szaszm commented on a change in pull request #1057:
URL: https://github.com/apache/nifi-minifi-cpp/pull/1057#discussion_r633704910
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File path: libminifi/include/core/logging/Logger.h
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@@ -68,13 +69,32 @@ inline T conditional_conversion(T t) {
}
template<typename ... Args>
-inline std::string format_string(char const* format_str, Args&&... args) {
- char buf[LOG_BUFFER_SIZE];
- std::snprintf(buf, LOG_BUFFER_SIZE, format_str,
conditional_conversion(std::forward<Args>(args))...);
- return std::string(buf);
+inline std::string format_string(int max_size, char const* format_str,
Args&&... args) {
+ if (0 <= max_size && max_size <= LOG_BUFFER_SIZE) {
+ // use static buffer
+ char buf[LOG_BUFFER_SIZE + 1];
+ std::snprintf(buf, max_size + 1, format_str,
conditional_conversion(std::forward<Args>(args))...);
+ return std::string(buf);
+ }
+ // use dynamically allocated buffer
+ if (max_size < 0) {
+ // query what buffer size we need
+ int size_needed = std::snprintf(nullptr, 0, format_str,
conditional_conversion(std::forward<Args>(args))...);
Review comment:
`snprintf` incurs the full cost of formatting even if the buffer is
`nullptr` AFAIK. I would prefer a conservative sized stack buffer with fallback
to allocation, so that at least sometimes it can be faster.
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