Imported gcc-4.4.3

[msp430-gcc.git] / libstdc++-v3 / testsuite / ext / pb_ds / example / store_hash.cc

diff --git a/libstdc++-v3/testsuite/ext/pb_ds/example/store_hash.cc b/libstdc++-v3/testsuite/ext/pb_ds/example/store_hash.cc
new file mode 100644 (file)
index 0000000..f762bfd
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/pb_ds/example/store_hash.cc
@@ -0,0 +1,97 @@
+// -*- C++ -*-
+
+// Copyright (C) 2005, 2006, 2009 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the terms
+// of the GNU General Public License as published by the Free Software
+// Foundation; either version 3, or (at your option) any later
+// version.
+
+// This library is distributed in the hope that it will be useful, but
+// WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+// General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+
+// Copyright (C) 2004 Ami Tavory and Vladimir Dreizin, IBM-HRL.
+
+// Permission to use, copy, modify, sell, and distribute this software
+// is hereby granted without fee, provided that the above copyright
+// notice appears in all copies, and that both that copyright notice
+// and this permission notice appear in supporting documentation. None
+// of the above authors, nor IBM Haifa Research Laboratories, make any
+// representation about the suitability of this software for any
+// purpose. It is provided "as is" without express or implied
+// warranty.
+
+/**
+ * @file store_hash_example.cpp
+ * An example showing how to store hash-values with
+ *     each entry in a hash-based container.
+ */
+
+/**
+ * This example shows how to configure a hash-based container to store
+ * the hash value of each key along with each entry. This technique
+ * is useful for complex keys (e.g., strings in this example), since
+ * it lowers the cost of collisions. For simpler types (e.g., integers),
+ * where the cost of comparing keys is of the same order as the cost
+ * of comparing hash values, this technique adds unnecessary overhead.
+ */
+
+#include <functional>
+#include <string>
+#include <ext/pb_ds/assoc_container.hpp>
+#include <ext/pb_ds/hash_policy.hpp>
+
+using namespace std;
+using namespace __gnu_pbds;
+
+// A string hash functor.
+struct string_hash : public unary_function<string, size_t>
+{
+  inline size_t
+  operator()(string str) const
+  {
+    string::const_iterator b = str.begin();
+    string::const_iterator e = str.end();
+
+    size_t hash = 0;
+    while (b != e)
+      {
+       hash *= 5;
+       hash += static_cast<size_t>(*b);
+       ++b;
+      }
+    return hash;
+  }
+};
+
+int main()
+{
+  // A collision-chaining hash table mapping strings to ints.
+  typedef
+    cc_hash_table<
+    string,
+    int,
+    string_hash,
+    equal_to<string>,
+    direct_mask_range_hashing<>,
+    hash_standard_resize_policy<>,
+    true>
+    map_t;
+
+  map_t h;
+
+  // Use regularly.
+  h["Hello, "] = 0;
+  h["world"] = 1;
+
+  return 0;
+}
+