From 942a2c3f689b46107538d49a67dbf74c76e672b8 Mon Sep 17 00:00:00 2001
From: m-holger <m-holger@kubitscheck.org>
Date: Wed, 4 Jan 2023 11:17:01 +0000
Subject: [PATCH] Add new function QUtil::hex_encode_char

---
 include/qpdf/QUtil.hh | 13 +++++++++++++
 libqpdf/QPDF_Name.cc  |  2 +-
 2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/qpdf/QUtil.hh b/include/qpdf/QUtil.hh
index 6d9d18ae..27521a70 100644
--- a/include/qpdf/QUtil.hh
+++ b/include/qpdf/QUtil.hh
@@ -210,6 +210,11 @@ namespace QUtil
     QPDF_DLL
     std::string hex_encode(std::string const&);
 
+    // Returns lower-case hex-encoded version of the char including a leading
+    // "#".
+    QPDF_DLL
+    inline std::string hex_encode_char(char);
+
     // Returns a string that is the result of decoding the input
     // string. The input string may consist of mixed case hexadecimal
     // digits. Any characters that are not hexadecimal digits will be
@@ -583,4 +588,12 @@ QUtil::is_number(char const* p)
     return found_digit;
 }
 
+inline std::string
+QUtil::hex_encode_char(char c)
+{
+    static auto constexpr hexchars = "0123456789abcdef";
+    return {
+        '#', hexchars[static_cast<unsigned char>(c) >> 4], hexchars[c & 0x0f]};
+}
+
 #endif // QUTIL_HH
diff --git a/libqpdf/QPDF_Name.cc b/libqpdf/QPDF_Name.cc
index 353cf311..1587bcf4 100644
--- a/libqpdf/QPDF_Name.cc
+++ b/libqpdf/QPDF_Name.cc
@@ -38,7 +38,7 @@ QPDF_Name::normalizeName(std::string const& name)
             // invalid #.
             result += "#";
         } else if (strchr("#()<>[]{}/%", ch) || (ch < 33) || (ch > 126)) {
-            result += "#" + QUtil::hex_encode(std::string(&ch, 1));
+            result += QUtil::hex_encode_char(ch);
         } else {
             result += ch;
         }