cache millis in full_formatter

include/spdlog/details/fmt_helper.h

@@ -8,13 +8,16 @@
 namespace spdlog {
 namespace details {
 namespace fmt_helper {
-inline void append_str(const std::string &str, fmt::memory_buffer &dest)
+
+template <size_t Buffer_Size>
+inline void append_str(const std::string &str, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
     auto *str_ptr = str.data();
     dest.append(str_ptr, str_ptr + str.size());
 }
 
-inline void append_c_str(const char *c_str, fmt::memory_buffer &dest)
+template <size_t Buffer_Size>
+inline void append_c_str(const char *c_str, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
     char ch;
     while ((ch = *c_str) != '\0')
@@ -24,21 +27,22 @@ inline void append_c_str(const char *c_str, fmt::memory_buffer &dest)
     }
 }
 
-template<size_t N1, size_t N2>
-inline void append_buf(const fmt::basic_memory_buffer<char, N1> &buf, fmt::basic_memory_buffer<char, N2> &dest)
+template<size_t Buffer_Size1, size_t Buffer_Size2>
+inline void append_buf(const fmt::basic_memory_buffer<char, Buffer_Size1> &buf, fmt::basic_memory_buffer<char, Buffer_Size2> &dest)
 {
     auto *buf_ptr = buf.data();
     dest.append(buf_ptr, buf_ptr + buf.size());
 }
 
-template<typename T>
-inline void append_int(T n, fmt::memory_buffer &dest)
+template<typename T, size_t Buffer_Size>
+inline void append_int(T n, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
     fmt::format_int i(n);
     dest.append(i.data(), i.data() + i.size());
 }
 
-inline void pad2(int n, fmt::memory_buffer &dest)
+template <size_t Buffer_Size>
+inline void pad2(int n, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
     if (n > 99)
     {
@@ -61,7 +65,8 @@ inline void pad2(int n, fmt::memory_buffer &dest)
     fmt::format_to(dest, "{:02}", n);
 }
 
-inline void pad3(int n, fmt::memory_buffer &dest)
+template <size_t Buffer_Size>
+inline void pad3(int n, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
     if (n > 99)
     {
@@ -86,7 +91,8 @@ inline void pad3(int n, fmt::memory_buffer &dest)
     fmt::format_to(dest, "{:03}", n);
 }
 
-inline void pad6(size_t n, fmt::memory_buffer &dest)
+template <size_t Buffer_Size>
+inline void pad6(size_t n, fmt::basic_memory_buffer<char, Buffer_Size> &dest)
 {
     // todo: maybe replace this implementation with
     // pad3(n / 1000, dest);

include/spdlog/details/pattern_formatter.h

@@ -120,7 +120,16 @@ class c_formatter SPDLOG_FINAL : public flag_formatter
 {
     void format(const details::log_msg &, const std::tm &tm_time, fmt::memory_buffer &dest) override
     {
-        fmt::format_to(dest, "{} {} {} ", days[tm_time.tm_wday], months[tm_time.tm_mon], tm_time.tm_mday); //
+        //fmt::format_to(dest, "{} {} {} ", days[tm_time.tm_wday], months[tm_time.tm_mon], tm_time.tm_mday);
+        // date
+        fmt_helper::append_str(days[tm_time.tm_wday], dest);
+        dest.push_back(' ');
+        fmt_helper::append_str(months[tm_time.tm_mon], dest);
+        dest.push_back(' ');
+        fmt_helper::append_int(tm_time.tm_mday, dest);
+        dest.push_back(' ');
+        // time
+
         fmt_helper::pad2(tm_time.tm_hour, dest);
         dest.push_back(':');
         fmt_helper::pad2(tm_time.tm_min, dest);
@@ -366,7 +375,6 @@ class t_formatter SPDLOG_FINAL : public flag_formatter
 {
     void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override
     {
-
         fmt_helper::pad6(msg.thread_id, dest);
     }
 };
@@ -385,7 +393,6 @@ class i_formatter SPDLOG_FINAL : public flag_formatter
 {
     void format(const details::log_msg &msg, const std::tm &, fmt::memory_buffer &dest) override
     {
-
         fmt_helper::pad6(msg.msg_id, dest);
     }
 };
@@ -457,39 +464,48 @@ class full_formatter SPDLOG_FINAL : public flag_formatter
     {
 #ifndef SPDLOG_NO_DATETIME
 
