From b72d7abfb05aab6e3be88d414811473cb9394465 Mon Sep 17 00:00:00 2001
From: Neil MacIntosh <neilmac@microsoft.com>
Date: Fri, 24 Jun 2016 04:54:09 -0700
Subject: [PATCH] Added definition of gsl::byte to match proposed std::byte.

---
 include/byte.h       | 46 ++++++++++++++++++++--
 tests/CMakeLists.txt |  1 +
 tests/byte_tests.cpp | 92 ++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 135 insertions(+), 4 deletions(-)
 create mode 100644 tests/byte_tests.cpp

diff --git a/include/byte.h b/include/byte.h
index c6449aa..6e32fef 100644
--- a/include/byte.h
+++ b/include/byte.h
@@ -23,10 +23,48 @@ namespace gsl
 {
     // This is a simple definition for now that allows
     // use of byte within span<> to be standards-compliant
-    //
-    // Ultimately a small language change would allow a more
-    // robust definition (see WG21 proposal P0257 for details).
-    using byte = unsigned char;
+    enum class byte : unsigned char {};
+
+    template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+    constexpr byte& operator<<=(byte& b, IntegerType shift) noexcept
+    { return b = byte(static_cast<unsigned char>(b) << shift); }
+
+    template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+    constexpr byte operator<<(byte b, IntegerType shift) noexcept
+    { return byte(static_cast<unsigned char>(b) << shift); }
+
+    template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+    constexpr byte& operator>>=(byte& b, IntegerType shift) noexcept
+    { return b = byte(static_cast<unsigned char>(b) >> shift); }
+
+    template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+    constexpr byte operator>> (byte b, IntegerType shift) noexcept
+    { return byte(static_cast<unsigned char>(b) >> shift); }
+
+    constexpr byte& operator|=(byte& l, byte r) noexcept
+    { return l = byte(static_cast<unsigned char>(l) | static_cast<unsigned char>(r)); }
+
+    constexpr byte operator|(byte l, byte r) noexcept
+    { return byte(static_cast<unsigned char>(l) + static_cast<unsigned char>(r)); }
+
+    constexpr byte& operator&=(byte& l, byte r) noexcept
+    { return l = byte(static_cast<unsigned char>(l) & static_cast<unsigned char>(r)); }
+
+    constexpr byte operator&(byte l, byte r) noexcept
+    { return byte(static_cast<unsigned char>(l) & static_cast<unsigned char>(r)); }
+
+    constexpr byte& operator^=(byte& l, byte r) noexcept
+    { return l = byte(static_cast<unsigned char>(l) ^ static_cast<unsigned char>(r)); }
+    
+    constexpr byte operator^(byte l, byte r) noexcept
+    { return byte(static_cast<unsigned char>(l) ^ static_cast<unsigned char>(r)); }
+    
+    constexpr byte operator~(byte b) noexcept
+    { return byte(~static_cast<unsigned char>(b)); }
+
+    template <class IntegerType, class = std::enable_if_t<std::is_integral<IntegerType>::value>>
+    constexpr IntegerType to_integer(byte b) noexcept { return {b}; }
+
     
 } // namespace gsl
 
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 9723309..009b52d 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -54,3 +54,4 @@ add_gsl_test(notnull_tests)
 add_gsl_test(assertion_tests)
 add_gsl_test(utils_tests)
 add_gsl_test(owner_tests)
+add_gsl_test(byte_tests)
\ No newline at end of file
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
new file mode 100644
index 0000000..ff91e50
--- /dev/null
+++ b/tests/byte_tests.cpp
@@ -0,0 +1,92 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Copyright (c) 2015 Microsoft Corporation. All rights reserved.
+//
+// This code is licensed under the MIT License (MIT).
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+// THE SOFTWARE.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include <UnitTest++/UnitTest++.h>
+#include <byte.h>
+
+#include <iostream>
+#include <list>
+#include <map>
+#include <memory>
+#include <string>
+#include <vector>
+
+using namespace std;
+using namespace gsl;
+
+namespace
+{
+
+SUITE(byte_tests)
+{
+    TEST(construction)
+    {
+        {
+            byte b = static_cast<byte>(4);
+            CHECK(static_cast<unsigned char>(b) == 4);
+        }
+
+        {
+            byte b = byte(12);
+            CHECK(static_cast<unsigned char>(b) == 12);
+        }
+
+        // waiting for C++17 enum class direct initializer support
+        //{
+        //    byte b { 14 };
+        //    CHECK(static_cast<unsigned char>(b) == 14);
+        //}
+    }
+
+    TEST(bitwise_operations)
+    {
+        byte b = byte(0xFF);
+
+        byte a = byte(0x00);
+        CHECK((b | a) == byte(0xFF));
+        CHECK(a == byte(0x00));
+
+        a |= b;
+        CHECK(a == byte(0xFF));
+
+        a = byte(0x01);
+        CHECK((b & a) == byte(0x01));
+
+        a &= b;
+        CHECK(a == byte(0x01));
+
+        CHECK((b ^ a) == byte(0xFE));
+        
+        CHECK(a == byte(0x01));
+        a ^= b;
+        CHECK(a == byte(0xFE));
+
+        a = byte(0x01);
+        CHECK(~a == byte(0xFE));
+
+        a = byte(0xFF);
+        CHECK((a << 4) == byte(0xF0));
+        CHECK((a >> 4) == byte(0x0F));
+
+        a <<= 4;
+        CHECK(a == byte(0xF0));
+        a >>= 4;
+        CHECK(a == byte(0x0F));
+    }
+}
+}
+
+int main(int, const char* []) { return UnitTest::RunAllTests(); }