Add md5 testing to netplay

Allows to test current game, an arbitrary game or the sdcard of all players
at once.

Source/Core/Common/MD5.cpp

@@ -0,0 +1,52 @@
+// Copyright 2016 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <fstream>
+#include <functional>
+#include <mbedtls/md5.h>
+#include <string>
+
+#include "Common/MD5.h"
+#include "Common/StringUtil.h"
+#include "DiscIO/Blob.h"
+
+namespace MD5
+{
+std::string MD5Sum(const std::string& file_path, std::function<bool(int)> report_progress)
+{
+  std::string output_string;
+  std::vector<u8> data(8 * 1024 * 1024);
+  u64 read_offset = 0;
+  mbedtls_md5_context ctx;
+
+  std::unique_ptr<DiscIO::IBlobReader> file(DiscIO::CreateBlobReader(file_path));
+  u64 game_size = file->GetDataSize();
+
+  mbedtls_md5_starts(&ctx);
+
+  while (read_offset < game_size)
+  {
+    size_t read_size = std::min(static_cast<u64>(data.size()), game_size - read_offset);
+    if (!file->Read(read_offset, read_size, data.data()))
+      return output_string;
+
+    mbedtls_md5_update(&ctx, data.data(), read_size);
+    read_offset += read_size;
+
+    int progress =
+        static_cast<int>(static_cast<float>(read_offset) / static_cast<float>(game_size) * 100);
+    if (!report_progress(progress))
+      return output_string;
+  }
+
+  std::array<u8, 16> output;
+  mbedtls_md5_finish(&ctx, output.data());
+
+  // Convert to hex
+  for (u8 n : output)
+    output_string += StringFromFormat("%02x", n);
+
+  return output_string;
+}
+}