1 files changed, 80 insertions, 0 deletions
diff --git a/ml/dlib/dlib/general_hash/general_hash.h b/ml/dlib/dlib/general_hash/general_hash.h
new file mode 100644
index 000000000..3de0b2698
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+++ b/ml/dlib/dlib/general_hash/general_hash.h
@@ -0,0 +1,80 @@
+// Copyright (C) 2003  Davis E. King (davis@dlib.net)
+// License: Boost Software License   See LICENSE.txt for the full license.
+#ifndef DLIB_GENERAL_HASh_
+#define DLIB_GENERAL_HASh_
+
+
+#include <string>
+#include "hash.h"
+
+namespace dlib 
+{
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------- provide a general hashing function object ----------------------
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+    template <
+        typename T
+        >
+    class general_hash
+    {
+    public:
+        inline unsigned long operator() (
+            const T& item
+        ) const;
+    };
+    /*!
+        Note that the default behavior of general hash is to attempt to cast
+        an object of type T to an unsigned long and use that as the hash.
+
+        REQUIREMENTS ON general_hash
+            - must have a default constructor
+            - must be a function object which overloads operator() as follows:
+              unsigned long operator()(const T& item)             
+            - must take item, compute a hash number and return it 
+            - must not throw
+            - must define the hash in such a way that all equivalent objects have 
+              the same hash.  where equivalent means the following:
+                  definition of equivalent:
+                  a is equivalent to b if
+                  a < b == false and
+                  b < a == false
+    !*/
+
+// ---------------
+
+    template <
+        typename T
+        >
+    unsigned long general_hash<T>:: 
+    operator() (
+        const T& item
+    ) const
+    {
+        // hash any types that have a conversion to uint64 
+        return hash(static_cast<uint64>(item));
+    }
+
+
+// ---------------
+
+    // std::string hash
+    template <>
+    inline unsigned long general_hash<std::string>:: 
+    operator() (
+        const std::string& item
+    ) const
+    {
+        return hash(item);
+    }
+
+// ----------------------------------------------------------------------------------------
+// ----------------------------------------------------------------------------------------
+
+}
+
+#endif // DLIB_GENERAL_HASh_
+