[{"id":33165,"web_url":"https://patchwork.libcamera.org/comment/33165/","msgid":"<20250124191119.GG13689@pendragon.ideasonboard.com>","date":"2025-01-24T19:11:19","subject":"Re: [RFC PATCH v1 5/7] libcamera: base: log: Use `std::string_view`\n\tto avoid some copies","submitter":{"id":2,"url":"https://patchwork.libcamera.org/api/people/2/","name":"Laurent Pinchart","email":"laurent.pinchart@ideasonboard.com"},"content":"Hi Barnabás,\n\nThank you for the patch.\n\nOn Tue, Jan 21, 2025 at 06:56:07PM +0000, Barnabás Pőcze wrote:\n> Use `std::string_view` to avoid some largely unnecessary copies, and\n> to make string comparisong potentially faster by eliminating repeated\n> `strlen()` calls.\n> \n> Signed-off-by: Barnabás Pőcze \n\nReviewed-by: Laurent Pinchart \n\n> ---\n> include/libcamera/base/log.h | 5 +++--\n> src/libcamera/base/log.cpp | 25 +++++++++++++------------\n> 2 files changed, 16 insertions(+), 14 deletions(-)\n> \n> diff --git a/include/libcamera/base/log.h b/include/libcamera/base/log.h\n> index 89f707e54..9c7775660 100644\n> --- a/include/libcamera/base/log.h\n> +++ b/include/libcamera/base/log.h\n> @@ -9,6 +9,7 @@\n> \n> #include \n> #include \n> +#include \n> \n> #include \n> \n> @@ -29,7 +30,7 @@ enum LogSeverity {\n> class LogCategory\n> {\n> public:\n> -\tstatic LogCategory *create(const char *name);\n> +\tstatic LogCategory *create(std::string_view name);\n> \n> \tconst std::string &name() const { return name_; }\n> \tLogSeverity severity() const { return severity_.load(std::memory_order_relaxed); }\n> @@ -38,7 +39,7 @@ public:\n> \tstatic const LogCategory &defaultCategory();\n> \n> private:\n> -\texplicit LogCategory(const char *name);\n> +\texplicit LogCategory(std::string_view name);\n> \n> \tconst std::string name_;\n> \n> diff --git a/src/libcamera/base/log.cpp b/src/libcamera/base/log.cpp\n> index 795260b0a..78db4990c 100644\n> --- a/src/libcamera/base/log.cpp\n> +++ b/src/libcamera/base/log.cpp\n> @@ -15,6 +15,7 @@\n> #include \n> #include \n> #include \n> +#include \n> #include \n> #include \n> #include \n> @@ -313,11 +314,11 @@ private:\n> \n> \tvoid parseLogFile();\n> \tvoid parseLogLevels();\n> -\tstatic LogSeverity parseLogLevel(const std::string &level);\n> +\tstatic LogSeverity parseLogLevel(std::string_view level);\n> \n> \tfriend LogCategory;\n> \tvoid registerCategory(LogCategory *category);\n> -\tLogCategory *findCategory(const char *name) const;\n> +\tLogCategory *findCategory(std::string_view name) const;\n> \n> \tstatic bool destroyed_;\n> \n> @@ -642,17 +643,17 @@ void Logger::parseLogLevels()\n> \t\tif (!len)\n> \t\t\tcontinue;\n> \n> -\t\tstd::string category;\n> -\t\tstd::string level;\n> +\t\tstd::string_view category;\n> +\t\tstd::string_view level;\n> \n> \t\tconst char *colon = static_cast(memchr(pair, ':', len));\n> \t\tif (!colon) {\n> \t\t\t/* 'x' is a shortcut for '*:x'. */\n> \t\t\tcategory = \"*\";\n> -\t\t\tlevel = std::string(pair, len);\n> +\t\t\tlevel = std::string_view(pair, len);\n> \t\t} else {\n> -\t\t\tcategory = std::string(pair, colon - pair);\n> -\t\t\tlevel = std::string(colon + 1, comma - colon - 1);\n> +\t\t\tcategory = std::string_view(pair, colon - pair);\n> +\t\t\tlevel = std::string_view(colon + 1, comma - colon - 1);\n> \t\t}\n> \n> \t\t/* Both the category and the