ai perf: log

Author: fchn289

src/log/StrCoutFSL.hpp

@@ -5,39 +5,74 @@
  */
 // ***********************************************************************************************
 // CONSTITUTION : 1 solution of smart log,
-// - tmp log is stringstream (dyn buf)
+// - tmp log is std::string via lightweight custom streambuf (dyn buf)
 // - permanent log is cout (screen)
 // . shortcoming: multiple smart logs will mix output on screen
 // - formatted log (FSL = Formatted Smart Log)
 // . slower than unformatted smart log, but more readable
 // - derive from BaseSL is to reuse common func
 //
-// CORE: _tmpBuf (func around it)
+// CORE: sbuf_ (func around it)
 //
 // MT safe: false
 //
-// mem safe: yes if stringstream is
+// mem safe: yes
 // ***********************************************************************************************
 #pragma once
 
 #include <iostream>
-#include <sstream>  // stringstream
+#include <string>
 
 #include "BaseSL.hpp"
 
 namespace rlib
 {
+// ***********************************************************************************************
+// - lightweight streambuf that appends directly to std::string
+// - avoids std::stringbuf's bidirectional buffer & internal double-buffering overhead
+class StringStreamBuf : public std::streambuf
+{
+public:
+    const std::string& str() const noexcept { return buf_; }
+    size_t size() const noexcept { return buf_.size(); }
+
+protected:
+    int_type overflow(int_type ch) override
+    {
+        if (ch != traits_type::eof())
+            buf_ += static_cast<char>(ch);
+        return ch;
+    }
+
+    std::streamsize xsputn(const char* s, std::streamsize n) override
+    {
+        buf_.append(s, static_cast<size_t>(n));
+        return n;
+    }
+
+private:
+    std::string buf_;
+};
+
+// ***********************************************************************************************
+// - holder to ensure sbuf_ is constructed before std::ostream base
+struct StrCoutFSL_BufHolder
+{
+    StringStreamBuf sbuf_;
+};
+
 // ***********************************************************************************************
 class StrCoutFSL  // FSL = Formatted Smart Log
     : public BaseSL
-    , public std::stringstream   // for operator<<(); must not ostringstream since dump need read it!!!
+    , private StrCoutFSL_BufHolder   // must be before std::ostream to init sbuf_ first
+    , public std::ostream            // lightweight: no bidirectional stringbuf overhead
 {
 public :
+    StrCoutFSL() : std::ostream(&sbuf_) {}
     ~StrCoutFSL() noexcept;
 
-    // for gtest/etc that failure maybe after testcase destruction
-    // void forceDel() { stringstream().swap(*this); }
     void forceSave() const noexcept;
+    size_t size() const noexcept { return sbuf_.size(); }
 };
 
 // ***********************************************************************************************
@@ -54,7 +89,7 @@ StrCoutFSL::~StrCoutFSL() noexcept
 inline
 void StrCoutFSL::forceSave() const noexcept
 {
-    std::cout << rdbuf() << '\n';  // rdbuf() faster than str(); newline w/o flush faster than endl
+    std::cout << sbuf_.str() << '\n';  // direct string access; newline w/o flush faster than endl
 }
 
 }  // namespace
@@ -63,4 +98,5 @@ void StrCoutFSL::forceSave() const noexcept
 // ..........  .........   .......................................................................
 // 2006-       CSZ       - create
 // 2022-01-01  PJ & CSZ  - formal log & naming
+// 2026-03-05  AI        - replace stringstream with lightweight custom streambuf + std::string
 // ***********************************************************************************************

src/log/UniBaseLog.hpp

@@ -21,21 +21,21 @@ using LogName = std::string;
 // - mem safe: yes
 // - MT safe : yes of UniCoutLog, no of UniSmartLog
 #ifdef __FILE_NAME__  // g++12/c++20
-#define BUF(content) __FILE_NAME__ << ':' << __func__ << "():" << __LINE__ << ": " << content << std::endl
+#define BUF(content) __FILE_NAME__ << ':' << __func__ << "():" << __LINE__ << ": " << content << '\n'
 #else
-#define BUF(content)                         __func__ << "():" << __LINE__ << ": " << content << std::endl
+#define BUF(content)                         __func__ << "():" << __LINE__ << ": " << content << '\n'
 #endif
-#define INF(content) { oneLog() << "INF/" << std::this_thread::get_id() << "] " << BUF(content); }
-#define WRN(content) { oneLog() << "WRN/" << std::this_thread::get_id() << "] " << BUF(content); }
-#define ERR(content) { oneLog() << "ERR/" << std::this_thread::get_id() << "] " << BUF(content); }
+#define INF(content) { oneLog() << "INF/" << std::this_thread::get_id() << "] " << BUF(content) << std::flush; }
+#define WRN(content) { oneLog() << "WRN/" << std::this_thread::get_id() << "] " << BUF(content) << std::flush; }
+#define ERR(content) { oneLog() << "ERR/" << std::this_thread::get_id() << "] " << BUF(content) << std::flush; }
 
 // - HID() is to be more debug but product code shall disable them
 // - HID() uses cout since UniSmartLog is NOT MT safe
 //   . under single thread, can change cout back to oneLog() for smart log
 // - HID() is MT safe also upon UniSmartLog
 #if WITH_HID_LOG
 #define HID(content) { std::cout << "cout[" << rlib::mt_timestamp() << "/HID/" \
-    << std::this_thread::get_id() << "] " << BUF(content) << std::dec; }
+    << std::this_thread::get_id() << "] " << BUF(content) << std::dec << std::flush; }
 #else
 #define HID(content) {}
 #endif

src/log/UniSmartLog.hpp

@@ -73,7 +73,7 @@ class UniSmartLog
         auto&& name_log = name_log_S_.find(aUniLogName);
         return name_log == name_log_S_.end()
             ? 0
-            : static_cast<size_t>(name_log->second->tellp());  // avoid str().size() which creates string copy
+            : name_log->second->size();  // direct string size, no stream position query
     }
 #endif
 };