{"id":24908,"url":"https://patchwork.libcamera.org/api/patches/24908/?format=json","web_url":"https://patchwork.libcamera.org/patch/24908/","project":{"id":1,"url":"https://patchwork.libcamera.org/api/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":"<20251030165816.1095180-6-barnabas.pocze@ideasonboard.com>","date":"2025-10-30T16:57:59","name":"[RFC,v3,05/22] libcamera: base: cxx20: Add `has_single_bit()`","commit_ref":null,"pull_url":null,"state":"superseded","archived":false,"hash":"cf573de55999ae9aeab89592ed1f3ad655624383","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/people/216/?format=json","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"delegate":null,"mbox":"https://patchwork.libcamera.org/patch/24908/mbox/","series":[{"id":5545,"url":"https://patchwork.libcamera.org/api/series/5545/?format=json","web_url":"https://patchwork.libcamera.org/project/libcamera/list/?series=5545","date":"2025-10-30T16:57:54","name":"libcamera: Add `MetadataList`","version":3,"mbox":"https://patchwork.libcamera.org/series/5545/mbox/"}],"comments":"https://patchwork.libcamera.org/api/patches/24908/comments/","check":"pending","checks":"https://patchwork.libcamera.org/api/patches/24908/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 15D33C3259\n\tfor ;\n\tThu, 30 Oct 2025 16:58:35 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 828DE608F4;\n\tThu, 30 Oct 2025 17:58:29 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 0CC26608DD\n\tfor ;\n\tThu, 30 Oct 2025 17:58:22 +0100 (CET)","from pb-laptop.local (185.221.140.239.nat.pool.zt.hu\n\t[185.221.140.239])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id DDE2218E5;\n\tThu, 30 Oct 2025 17:56:31 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; dkim=pass (1024-bit key;\n\tunprotected) header.d=ideasonboard.com header.i=@ideasonboard.com\n\theader.b=\"I6ClU1co\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1761843392;\n\tbh=HciZSJ8c9rrJbGOx9JzK+X8ACBgX7TlUyIG8STiQ8As=;\n\th=From:To:Cc:Subject:Date:In-Reply-To:References:From;\n\tb=I6ClU1cor3yL5GN0TOgC+N4PzT3L0hWZyvBN4O9rvJ3hA6X1z6x2fxvdlhEaCRYFG\n\t2US9fOcspPUHmR2GrW4pndlkFvb0z+kw173chh/tw5iuCQJev/l86d8mJPAVhc1Q8H\n\tTN/G2ntXlXE6EAaHtLY0VlHoAzNBKjlIOS6ROxnQ=","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","To":"libcamera-devel@lists.libcamera.org","Cc":"Paul Elder ","Subject":"[RFC PATCH v3 05/22] libcamera: base: cxx20: Add `has_single_bit()`","Date":"Thu, 30 Oct 2025 17:57:59 +0100","Message-ID":"<20251030165816.1095180-6-barnabas.pocze@ideasonboard.com>","X-Mailer":"git-send-email 2.51.1","In-Reply-To":"<20251030165816.1095180-1-barnabas.pocze@ideasonboard.com>","References":"<20251030165816.1095180-1-barnabas.pocze@ideasonboard.com>","MIME-Version":"1.0","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"8bit","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":"`has_single_bit()` checks if the given unsigned integer has a single\nbit set, that is, whether the number is a power of two or not.\n\nNot all requirements of the C++20 standard are implemented.\n\nSee https://en.cppreference.com/w/cpp/numeric/has_single_bit\n\nSigned-off-by: Barnabás Pőcze \nReviewed-by: Paul Elder \n---\n include/libcamera/base/internal/cxx20.h | 16 ++++++++++++++++\n 1 file changed, 16 insertions(+)","diff":"diff --git a/include/libcamera/base/internal/cxx20.h b/include/libcamera/base/internal/cxx20.h\nindex 1f4caf56f8..d47168a70a 100644\n--- a/include/libcamera/base/internal/cxx20.h\n+++ b/include/libcamera/base/internal/cxx20.h\n@@ -7,6 +7,8 @@\n \n #pragma once\n \n+#include \n+\n /**\n * \\internal\n * \\file cxx20.h\n@@ -39,4 +41,18 @@ template struct type_identity {\n */\n template using type_identity_t = typename type_identity::type;\n \n+/**\n+ * \\internal\n+ * \\brief std::has_single_bit()\n+ *\n+ * Implementation of std::has_single_bit() for C++17.\n+ */\n+template\n+constexpr bool has_single_bit(T x) noexcept\n+{\n+\tstatic_assert(std::is_unsigned_v);\n+\n+\treturn x != 0 && (x & (x - 1)) == 0;\n+}\n+\n } /* namespace libcamera::internal::cxx20 */\n","prefixes":["RFC","v3","05/22"]}