adding base64 encoding

lib/bytes/include/bytes/bytes.h

@@ -115,4 +115,10 @@ to_hex(const bytes& data);
 bytes
 from_hex(const std::string& hex);
 
+std::string
+to_base64(const bytes& data);
+
+std::string
+to_base64url(const bytes& data);
+
 } // namespace bytes_ns

lib/bytes/src/bytes.cpp

@@ -4,6 +4,8 @@
 #include <iostream>
 #include <sstream>
 #include <stdexcept>
+#include <openssl/evp.h>
+#include <openssl/bio.h>
 
 namespace bytes_ns {
 
@@ -137,4 +139,67 @@ operator!=(const std::vector<uint8_t>& lhs, const bytes_ns::bytes& rhs)
   return rhs != lhs;
 }
 
+std::string
+to_base64(const bytes& data)
+{
+  bool done = false;
+  int result = 0;
+
+  if (data.empty()) {
+    return "";
+  }
+
+  BIO* b64 = BIO_new(BIO_f_base64());
+  BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
+  BIO* out = BIO_new(BIO_s_mem());
+  BIO_push(b64, out);
+
+  while (!done) {
+    result = BIO_write(b64, data.data(), static_cast<int>(data.size()));
+
+    if (result <= 0) {
+      if (BIO_should_retry(b64)) {
+        continue;
+      }
+      throw std::runtime_error("base64 encode failed");
+    }
+    done = true;
+  }
+  BIO_flush(b64);
+  char* string_ptr = nullptr;
+  // long string_len = BIO_get_mem_data(out, &string_ptr);
+  // BIO_get_mem_data failed clang-tidy
+  long string_len = BIO_ctrl(out, BIO_CTRL_INFO, 0, &string_ptr);
+  auto return_value = std::string(string_ptr, string_len);
+
+  BIO_set_close(out, BIO_NOCLOSE);
+  BIO_free(b64);
+  BIO_free(out);
+  return return_value;
+}
+
+std::string
+to_base64url(const bytes& data)
+{
+  if (data.empty()) {
+    return "";
+  }
+
+  std::string return_value = to_base64(data);
+
+  // remove the end padding
+  auto sz = return_value.find_first_of('=');
+
+  if (sz != std::string::npos) {
+    return_value = return_value.substr(0, sz);
+  }
+
+  // replace plus with hyphen
+  std::replace(return_value.begin(), return_value.end(), '+', '-');
+
+  // replace slash with underscore
+  std::replace(return_value.begin(), return_value.end(), '/', '_');
+  return return_value;
+}
+
 } // namespace bytes_ns

lib/bytes/test/bytes.cpp

@@ -2,6 +2,7 @@
 #include <doctest/doctest.h>
 #include <memory>
 #include <sstream>
+#include <vector>
 
 using namespace bytes_ns;
 using namespace std::literals::string_literals;
@@ -40,6 +41,31 @@ TEST_CASE("To/from hex/ASCII")
   REQUIRE(from_ascii(str) == ascii);
 }
 
+TEST_CASE("To Base64 / To Base64Url")
+{
+  struct KnownAnswerTest
+  {
+    bytes data;
+    std::string base64;
+    std::string base64u;
+  };
+
+  const std::vector<KnownAnswerTest> cases{
+    { from_ascii("hello there"), "aGVsbG8gdGhlcmU=", "aGVsbG8gdGhlcmU" },
+    { from_ascii("A B C D E F "), "QSBCIEMgRCBFIEYg", "QSBCIEMgRCBFIEYg" },
+    { from_ascii("hello\xfethere"), "aGVsbG/+dGhlcmU=", "aGVsbG_-dGhlcmU" },
+    { from_ascii("\xfe"), "/g==", "_g" },
+    { from_ascii("\x01\x02"), "AQI=", "AQI" },
+    { from_ascii("\x01"), "AQ==", "AQ" },
+    { from_ascii(""), "", "" },
+  };
+
+  for (const auto& tc : cases) {
+    REQUIRE(to_base64(tc.data) == tc.base64);
+    REQUIRE(to_base64url(tc.data) == tc.base64u);
+  }
+}
+
 TEST_CASE("Operators")
 {
   const auto lhs = from_hex("00010203");