Add error codes for signing error checks

include/jwt/impl/error_codes.ipp

@@ -0,0 +1,48 @@
+#ifndef CPP_JWT_ERROR_CODES_IPP
+#define CPP_JWT_ERROR_CODES_IPP
+
+namespace jwt {
+// Anonymous namespace
+namespace {
+
+/**
+ */
+struct AlgorithmErrCategory: std::error_category
+{
+  const char* name() const noexcept override
+  {
+    return "algorithms";
+  }
+
+  std::string message(int ev) const override
+  {
+    switch (static_cast<AlgorithmErrc>(ev))
+    {
+    case AlgorithmErrc::SigningErr:
+      return "signing failed";
+    case AlgorithmErrc::VerificationErr:
+      return "verification failed";
+    case AlgorithmErrc::NoneAlgorithmUsed:
+      return "none algorithm used";
+    };
+
+    assert (0 && "Code not reached");
+  }
+};
+
+// Create global object for the error categories
+const AlgorithmErrCategory theAlgorithmErrCategory {};
+
+}
+
+
+// Create the AlgorithmErrc error code
+std::error_code make_error_code(AlgorithmErrc err)
+{
+  return { static_cast<int>(err), theAlgorithmErrCategory };
+}
+
+
+} // END namespace jwt
+
+#endif