ascii: add UDL for vector and array conversions

ascii.hpp

@@ -11,11 +11,11 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  *
- * Copyright 2016 Danny Robson <danny@nerdcruft.net>
+ * Copyright 2016-2018 Danny Robson <danny@nerdcruft.net>
  */
 
-#ifndef __CRUFT_UTIL_ASCII_HPP
-#define __CRUFT_UTIL_ASCII_HPP
+#ifndef CRUFT_UTIL_ASCII_HPP
+#define CRUFT_UTIL_ASCII_HPP
 
 #include "annotation.hpp"
 
@@ -125,4 +125,40 @@ namespace util::ascii {
     }
 }
 
+
+///////////////////////////////////////////////////////////////////////////////
+#include "debug.hpp"
+#include <vector>
+
+/// convert an ascii string of hex digits into a vector of uint8
+std::vector<std::uint8_t>
+inline
+operator"" _hex2u8 (const char *str, size_t len)
+{
+    CHECK_MOD (len, 2);
+    std::vector<uint8_t> res (len/2);
+
+    for (size_t i = 0; i < len; i += 2)
+        res[i/2] = util::ascii::from_hex (str[i]) << 4 | util::ascii::from_hex (str[i+1]);
+    return res;
+};
+
+
+///////////////////////////////////////////////////////////////////////////////
+template <typename CharT, CharT ...StrV>
+constexpr auto
+operator"" _hex2array (void)
+{
+    static_assert (sizeof ...(StrV) % 2 == 0);
+
+    std::array<std::uint8_t,sizeof...(StrV)/2> res {};
+    constexpr CharT literal[] = { StrV... };
+
+    for (size_t i = 0; i < res.size (); ++i)
+        res[i] = util::ascii::from_hex (literal[i*2+0]) << 4 |
+                 util::ascii::from_hex (literal[i*2+1]);
+
+    return res;
+}
+
 #endif

test/ascii.cpp

@@ -75,5 +75,8 @@ main (int, char**)
         );
     }
 
+    tap.expect_eq ("6a"_hex2u8, std::vector<uint8_t>({0x6a}), "hex2u8, 1 byte");
+    tap.expect_eq ("a6"_hex2array, std::array<uint8_t,1> ({0xa6}), "hex2array, 1 byte");
+
     return tap.status ();
 }