_BYTES_TO_WRITE) && !send_it) {