96 lines
3.3 KiB
C++
96 lines
3.3 KiB
C++
// Copyright 2019 The Dawn Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef SRC_DAWN_COMMON_LOG_H_
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#define SRC_DAWN_COMMON_LOG_H_
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// Dawn targets shouldn't use iostream or printf directly for several reasons:
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// - iostream adds static initializers which we want to avoid.
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// - printf and iostream don't show up in logcat on Android so printf debugging doesn't work but
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// log-message debugging does.
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// - log severity helps provide intent compared to a printf.
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//
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// Logging should in general be avoided: errors should go through the regular WebGPU error reporting
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// mechanism and others form of logging should (TODO: eventually) go through the logging dependency
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// injection, so for example they show up in Chromium's about:gpu page. Nonetheless there are some
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// cases where logging is necessary and when this file was first introduced we needed to replace all
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// uses of iostream so we could see them in Android's logcat.
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//
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// Regular logging is done using the [Debug|Info|Warning|Error]Log() function this way:
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//
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// InfoLog() << things << that << ostringstream << supports; // No need for a std::endl or "\n"
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//
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// It creates a LogMessage object that isn't stored anywhere and gets its destructor called
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// immediately which outputs the stored ostringstream in the right place.
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//
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// This file also contains DAWN_DEBUG for "printf debugging" which works on Android and
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// additionally outputs the file, line and function name. Use it this way:
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//
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// // Pepper this throughout code to get a log of the execution
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// DAWN_DEBUG();
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//
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// // Get more information
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// DAWN_DEBUG() << texture.GetFormat();
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#include <sstream>
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namespace dawn {
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// Log levels mostly used to signal intent where the log message is produced and used to route
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// the message to the correct output.
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enum class LogSeverity {
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Debug,
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Info,
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Warning,
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Error,
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};
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// Essentially an ostringstream that will print itself in its destructor.
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class LogMessage {
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public:
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explicit LogMessage(LogSeverity severity);
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~LogMessage();
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LogMessage(LogMessage&& other);
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LogMessage& operator=(LogMessage&& other);
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template <typename T>
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LogMessage& operator<<(T&& value) {
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mStream << value;
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return *this;
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}
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private:
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LogMessage(const LogMessage& other) = delete;
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LogMessage& operator=(const LogMessage& other) = delete;
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LogSeverity mSeverity;
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std::ostringstream mStream;
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};
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// Short-hands to create a LogMessage with the respective severity.
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LogMessage DebugLog();
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LogMessage InfoLog();
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LogMessage WarningLog();
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LogMessage ErrorLog();
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// DAWN_DEBUG is a helper macro that creates a DebugLog and outputs file/line/function
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// information
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LogMessage DebugLog(const char* file, const char* function, int line);
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#define DAWN_DEBUG() ::dawn::DebugLog(__FILE__, __func__, __LINE__)
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} // namespace dawn
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#endif // SRC_DAWN_COMMON_LOG_H_
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