util: Make ToLower and ToUpper take a char

Unfortunately, `std::string` elements are (bare) chars. As these
are the most likely type to be passed to these functions, make them use
char instead of unsigned char. This avoids some casts.

2 files changed, 3 insertions, 3 deletions

diff --git a/src/util/strencodings.cpp b/src/util/strencodings.cpp
index 46146be66..fedeeac39 100644
--- a/src/util/strencodings.cpp
+++ b/src/util/strencodings.cpp
@@ -589,7 +589,7 @@ bool ParseHDKeypath(const std::string& keypath_str, std::vector<uint32_t>& keypa
 
 void Downcase(std::string& str)
 {
-    std::transform(str.begin(), str.end(), str.begin(), [](unsigned char c){return ToLower(c);});
+    std::transform(str.begin(), str.end(), str.begin(), [](char c){return ToLower(c);});
 }
 
 std::string Capitalize(std::string str)
diff --git a/src/util/strencodings.h b/src/util/strencodings.h
index e219e7df3..e392055f2 100644
--- a/src/util/strencodings.h
+++ b/src/util/strencodings.h
@@ -208,7 +208,7 @@ NODISCARD bool ParseHDKeypath(const std::string& keypath_str, std::vector<uint32
  * @return          the lowercase equivalent of c; or the argument
  *                  if no conversion is possible.
  */
-constexpr unsigned char ToLower(unsigned char c)
+constexpr char ToLower(char c)
 {
     return (c >= 'A' && c <= 'Z' ? (c - 'A') + 'a' : c);
 }
@@ -229,7 +229,7 @@ void Downcase(std::string& str);
  * @return          the uppercase equivalent of c; or the argument
  *                  if no conversion is possible.
  */
-constexpr unsigned char ToUpper(unsigned char c)
+constexpr char ToUpper(char c)
 {
     return (c >= 'a' && c <= 'z' ? (c - 'a') + 'A' : c);
 }