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

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.

For the test:
Co-authored-by: aetonsi <18366087+aetonsi@users.noreply.github.com>

Closes GH-10492.

NEWS

@@ -24,6 +24,8 @@ PHP                                                                        NEWS
     source file). (ilutov)
 
 - Streams:
+  . Fixed bug GH-10031 ([Stream] STREAM_NOTIFY_PROGRESS over HTTP emitted
+    irregularly for last chunk of data). (nielsdos)
   . Fixed bug GH-11175 (Stream Socket Timeout). (nielsdos)
   . Fixed bug GH-11177 (ASAN UndefinedBehaviorSanitizer when timeout = -1
     passed to stream_socket_accept/stream_socket_client). (nielsdos)

ext/standard/http_fopen_wrapper.c

@@ -955,6 +955,13 @@ out:
 		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;

ext/standard/tests/streams/gh10031.phpt

@@ -0,0 +1,52 @@
+--TEST--
+GH-10031 ([Stream] STREAM_NOTIFY_PROGRESS over HTTP emitted irregularly for last chunk of data)
+--SKIPIF--
+<?php
+if (getenv("SKIP_SLOW_TESTS")) die("skip slow test");
+?>
+--INI--
+allow_url_fopen=1
+--CONFLICTS--
+server
+--FILE--
+<?php
+
+$serverCode = <<<'CODE'
+$fsize = 1000;
+$chunksize = 99;
+$chunks = floor($fsize / $chunksize); // 10 chunks * 99 bytes
+$lastchunksize = $fsize - $chunksize * $chunks; // 1 chunk * 10 bytes
+
+header("Content-Length: " . $fsize);
+flush();
+for ($chunk = 1; $chunk <= $chunks; $chunk++) {
+    echo str_repeat('x', $chunksize);
+    @ob_flush();
+    usleep(50 * 1000);
+}
+
+echo str_repeat('x', $lastchunksize);
+CODE;
+
+include __DIR__."/../../../../sapi/cli/tests/php_cli_server.inc";
+php_cli_server_start($serverCode, null, []);
+
+$context = stream_context_create(['http' => ['ignore_errors' => true,]]);
+$lastBytesTransferred = 0;
+stream_context_set_params($context, ['notification' => function ($code, $s, $m, $mc, $bytes_transferred, $bytes_max)
+use (&$lastBytesTransferred) {
+    if ($code === STREAM_NOTIFY_FILE_SIZE_IS) echo "expected filesize=$bytes_max".PHP_EOL;
+    $lastBytesTransferred = $bytes_transferred;
+    @ob_flush();
+}]);
+
+$get = file_get_contents("http://".PHP_CLI_SERVER_ADDRESS, false, $context);
+
+echo "got filesize=" . strlen($get) . PHP_EOL;
+var_dump($lastBytesTransferred);
+
+?>
+--EXPECT--
+expected filesize=1000
+got filesize=1000
+int(1000)