From 09bd1fafb131020a81e6519f65e9ba58d7a09abd Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Tue, 27 Oct 2020 11:42:09 -0400
Subject: Improve efficiency of number to string conversion

---
 libqpdf/QUtil.cc | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

(limited to 'libqpdf')

diff --git a/libqpdf/QUtil.cc b/libqpdf/QUtil.cc
index 366365f1..5442b5ff 100644
--- a/libqpdf/QUtil.cc
+++ b/libqpdf/QUtil.cc
@@ -267,16 +267,26 @@ int_to_string_base_internal(T num, int base, int length)
         throw std::logic_error(
             "int_to_string_base called with unsupported base");
     }
-    std::ostringstream buf;
-    buf.imbue(std::locale::classic());
-    buf << std::setbase(base) << std::nouppercase << num;
+    std::string cvt;
+    if (base == 10)
+    {
+        // Use the more efficient std::to_string when possible
+        cvt = std::to_string(num);
+    }
+    else
+    {
+        std::ostringstream buf;
+        buf.imbue(std::locale::classic());
+        buf << std::setbase(base) << std::nouppercase << num;
+        cvt = buf.str();
+    }
     std::string result;
-    int str_length = QIntC::to_int(buf.str().length());
+    int str_length = QIntC::to_int(cvt.length());
     if ((length > 0) && (str_length < length))
     {
 	result.append(QIntC::to_size(length - str_length), '0');
     }
-    result += buf.str();
+    result += cvt;
     if ((length < 0) && (str_length < -length))
     {
 	result.append(QIntC::to_size(-length - str_length), ' ');
-- 
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