Add PKCS#7 padding implementation.

Chaos/Padding/PadPkcs7.hpp

@@ -0,0 +1,37 @@
+#ifndef CHAOS_PADDING_PADPKCS7_HPP
+#define CHAOS_PADDING_PADPKCS7_HPP
+
+#include <cstdint>
+#include <iterator>
+#include <limits>
+
+#include "Service/ChaosException.hpp"
+
+namespace Chaos::Padding
+{
+
+class PadPkcs7
+{
+public:
+    template<typename OutputIt>
+    static void Pad(OutputIt begin, OutputIt end)
+    {
+        auto dist = std::distance(begin, end);
+
+        if (dist >= 0 && dist <= std::numeric_limits<uint8_t>::max())
+        {
+            for (OutputIt it = begin; it != end; ++it)
+            {
+                *it = static_cast<uint8_t>(dist);
+            }
+        }
+        else
+        {
+            throw Service::ChaosException("PadPkcs7::Pad(): invalid range");
+        }
+    }
+};
+
+} // namespace Chaos::Padding
+
+#endif // CHAOS_PADDING_PADPKCS7_HPP