From e6e1978584d203f1f2f8587f178d879dfdf7fe06 Mon Sep 17 00:00:00 2001
From: Thomas Krijnen <t.krijnen@gmail.com>
Date: Sat, 6 Nov 2021 14:36:58 +0100
Subject: [PATCH] only call expensive wstring_convert() when necessary

---
 src/ifcparse/IfcCharacterDecoder.cpp | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/ifcparse/IfcCharacterDecoder.cpp b/src/ifcparse/IfcCharacterDecoder.cpp
index 8e93ae2437..456136a688 100644
--- a/src/ifcparse/IfcCharacterDecoder.cpp
+++ b/src/ifcparse/IfcCharacterDecoder.cpp
@@ -201,7 +201,18 @@ namespace {
 			builder_.push_back('\'');
 
 			if (mode == IfcParse::IfcCharacterDecoder::UTF8) {
-				return IfcUtil::convert_utf8(builder_);
+				if (builder_.empty()) {
+					static std::string empty;
+					return empty;
+				} else {
+					auto it = std::max_element(builder_.begin(), builder_.end());
+					if (*it <= 0x7e) {
+						std::string r(builder_.begin(), builder_.end());
+						return r;
+					} else {
+						return IfcUtil::convert_utf8(builder_);
+					}
+				}				
 			} else if (mode == IfcParse::IfcCharacterDecoder::SUBSTITUTE) {
 				std::string r;
 				r.reserve(builder_.size());