Add requestId policy implementation (#239)

* Add requestId policy implementation
Includes uuid class

sdk/core/azure-core/inc/http/policy.hpp

@@ -8,6 +8,7 @@
 #include "http.hpp"
 #include "logging/logging.hpp"
 #include "transport.hpp"
+#include "uuid.hpp"
 
 #include <chrono>
 #include <utility>
@@ -106,6 +107,9 @@ namespace Azure { namespace Core { namespace Http {
   };
 
   class RequestIdPolicy : public HttpPolicy {
+  private:
+    constexpr static const char* RequestIdHeader = "x-ms-client-request-id";
+
   public:
     explicit RequestIdPolicy() {}
 
@@ -119,7 +123,9 @@ namespace Azure { namespace Core { namespace Http {
         Request& request,
         NextHttpPolicy nextHttpPolicy) const override
     {
-      // Do real work here
+      auto uuid = UUID::CreateUUID().GetUUIDString();
+
+      request.AddHeader(RequestIdHeader, uuid);
       return nextHttpPolicy.Send(ctx, request);
     }
   };

sdk/core/azure-core/inc/uuid.hpp

@@ -0,0 +1,82 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+#pragma once
+
+#include <new> // for placement new
+#include <random>
+#include <string>
+#include <utility> // for swap and move
+
+namespace Azure { namespace Core {
+
+  class UUID {
+
+  private:
+    static const int UUIDSize = 16;
+
+    uint8_t m_uuid[UUIDSize];
+    // The UUID reserved variants.
+    static constexpr uint8_t ReservedNCS = 0x80;
+    static constexpr uint8_t ReservedRFC4122 = 0x40;
+    static constexpr uint8_t ReservedMicrosoft = 0x20;
+    static constexpr uint8_t ReservedFuture = 0x00;
+
+  private:
+    UUID(uint8_t const uuid[UUIDSize])
+    {
+      memcpy(m_uuid, uuid, UUIDSize);
+    }
+
+  public:
+
+    std::string GetUUIDString()
+    {
+      // Guid is 36 characters
+      //  Add one byte for the \0
+      char s[37];
+
+      std::snprintf(
+          s,
+          sizeof(s),
+          "%2.2x%2.2x%2.2x%2.2x-%2.2x%2.2x-%2.2x%2.2x-%2.2x%2.2x-%2.2x%2.2x%2.2x%2.2x%2.2x%2.2x",
+          m_uuid[0],
+          m_uuid[1],
+          m_uuid[2],
+          m_uuid[3],
+          m_uuid[4],
+          m_uuid[5],
+          m_uuid[6],
+          m_uuid[7],
+          m_uuid[8],
+          m_uuid[9],
+          m_uuid[10],
+          m_uuid[11],
+          m_uuid[12],
+          m_uuid[13],
+          m_uuid[14],
+          m_uuid[15]);
+
+      return std::string(s);
+    }
+
+    static UUID CreateUUID() {
+      std::random_device rd;
+      std::mt19937 gen(rd());
+
+      uint8_t uuid[UUIDSize] = {};
+
+      for (int i = 0; i < UUIDSize; i += 4)
+        *reinterpret_cast<uint32_t*>(uuid + i) = gen();
+
+      // SetVariant to ReservedRFC4122
+      uuid[8] = (uuid[8] | ReservedRFC4122) & 0x7F;
+
+      constexpr uint8_t version = 4;
+
+      uuid[6] = (uuid[6] & 0xF) | (version << 4);
+
+      return UUID(uuid);
+    }
+  };
+}} // namespace Azure::Core

sdk/core/azure-core/test/uuid.cpp

@@ -0,0 +1,15 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+#include "gtest/gtest.h"
+#include <uuid.hpp>
+#include <string>
+#include <vector>
+
+using namespace Azure::Core;
+
+TEST(UUID, Basic)
+{
+  auto uuid = UUID::CreateUUID();
+  EXPECT_TRUE(uuid.GetUUIDString().length() == 36);
+}