{"id":19954,"url":"https://patchwork.libcamera.org/api/1.1/patches/19954/?format=json","web_url":"https://patchwork.libcamera.org/patch/19954/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/1.1/projects/1/?format=json","name":"libcamera","link_name":"libcamera","list_id":"libcamera_core","list_email":"libcamera-devel@lists.libcamera.org","web_url":"","scm_url":"","webscm_url":""},"msgid":"<20240425160317.326458-1-pobrn@protonmail.com>","date":"2024-04-25T16:03:19","name":"[v2] treewide: Query list of cameras just once","commit_ref":null,"pull_url":null,"state":"superseded","archived":false,"hash":"234d30fe5f2b2ab48da376ecdbd19695000a0b15","submitter":{"id":133,"url":"https://patchwork.libcamera.org/api/1.1/people/133/?format=json","name":"Pőcze Barnabás","email":"pobrn@protonmail.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/19954/mbox/","series":[{"id":4274,"url":"https://patchwork.libcamera.org/api/1.1/series/4274/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=4274","date":"2024-04-25T16:03:19","name":"[v2] treewide: Query list of cameras just once","version":2,"mbox":"https://patchwork.libcamera.org/series/4274/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/19954/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/19954/checks/","tags":{},"headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 7338CC3220\n\tfor ;\n\tThu, 25 Apr 2024 16:03:27 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 905B461B43;\n\tThu, 25 Apr 2024 18:03:26 +0200 (CEST)","from mail-40133.protonmail.ch (mail-40133.protonmail.ch\n\t[185.70.40.133])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 653A461A9B\n\tfor ;\n\tThu, 25 Apr 2024 18:03:24 +0200 (CEST)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (2048-bit key;\n\tunprotected) header.d=protonmail.com header.i=@protonmail.com\n\theader.b=\"lc9xcQ1d\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=protonmail.com;\n\ts=protonmail3; t=1714061003; x=1714320203;\n\tbh=cBci5P9lqCSMjhbRtuANGmsj65JaAPeVZqEZrY9vfUw=;\n\th=Date:To:From:Subject:Message-ID:Feedback-ID:From:To:Cc:Date:\n\tSubject:Reply-To:Feedback-ID:Message-ID:BIMI-Selector;\n\tb=lc9xcQ1dKvvCIZK3g+Mv+yK8o/KEAAZwpYgrfxH2GL2/5XdgXgUMWMYAjdFKthutX\n\tfohKnTNQR0kTxZZ6sU/pXCr7l7S6JTpjnqIjXJPRcZEvMwfLK+mMrMEn42IsbLfjCZ\n\te8d5ku24CzPwavMeVe08juaCm2A62rOo/ikK4aQ3i8ABC0Lvjh4wC7BPUSSTBdqzSD\n\tC6R7UVP8leWhL6Vfi7pzN84P+9zzUDUPbkbzcSYzEuns59h2OZmE8f0GAuepxWgP1b\n\tMH8JtIOPYZ8wTI/AIxFoMta51CWvsdnATunHTwZ8pM1m8KXNcxLcaP5jR1CX4Z9ZzB\n\tWjSycEE30edGA==","Date":"Thu, 25 Apr 2024 16:03:19 +0000","To":"libcamera-devel@lists.libcamera.org","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","Subject":"[PATCH v2] treewide: Query list of cameras just once","Message-ID":"<20240425160317.326458-1-pobrn@protonmail.com>","Feedback-ID":"20568564:user:proton","X-Pm-Message-ID":"b3e1c77aaad357cfc2b27f2b2cea1cfd45751893","MIME-Version":"1.0","Content-Type":"text/plain; charset=utf-8","Content-Transfer-Encoding":"quoted-printable","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "},"content":"This is more efficient since only a single vector will be constructed,\nand furthermore, it prevents the TOCTOU issue that might arise when\nthe list of cameras changes between the two queries.\n---\n Documentation/guides/application-developer.rst | 11 ++++++-----\n src/apps/cam/camera_session.cpp | 6 ++++--\n src/gstreamer/gstlibcamerasrc.cpp | 5 +++--\n 3 files changed, 13 insertions(+), 9 deletions(-)\n\n\nbase-commit: fb74bb7df66b96dbe28702155cddfc96a1b30f78","diff":"diff --git a/Documentation/guides/application-developer.rst b/Documentation/guides/application-developer.rst\nindex 9a9905b1..e09ddfb1 100644\n--- a/Documentation/guides/application-developer.rst\n+++ b/Documentation/guides/application-developer.rst\n@@ -116,20 +116,21 @@ available.\n \n .. code:: cpp\n \n- if (cm->cameras().empty()) {\n+ auto cameras = cm->cameras();\n+ if (cameras.empty()) {\n std::cout << \"No cameras were identified on the system.\"\n << std::endl;\n cm->stop();\n return EXIT_FAILURE;\n }\n \n- std::string cameraId = cm->cameras()[0]->id();\n- camera = cm->get(cameraId);\n+ std::string cameraId = cameras[0]->id();\n \n /*\n- * Note that is equivalent to:\n- * camera = cm->cameras()[0];\n+ * Note that `camera` may be nullptr as the camera\n+ * might have disappeared in the meantime.\n */\n+ auto camera = cm->get(cameraId);\n \n Once a camera has been selected an application needs to acquire an exclusive\n lock to it so no other application can use it.\ndiff --git a/src/apps/cam/camera_session.cpp b/src/apps/cam/camera_session.cpp\nindex 8447f932..5afd087f 100644\n--- a/src/apps/cam/camera_session.cpp\n+++ b/src/apps/cam/camera_session.cpp\n@@ -39,8 +39,10 @@ CameraSession::CameraSession(CameraManager *cm,\n {\n \tchar *endptr;\n \tunsigned long index = strtoul(cameraId.c_str(), &endptr, 10);\n-\tif (*endptr == '\\0' && index > 0 && index <= cm->cameras().size())\n-\t\tcamera_ = cm->cameras()[index - 1];\n+\tauto cameras = cm->cameras();\n+\n+\tif (*endptr == '\\0' && index > 0 && index <= cameras.size())\n+\t\tcamera_ = std::move(cameras[index - 1]);\n \telse\n \t\tcamera_ = cm->get(cameraId);\n \ndiff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp\nindex f015c6d2..8613d66d 100644\n--- a/src/gstreamer/gstlibcamerasrc.cpp\n+++ b/src/gstreamer/gstlibcamerasrc.cpp\n@@ -385,13 +385,14 @@ gst_libcamera_src_open(GstLibcameraSrc *self)\n \t\t\treturn false;\n \t\t}\n \t} else {\n-\t\tif (cm->cameras().empty()) {\n+\t\tauto cameras = cm->cameras();\n+\t\tif (cameras.empty()) {\n \t\t\tGST_ELEMENT_ERROR(self, RESOURCE, NOT_FOUND,\n \t\t\t\t\t (\"Could not find any supported camera on this system.\"),\n \t\t\t\t\t (\"libcamera::CameraMananger::cameras() is empty\"));\n \t\t\treturn false;\n \t\t}\n-\t\tcam = cm->cameras()[0];\n+\t\tcam = std::move(cameras[0]);\n \t}\n \n \tGST_INFO_OBJECT(self, \"Using camera '%s'\", cam->id().c_str());\n","prefixes":["v2"]}