-        // each second cache the header
+        // cache the date/time part for the next second.
         auto duration = msg.time.time_since_epoch();
-        auto seconds = std::chrono::duration_cast<std::chrono::seconds>(duration).count();
-        if (cached_header_.size() == 0 || cached_seconds_ts_ != seconds)
+        std::chrono::seconds seconds = std::chrono::duration_cast<std::chrono::seconds>(duration);
+
+        if (cache_timestamp_ != seconds || cached_datetime_.size() == 0)
         {
-            cached_header_.resize(0);
-            cached_header_.push_back('[');
-            fmt_helper::append_int(tm_time.tm_year + 1900, cached_header_);
-            cached_header_.push_back('-');
+            cached_datetime_.resize(0);
+            cached_datetime_.push_back('[');
+            fmt_helper::append_int(tm_time.tm_year + 1900, cached_datetime_);
+            cached_datetime_.push_back('-');
 
-            fmt_helper::pad2(tm_time.tm_mon + 1, cached_header_);
-            cached_header_.push_back('-');
+            fmt_helper::pad2(tm_time.tm_mon + 1, cached_datetime_);
+            cached_datetime_.push_back('-');
 
-            fmt_helper::pad2(tm_time.tm_mday, cached_header_);
-            cached_header_.push_back(' ');
+            fmt_helper::pad2(tm_time.tm_mday, cached_datetime_);
+            cached_datetime_.push_back(' ');
 
-            fmt_helper::pad2(tm_time.tm_hour, cached_header_);
-            cached_header_.push_back(':');
+            fmt_helper::pad2(tm_time.tm_hour, cached_datetime_);
+            cached_datetime_.push_back(':');
 
-            fmt_helper::pad2(tm_time.tm_min, cached_header_);
-            cached_header_.push_back(':');
+            fmt_helper::pad2(tm_time.tm_min, cached_datetime_);
+            cached_datetime_.push_back(':');
 
-            fmt_helper::pad2(tm_time.tm_sec, cached_header_);
-            cached_header_.push_back('.');
+            fmt_helper::pad2(tm_time.tm_sec, cached_datetime_);
+            cached_datetime_.push_back('.');
 
-            cached_seconds_ts_ = seconds;
+            cache_timestamp_ = seconds;
         }
-        fmt_helper::append_buf(cached_header_, dest);
+        fmt_helper::append_buf(cached_datetime_, dest);
 
+        // cache the millis part for the next milli.
         auto millis = std::chrono::duration_cast<std::chrono::milliseconds>(duration).count() % 1000;
-        fmt_helper::pad3(static_cast<int>(millis), dest);
-        dest.push_back(']');
-        dest.push_back(' ');
+        if(millis != millis_cache_timestamp_ || cached_millis_.size() == 0)
+        {
+            cached_millis_.resize(0);
+            fmt_helper::pad3(millis, cached_millis_);
+            cached_millis_.push_back(']');
+            cached_millis_.push_back(' ');
+            millis_cache_timestamp_ = millis;
+        }
+
+        fmt_helper::append_buf(cached_millis_, dest);
 #else // no datetime needed
         (void)tm_time;
 #endif
@@ -512,8 +528,10 @@ class full_formatter SPDLOG_FINAL : public flag_formatter
     }
 
 private:
-    std::chrono::seconds::rep cached_seconds_ts_{0};
-    fmt::memory_buffer cached_header_;
+    std::chrono::seconds cache_timestamp_ {0};
+    std::chrono::milliseconds::rep millis_cache_timestamp_ {0};
+    fmt::basic_memory_buffer<char, 128> cached_datetime_;
+    fmt::basic_memory_buffer<char, 8> cached_millis_;
 };
 
 } // namespace details