Subject: [Boost-commit] svn:boost r75993 - trunk/boost
From: dwalker07_at_[hidden]
Date: 2011-12-16 10:32:28
Author: dlwalker
Date: 2011-12-16 10:32:27 EST (Fri, 16 Dec 2011)
New Revision: 75993
URL: http://svn.boost.org/trac/boost/changeset/75993
Log:
Changed reflection routines from a function-containing class template to a bunch of functions and function templates.
Text files modified:
trunk/boost/crc.hpp | 74 +++++++++++++++++++++++----------------
1 files changed, 43 insertions(+), 31 deletions(-)
Modified: trunk/boost/crc.hpp
==============================================================================
--- trunk/boost/crc.hpp (original)
+++ trunk/boost/crc.hpp 2011-12-16 10:32:27 EST (Fri, 16 Dec 2011)
@@ -9,6 +9,7 @@
#ifndef BOOST_CRC_HPP
#define BOOST_CRC_HPP
+#include <boost/array.hpp> // for boost::array
#include <boost/config.hpp> // for BOOST_STATIC_CONSTANT, etc.
#include <boost/cstdint.hpp> // for UINTMAX_C
#include <boost/integer.hpp> // for boost::uint_t
@@ -253,38 +254,50 @@
UINTMAX_C( 1 )) : 0u )>
{};
-
- // Reflection routine class wrapper
- // (since MS VC++ 6 couldn't handle the unwrapped version)
- template < std::size_t Bits >
- struct reflector
+ // Bit-reflection functions (BitSize is the number of low bits to reflect.)
+ template < int BitSize, typename Unsigned >
+ Unsigned reflect_unsigned_partially( Unsigned x )
{
- typedef typename boost::uint_t<Bits>::fast value_type;
+ for ( Unsigned l = 1u, h = l << (BitSize - 1) ; h > l ; h >>= 1, l <<=
+ 1 )
+ {
+ Unsigned const m = h | l, t = x & m;
- static value_type reflect( value_type x );
+ if ( (t == h) || (t == l) )
+ x ^= m;
+ }
- }; // boost::detail::reflector
+ return x;
+ }
- // Function that reflects its argument
- template < std::size_t Bits >
- typename reflector<Bits>::value_type
- reflector<Bits>::reflect
- (
- typename reflector<Bits>::value_type x
- )
+ template < typename Unsigned >
+ Unsigned reflect_unsigned_fully( Unsigned x )
{
- value_type reflection = 0;
- value_type const one = 1;
+ return reflect_unsigned_partially<
+ std::numeric_limits<Unsigned>::digits, Unsigned >( x );
+ }
- for ( std::size_t i = 0 ; i < Bits ; ++i, x >>= 1 )
- {
- if ( x & one )
- {
- reflection |= ( one << (Bits - 1u - i) );
- }
- }
+ unsigned char reflect_byte_slowly( unsigned char x )
+ { return reflect_unsigned_fully( x ); }
+
+ boost::array< unsigned char, (UINTMAX_C( 1 ) << CHAR_BIT) >
+ make_byte_reflection_table()
+ {
+ boost::array<unsigned char, ( UINTMAX_C(1) << CHAR_BIT )> result;
+
+ for ( boost::uint_t<CHAR_BIT + 1>::fast i = 0u ; i <=
+ UCHAR_MAX ; ++i )
+ result[ i ] = reflect_byte_slowly( i );
+
+ return result;
+ }
+
+ unsigned char reflect_byte( unsigned char x )
+ {
+ static boost::array<unsigned char, ( UINTMAX_C(1) << CHAR_BIT )> const
+ table = make_byte_reflection_table();
- return reflection;
+ return table[ x ];
}
@@ -406,7 +419,7 @@
#ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
// Possibly reflect a remainder
static value_type reflect( value_type x )
- { return detail::reflector<Bits>::reflect( x ); }
+ { return reflect_unsigned_partially<Bits>(x); }
// Compare a byte to the remainder's highest byte
static unsigned char index( value_type rem, unsigned char x )
@@ -418,7 +431,7 @@
#else
// Possibly reflect a remainder
static value_type reflect( value_type x )
- { return DoReflect ? detail::reflector<Bits>::reflect( x ) : x; }
+ { return DoReflect ? reflect_unsigned_partially<Bits>(x) : x; }
// Compare a byte to the remainder's highest byte
static unsigned char index( value_type rem, unsigned char x )
@@ -612,8 +625,7 @@
unsigned char byte
)
{
- process_bits( (rft_in_ ? detail::reflector<CHAR_BIT>::reflect(byte)
- : byte), CHAR_BIT );
+ process_bits( (rft_in_ ? detail::reflect_byte( byte ) : byte), CHAR_BIT );
}
template < std::size_t Bits >
@@ -653,8 +665,8 @@
(
) const
{
- return ( (rft_out_ ? detail::reflector<Bits>::reflect( rem_ ) : rem_)
- ^ final_ ) & detail::low_bits_mask_c<Bits>::value;
+ return ( (rft_out_ ? detail::reflect_unsigned_partially<Bits>( rem_ ) :
+ rem_) ^ final_ ) & detail::low_bits_mask_c<Bits>::value;
}