level must be specified. */\n> @@ -663,7 +664,7 @@ void Logger::parseLogLevels()\n> \t\tif (severity == LogInvalid)\n> \t\t\tcontinue;\n> \n> -\t\tlevels_.push_back({ category, severity });\n> +\t\tlevels_.emplace_back(category, severity);\n> \t}\n> }\n> \n> @@ -677,7 +678,7 @@ void Logger::parseLogLevels()\n> *\n> * \\return The log severity, or LogInvalid if the string is invalid\n> */\n> -LogSeverity Logger::parseLogLevel(const std::string &level)\n> +LogSeverity Logger::parseLogLevel(std::string_view level)\n> {\n> \tstatic const char *const names[] = {\n> \t\t\"DEBUG\",\n> @@ -744,7 +745,7 @@ void Logger::registerCategory(LogCategory *category)\n> * \\param[in] name Name of the log category\n> * \\return The pointer to the found log category or nullptr if not found\n> */\n> -LogCategory *Logger::findCategory(const char *name) const\n> +LogCategory *Logger::findCategory(std::string_view name) const\n> {\n> \tif (auto it = std::find_if(categories_.begin(), categories_.end(),\n> \t\t\t\t [name](auto c) { return c->name() == name; });\n> @@ -788,7 +789,7 @@ LogCategory *Logger::findCategory(const char *name) const\n> *\n> * \\return The pointer to the LogCategory\n> */\n> -LogCategory *LogCategory::create(const char *name)\n> +LogCategory *LogCategory::create(std::string_view name)\n> {\n> \tstatic Mutex mutex_;\n> \tMutexLocker locker(mutex_);\n> @@ -806,7 +807,7 @@ LogCategory *LogCategory::create(const char *name)\n> * \\brief Construct a log category\n> * \\param[in] name The category name\n> */\n> -LogCategory::LogCategory(const char *name)\n> +LogCategory::LogCategory(std::string_view name)\n> \t: name_(name), severity_(LogSeverity::LogInfo)\n> {\n> }","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 78B96BD78E\n\tfor ;\n\tFri, 24 Jan 2025 19:11:32 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id 776726855D;\n\tFri, 24 Jan 2025 20:11:31 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[213.167.242.64])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 433FD68556\n\tfor ;\n\tFri, 24 Jan 2025 20:11:30 +0100 (CET)","from pendragon.ideasonboard.com (81-175-209-231.bb.dnainternet.fi\n\t[81.175.209.231])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id 9DAD84AD;\n\tFri, 24 Jan 2025 20:10:25 +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=\"hdhlg385\"; dkim-atps=neutral","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/simple; d=ideasonboard.com;\n\ts=mail; t=1737745825;\n\tbh=ISMxmzKXvUCHPX/XxrjuE7IMiYua+mVRaWdLJJfNvGg=;\n\th=Date:From:To:Cc:Subject:References:In-Reply-To:From;\n\tb=hdhlg385jpFlvnK/LN22xqqoGNvYRXRVkTELAtlHtjCpP+9WrHgPKOQPY7MmJz5pC\n\t7CBesIAERTJ1TpdBk3T+2r2MgcZMHv+bUePbG3NpIvKfEf0+AljJZqbhtxL4oMxvxp\n\tRd8Ip3d8hvMa0ZQ5onXnnme+OsX9oL9qYLkJYg8A=","Date":"Fri, 24 Jan 2025 21:11:19 +0200","From":"Laurent Pinchart ","To":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","Cc":"libcamera-devel@lists.libcamera.org","Subject":"Re: [RFC PATCH v1 5/7] libcamera: base: log: Use `std::string_view`\n\tto avoid some copies","Message-ID":"<20250124191119.GG13689@pendragon.ideasonboard.com>","References":"<20250121185554.301901-1-pobrn@protonmail.com>\n\t<20250121185554.301901-3-pobrn@protonmail.com>","MIME-Version":"1.0","Content-Type":"text/plain; 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