Implement boost hash for string_view

.travis.yml

@@ -192,6 +192,7 @@ install:
   - git submodule update --init libs/static_assert
   - git submodule update --init libs/throw_exception
   - git submodule update --init libs/type_traits
+  - git submodule update --init libs/container_hash
   - cp -r $TRAVIS_BUILD_DIR/* libs/utility
   - ./bootstrap.sh
   - ./b2 headers

appveyor.yml

@@ -36,6 +36,7 @@ install:
   - git submodule update --init libs/static_assert
   - git submodule update --init libs/throw_exception
   - git submodule update --init libs/type_traits
+  - git submodule update --init libs/container_hash
   - xcopy /s /e /q %APPVEYOR_BUILD_FOLDER% libs\utility
   - cmd /c bootstrap
   - b2 -d0 headers

include/boost/utility/string_view.hpp

@@ -21,6 +21,7 @@
 #include <boost/detail/workaround.hpp>
 #include <boost/utility/string_view_fwd.hpp>
 #include <boost/throw_exception.hpp>
+#include <boost/container_hash/hash.hpp>
 
 #include <cstddef>
 #include <stdexcept>
@@ -690,6 +691,10 @@ namespace boost {
         }
 #endif
 
+    template <class charT, class traits>
+    std::size_t hash_value(basic_string_view<charT, traits> s) {
+        return boost::hash_range(s.begin(), s.end());
+        }
 }
 
 #if 0

test/string_view_test1.cpp

@@ -85,6 +85,14 @@ void test_remove ( const std::string &str ) {
       }
     }
 
+void test_hash(const std::string& str) {
+    string_view ref = str;
+    BOOST_TEST(boost::hash_value(ref) == boost::hash_value(str));
+    boost::hash<std::string> hstr;
+    boost::hash<string_view> hsv;
+    BOOST_TEST(hsv(ref) == hstr(str));
+    }
+
 const char *test_strings [] = {
     "",
     "1",
@@ -102,6 +110,7 @@ int main()
         test_substr ( *p );
         test_remove ( *p );
         null_tests ( *p );
+        test_hash( *p );
 
         p++;
         }