LogLevel: support conversion from floating-point numbers

... so that, e.g., we can set the logging from an expression value.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/buildtool/logging/log_level.hpp b/src/buildtool/logging/log_level.hpp
index 55b66790..1902e960 100644
--- a/src/buildtool/logging/log_level.hpp
+++ b/src/buildtool/logging/log_level.hpp
@@ -16,6 +16,7 @@
 #define INCLUDED_SRC_BUILDTOOL_LOGGING_LOG_LEVEL_HPP
 
 #include <algorithm>
+#include <cmath>
 #include <string>
 #include <type_traits>
 
@@ -40,6 +41,23 @@ constexpr auto kLastLogLevel = LogLevel::Trace;
                     kLastLogLevel);
 }
 
+[[nodiscard]] static inline auto ToLogLevel(double level) -> LogLevel {
+    if (level < static_cast<double>(kFirstLogLevel)) {
+        return kFirstLogLevel;
+    }
+    if (level > static_cast<double>(kLastLogLevel)) {
+        return kLastLogLevel;
+    }
+    // Now we're in range, so we can round and cast.
+    try {
+        return ToLogLevel(
+            static_cast<std::underlying_type_t<LogLevel>>(std::lround(level)));
+    } catch (...) {
+        // should not happen, but chose the most conservative value
+        return kLastLogLevel;
+    }
+}
+
 [[nodiscard]] static inline auto LogLevelToString(LogLevel level)
     -> std::string {
     switch (level) {