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diff --git a/base/bitfield.hh b/base/bitfield.hh
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+/*
+ * Copyright (c) 2003 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __BITFIELD_HH
+#define __BITFIELD_HH
+
+#include <inttypes.h>
+
+/**
+ * Generate a 64-bit mask of 'nbits' 1s, right justified.
+ */
+inline uint64_t
+mask(int nbits)
+{
+    return (nbits == 64) ? (uint64_t)-1LL : (1ULL << nbits) - 1;
+}
+
+
+/**
+ * Extract the bitfield from position 'first' to 'last' (inclusive)
+ * from 'val' and right justify it.  MSB is numbered 63, LSB is 0.
+ */
+template <class T>
+inline
+T
+bits(T val, int first, int last)
+{
+    int nbits = first - last + 1;
+    return (val >> last) & mask(nbits);
+}
+
+/**
+ * Sign-extend an N-bit value to 64 bits.
+ */
+template <int N>
+inline
+int64_t
+sext(uint64_t val)
+{
+    int sign_bit = bits(val, N-1, N-1);
+    return sign_bit ? (val | ~mask(N)) : val;
+}
+
+#endif