Added to_byte method for issue #329

I have added the to_byte method and updated the unit tests.

This gives slightly nicer syntax than static_cast, is better than the
c-style cast used in the unit test.

See: https://github.com/Microsoft/GSL/issues/329#issuecomment-240588515

2 files changed, 29 insertions, 18 deletions

diff --git a/gsl/gsl_byte b/gsl/gsl_byte
index 91ce9d2..98749a7 100644
--- a/gsl/gsl_byte
+++ b/gsl/gsl_byte
@@ -106,6 +106,12 @@ constexpr IntegerType to_integer(byte b) noexcept
     return {b};
 }
 
+constexpr byte to_byte(unsigned char i) noexcept
+{
+    return static_cast<byte>(i);
+}
+
+
 } // namespace gsl
 
 #ifdef _MSC_VER
diff --git a/tests/byte_tests.cpp b/tests/byte_tests.cpp
index f2f8026..d6d4823 100644
--- a/tests/byte_tests.cpp
+++ b/tests/byte_tests.cpp
@@ -43,6 +43,11 @@ SUITE(byte_tests)
             byte b = byte(12);
             CHECK(static_cast<unsigned char>(b) == 12);
         }
+        
+        {
+            byte b = to_byte(12);
+            CHECK(static_cast<unsigned char>(b) == 12);
+        }
 
         // waiting for C++17 enum class direct initializer support
         //{
@@ -53,38 +58,38 @@ SUITE(byte_tests)
 
     TEST(bitwise_operations)
     {
-        byte b = byte(0xFF);
+        byte b = to_byte(0xFF);
 
-        byte a = byte(0x00);
-        CHECK((b | a) == byte(0xFF));
-        CHECK(a == byte(0x00));
+        byte a = to_byte(0x00);
+        CHECK((b | a) == to_byte(0xFF));
+        CHECK(a == to_byte(0x00));
 
         a |= b;
-        CHECK(a == byte(0xFF));
+        CHECK(a == to_byte(0xFF));
 
-        a = byte(0x01);
-        CHECK((b & a) == byte(0x01));
+        a = to_byte(0x01);
+        CHECK((b & a) == to_byte(0x01));
 
         a &= b;
-        CHECK(a == byte(0x01));
+        CHECK(a == to_byte(0x01));
 
-        CHECK((b ^ a) == byte(0xFE));
+        CHECK((b ^ a) == to_byte(0xFE));
         
-        CHECK(a == byte(0x01));
+        CHECK(a == to_byte(0x01));
         a ^= b;
-        CHECK(a == byte(0xFE));
+        CHECK(a == to_byte(0xFE));
 
-        a = byte(0x01);
-        CHECK(~a == byte(0xFE));
+        a = to_byte(0x01);
+        CHECK(~a == to_byte(0xFE));
 
-        a = byte(0xFF);
-        CHECK((a << 4) == byte(0xF0));
-        CHECK((a >> 4) == byte(0x0F));
+        a = to_byte(0xFF);
+        CHECK((a << 4) == to_byte(0xF0));
+        CHECK((a >> 4) == to_byte(0x0F));
 
         a <<= 4;
-        CHECK(a == byte(0xF0));
+        CHECK(a == to_byte(0xF0));
         a >>= 4;
-        CHECK(a == byte(0x0F));
+        CHECK(a == to_byte(0x0F));
     }
 }