Implements custom tolower and toupper functions.

This commit implements custom equivalents for the C and C++ `tolower` and `toupper` Standard Library functions.
In addition it implements a utility function to capitalize the first letter of a string.

1 files changed, 44 insertions, 0 deletions

diff --git a/src/utilstrencodings.h b/src/utilstrencodings.h
index 8f29f8f322..846a3917a2 100644
--- a/src/utilstrencodings.h
+++ b/src/utilstrencodings.h
@@ -186,4 +186,48 @@ bool ConvertBits(const O& outfn, I it, I end) {
 /** Parse an HD keypaths like "m/7/0'/2000". */
 bool ParseHDKeypath(const std::string& keypath_str, std::vector<uint32_t>& keypath);
 
+/**
+ * Converts the given character to its lowercase equivalent.
+ * This function is locale independent. It only converts uppercase
+ * characters in the standard 7-bit ASCII range.
+ * @param[in] c     the character to convert to lowercase.
+ * @return          the lowercase equivalent of c; or the argument
+ *                  if no conversion is possible.
+ */
+constexpr unsigned char ToLower(unsigned char c)
+{
+    return (c >= 'A' && c <= 'Z' ? (c - 'A') + 'a' : c);
+}
+
+/**
+ * Converts the given string to its lowercase equivalent.
+ * This function is locale independent. It only converts uppercase
+ * characters in the standard 7-bit ASCII range.
+ * @param[in,out] str   the string to convert to lowercase.
+ */
+void Downcase(std::string& str);
+
+/**
+ * Converts the given character to its uppercase equivalent.
+ * This function is locale independent. It only converts lowercase
+ * characters in the standard 7-bit ASCII range.
+ * @param[in] c     the character to convert to uppercase.
+ * @return          the uppercase equivalent of c; or the argument
+ *                  if no conversion is possible.
+ */
+constexpr unsigned char ToUpper(unsigned char c)
+{
+    return (c >= 'a' && c <= 'z' ? (c - 'a') + 'A' : c);
+}
+
+/**
+ * Capitalizes the first character of the given string.
+ * This function is locale independent. It only capitalizes the
+ * first character of the argument if it has an uppercase equivalent
+ * in the standard 7-bit ASCII range.
+ * @param[in] str   the string to capitalize.
+ * @return          string with the first letter capitalized.
+ */
+std::string Capitalize(std::string str);
+
 #endif // BITCOIN_UTILSTRENCODINGS_H