[Boost-commit] svn:boost r62923 - sandbox/SOC/2010/bits_and_ints/boost/integer

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
==============================================================================
--- (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
\ No newline at end of file