http: utility: Add base64encode

Add the base64encode() function to be used to encode binary data
to offload out of the BMC. Based on crow/utility.h, reworked for
readability.

Tested: Added unit test cases. Also verified data encoded with this
        function was the same as the original binary when using
        a decoder.

Change-Id: I0a27ffb0090c4613e296af33d11e2e2657957167
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/http/ut/utility_test.cpp b/http/ut/utility_test.cpp
index a81adf5..191a16a 100644
--- a/http/ut/utility_test.cpp
+++ b/http/ut/utility_test.cpp
@@ -16,3 +16,43 @@
     std::string result;
     EXPECT_FALSE(crow::utility::base64Decode(junkString, result));
 }
+
+TEST(Utility, Base64EncodeString)
+{
+    using namespace std::string_literals;
+    std::string encoded;
+
+    encoded = crow::utility::base64encode("");
+    EXPECT_EQ(encoded, "");
+
+    encoded = crow::utility::base64encode("f");
+    EXPECT_EQ(encoded, "Zg==");
+
+    encoded = crow::utility::base64encode("f0");
+    EXPECT_EQ(encoded, "ZjA=");
+
+    encoded = crow::utility::base64encode("f0\0"s);
+    EXPECT_EQ(encoded, "ZjAA");
+
+    encoded = crow::utility::base64encode("f0\0 "s);
+    EXPECT_EQ(encoded, "ZjAAIA==");
+
+    encoded = crow::utility::base64encode("f0\0 B"s);
+    EXPECT_EQ(encoded, "ZjAAIEI=");
+
+    encoded = crow::utility::base64encode("f0\0 Ba"s);
+    EXPECT_EQ(encoded, "ZjAAIEJh");
+
+    encoded = crow::utility::base64encode("f0\0 Bar"s);
+    EXPECT_EQ(encoded, "ZjAAIEJhcg==");
+}
+
+TEST(Utility, Base64EncodeDecodeString)
+{
+    using namespace std::string_literals;
+    std::string data("Data fr\0m 90 reading a \nFile"s);
+    std::string encoded = crow::utility::base64encode(data);
+    std::string decoded;
+    EXPECT_TRUE(crow::utility::base64Decode(encoded, decoded));
+    EXPECT_EQ(data, decoded);
+}