Fix GH-10031: [Stream] STREAM_NOTIFY_PROGRESS over HTTP emitted irregularly for last chunk of data

Fixes GH-10031

It's possible that the server already sent in more data than just the headers.
Since the stream only accepts progress increments after the headers are
processed, the already read data is never added to the process.
We account for this by adjusting the progress counter by the difference of
already read header data and the body.

Author: nielsdos

ext/standard/http_fopen_wrapper.c

@@ -955,6 +955,13 @@ static php_stream *php_stream_url_wrap_http_ex(php_stream_wrapper *wrapper,
 		if (transfer_encoding) {
 			php_stream_filter_append(&stream->readfilters, transfer_encoding);
 		}
+
+		/* It's possible that the server already sent in more data than just the headers.
+		 * We account for this by adjusting the progress counter by the difference of
+		 * already read header data and the body. */
+		if (stream->writepos > stream->readpos) {
+			php_stream_notify_progress_increment(context, stream->writepos - stream->readpos, 0);
+		}
 	}
 
 	return stream;