Cap logfile size

See dechamps/FlexASIO#146

Author: dechamps

log.cpp

@@ -107,14 +107,40 @@ namespace dechamps_cpplog {
 		Logger(this) << "Host process: " << GetModuleName();
 	}
 
-	FileLogSink::FileLogSink(const std::filesystem::path& path) : stream(path, std::ios::app | std::ios::out) {
-		Logger(this) << "Logfile opened: " << path;
+	FileLogSink::FileLogSink(std::filesystem::path path, Options options) : path(std::move(path)), options(std::move(options)), stream(this->path, std::ios::app | std::ios::out) {
+		Logger(this) << "Logfile opened: " << this->path;
+		CheckSize();
 	}
 
 	FileLogSink::~FileLogSink() {
 		Logger(this) << "Closing logfile";
 	}
 
+	void FileLogSink::Write(const std::string_view str) {
+		if (!stream.is_open()) return;
+
+		stream_sink.Write(str);
+
+		const auto size = str.size();
+		if (size >= bytesRemainingUntilSizeCheck) CheckSize();
+		else bytesRemainingUntilSizeCheck -= size;
+	}
+
+	void FileLogSink::CheckSize() {
+		bytesRemainingUntilSizeCheck = (std::numeric_limits<uintmax_t>::max)();
+
+		const auto sizeBytes = std::filesystem::file_size(path);
+		const auto maxSizeBytes = options.maxSizeBytes;
+		Logger(this) << "Current log file size is " << sizeBytes << " bytes (maximum allowed: " << maxSizeBytes << " bytes)";
+
+		if (sizeBytes < maxSizeBytes) {
+			bytesRemainingUntilSizeCheck = options.sizeCheckPeriodBytes;
+			return;
+		}
+		Logger(this) << "Closing logfile as the maximum size is exceeded";
+		stream.close();
+	}
+
 	void ThreadSafeLogSink::Write(const std::string_view str) {
 		std::scoped_lock lock(mutex);
 		backend.Write(str);

log.h

@@ -38,14 +38,24 @@ namespace dechamps_cpplog {
 
 	class FileLogSink final : public LogSink {
 	public:
-		FileLogSink(const std::filesystem::path& path);
+		struct Options final {
+			uintmax_t maxSizeBytes = 1 * 1024 * 1024 * 1024;
+			uintmax_t sizeCheckPeriodBytes = std::max<uintmax_t>(maxSizeBytes / 10, 1);
+		};
+
+		FileLogSink(std::filesystem::path path, Options options = {});
 		~FileLogSink();
 
-		void Write(const std::string_view str) override { stream_sink.Write(str); }
+		void Write(const std::string_view str) override;
 
 	private:
+		void CheckSize();
+		
+		const std::filesystem::path path;
+		Options options;
 		std::ofstream stream;
 		StreamLogSink stream_sink{ stream };
+		uintmax_t bytesRemainingUntilSizeCheck = (std::numeric_limits<uintmax_t>::max)();
 	};
 
 	class ThreadSafeLogSink final : public LogSink {