ProgressBar improvements (#305)

* changed ProgressBar so it doesn't use printf. printf by default is very slow on Windows due to weird buffering behaviour. During a 2 minute build download I profiled 35 CPU seconds inside printf
* changed so ProgressBar uses plain output mode if stdout is not a console/tty

3 files changed, 44 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 25af743fe..febd32eb4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -15,6 +15,8 @@
   - Improvement: Reduced I/O usage during upload and download
   - Improvement: Faster block regeneration when uploading in response to PutBuild/FinalizeBuild
   - Improvement: More trace scopes for build upload operations
+  - Improvement: Progress bar automatically switches to plain mode when stdout is not a console
+  - Improvement: Progress bar is much more efficient on Windows (switched away from printf)
   - Bugfix: Ensure that temporary folder for Jupiter downloads exists during verify phase
   - Bugfix: Fixed crash during download when trying to write outside a file range
   - Bugfix: MacOS / Linux zen build download now works correctly
diff --git a/src/zen/zen.cpp b/src/zen/zen.cpp
index 0fcf9d871..9d0eab7dc 100644
--- a/src/zen/zen.cpp
+++ b/src/zen/zen.cpp
@@ -32,6 +32,7 @@
 #include <zencore/scopeguard.h>
 #include <zencore/string.h>
 #include <zencore/trace.h>
+#include <zencore/windows.h>
 #include <zenhttp/httpcommon.h>
 #include <zenutil/logging.h>
 #include <zenutil/zenserverprocess.h>
@@ -56,6 +57,10 @@ ZEN_THIRD_PARTY_INCLUDES_END
 
 #include <zencore/memory/newdelete.h>
 
+#ifndef ZEN_PLATFORM_WINDOWS
+#	include <unistd.h>
+#endif
+
 //////////////////////////////////////////////////////////////////////////
 
 namespace zen {
@@ -261,8 +266,22 @@ ZenCmdBase::ResolveTargetHostSpec(const std::string& InHostSpec)
 	return ResolveTargetHostSpec(InHostSpec, /* out */ Dummy);
 }
 
+static bool
+IsStdoutTty()
+{
+#if ZEN_PLATFORM_WINDOWS
+	static HANDLE hStdOut	= ::GetStdHandle(STD_OUTPUT_HANDLE);
+	DWORD		  dwMode	= 0;
+	static bool	  IsConsole = ::GetConsoleMode(hStdOut, &dwMode);
+	return IsConsole;
+#else
+	return isatty(fileno(stdout));
+#endif
+}
+
 ProgressBar::ProgressBar(bool PlainProgress, bool ShowDetails)
-: m_PlainProgress(PlainProgress)
+: m_StdoutIsTty(IsStdoutTty())
+, m_PlainProgress(PlainProgress || !m_StdoutIsTty)
 , m_ShowDetails(ShowDetails)
 , m_LastUpdateMS(m_SW.GetElapsedTimeMs() - 10000)
 {
@@ -323,7 +342,27 @@ ProgressBar::UpdateState(const State& NewState, bool DoLinebreak)
 										 ETA,
 										 NewState.Details.empty() ? "" : fmt::format(". {}", NewState.Details));
 		std::string::size_type EraseLength = m_LastOutputLength > Output.length() ? (m_LastOutputLength - Output.length()) : 0;
-		printf("%s%s%s", Output.c_str(), std::string(EraseLength, ' ').c_str(), DoLinebreak ? "\n" : "");
+
+		ExtendableStringBuilder<128> LineToPrint;
+		LineToPrint << Output << std::string(EraseLength, ' ');
+		if (DoLinebreak)
+			LineToPrint << "\n";
+
+#if ZEN_PLATFORM_WINDOWS
+		static HANDLE hStdOut = GetStdHandle(STD_OUTPUT_HANDLE);
+
+		if (m_StdoutIsTty)
+		{
+			WriteConsoleA(hStdOut, LineToPrint.c_str(), (DWORD)LineToPrint.Size(), 0, 0);
+		}
+		else
+		{
+			::WriteFile(hStdOut, (LPCVOID)LineToPrint.c_str(), (DWORD)LineToPrint.Size(), 0, 0);
+		}
+#else
+		fwrite(LineToPrint.c_str(), 1, LineToPrint.Size(), stdout);
+#endif
+
 		m_LastOutputLength = DoLinebreak ? 0 : Output.length();
 		m_State			   = NewState;
 	}
diff --git a/src/zen/zen.h b/src/zen/zen.h
index 835c2b6ac..6765101db 100644
--- a/src/zen/zen.h
+++ b/src/zen/zen.h
@@ -94,6 +94,7 @@ public:
 	bool HasActiveTask() const;
 
 private:
+	const bool m_StdoutIsTty = true;
 	const bool m_PlainProgress;
 	const bool m_ShowDetails;
 	Stopwatch  m_SW;