base64decode should return immediately if the input is empty

src/futils.cpp

@@ -90,7 +90,7 @@ static char to_hex(char code) {
 
 /// @brief Convert a hex character to its integer value.
 static char from_hex(char ch) {
-  return isdigit(ch) ? ch - '0' : static_cast<char>(tolower(ch)) - 'a' + 10;
+  return 0xF & (isdigit(ch) ? ch - '0' : static_cast<char>(tolower(ch)) - 'a' + 10);
 }
 
 std::string urlencode(const std::string& str) {
@@ -168,7 +168,7 @@ int base64encode(const void* data_buf, size_t dataLength, char* result, size_t r
 size_t base64decode(const char* in, char* out, size_t out_size) {
   size_t result = 0;
   size_t input_length = in ? ::strlen(in) : 0;
-  if (!in || input_length % 4 != 0)
+  if (!in || input_length % 4 != 0 || input_length == 0)
     return result;
 
   auto encoding_table = reinterpret_cast<const unsigned char*>(base64_encode);