Subject: [Boost-commit] svn:boost r62923 - sandbox/SOC/2010/bits_and_ints/boost/integer
From: muriloufg_at_[hidden]
Date: 2010-06-13 18:53:43
Author: murilov
Date: 2010-06-13 18:53:41 EDT (Sun, 13 Jun 2010)
New Revision: 62923
URL: http://svn.boost.org/trac/boost/changeset/62923
Log:
Started working with interleave functions.
Added:
sandbox/SOC/2010/bits_and_ints/boost/integer/interleave.hpp (contents, props changed)
Added: sandbox/SOC/2010/bits_and_ints/boost/integer/interleave.hpp
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--- (empty file)
+++ sandbox/SOC/2010/bits_and_ints/boost/integer/interleave.hpp 2010-06-13 18:53:41 EDT (Sun, 13 Jun 2010)
@@ -0,0 +1,69 @@
+// Boost integer/interleave.hpp header file ------------------------------//
+
+// (C) Copyright Murilo Adriano Vasconcelos 2010.
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt
+
+// See http://www.boost.org for updates, documentation, and revision history.
+
+#ifndef BOOST_INTERLEAVE_INCLUDED
+#define BOOST_INTERLEAVE_INCLUDED
+
+#include <boost/utility/enable_if.hpp>
+#include <boost/type_traits/is_integral.hpp>
+
+/*
+ * Bit interleaving functions.
+ *
+ * Interleave the bits of two integers in one integer.
+ * For example:
+ * a = 5; // 0000 0101
+ * b = 10; // 0000 1010
+ * z = interleave(a, b); // z = 102
+ *
+ * a = 0 0 0 0 0 1 0 1
+ * b = 0 0 0 0 1 0 1 0
+ * z = 0000000001100110
+ */
+
+namespace boost
+{
+
+template <typename T>
+inline typename enable_if_c<is_integral<T>::type::value && sizeof(T) == 4, T>::type
+interleave(T x, T y)
+{
+ // puts the byte 2 in the byte 4
+ // and the byte 3 in the byte 5
+ a = (a | (a << 8)) & 0x00FF00FF;
+
+ // puts the bytes in alternate
+ // bytes
+ a = (a | (a << 4)) & 0x0F0F0F0F;
+
+ // now the original bits are in
+ // the lowest 2 bits of the nibbles
+ a = (a | (a << 2)) & 0x33333333;
+
+ // now the original bits are in
+ // the even bits
+ a = (a | (a << 1)) & 0x55555555;
+
+ // do the same with b
+ b = (b | (b << 8)) & 0x00FF00FF;
+ b = (b | (b << 4)) & 0x0F0F0F0F;
+ b = (b | (b << 2)) & 0x33333333;
+ b = (b | (b << 1)) & 0x55555555;
+ // now the original bits are in
+ // the odd bits
+ b <<= 1;
+
+ // the result is the union of
+ // a and b bits
+ return (a | b);
+}
+
+}
+
+#endif
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