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///////////////////////////////////////////////////////////////////////////////
/// \file boyer_moore.hpp
/// Contains the boyer-moore implementation. Note: this is *not* a general-
/// purpose boyer-moore implementation. It truncates the search string at
/// 256 characters, but it is sufficient for the needs of xpressive.
//
// Copyright 2008 Eric Niebler. 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)
#ifndef BOOST_XPRESSIVE_DETAIL_BOYER_MOORE_HPP_EAN_10_04_2005
#define BOOST_XPRESSIVE_DETAIL_BOYER_MOORE_HPP_EAN_10_04_2005
// MS compatible compilers support #pragma once
#if defined(_MSC_VER)
# pragma once
# pragma warning(push)
# pragma warning(disable : 4100) // unreferenced formal parameter
# pragma warning(disable : 4996)
#endif
#include <climits> // for UCHAR_MAX
#include <cstddef> // for std::ptrdiff_t
#include <utility> // for std::max
#include <vector>
#include <boost/mpl/bool.hpp>
#include <boost/noncopyable.hpp>
#include <boost/iterator/iterator_traits.hpp>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/xpressive/detail/detail_fwd.hpp>
namespace boost { namespace xpressive { namespace detail
{
///////////////////////////////////////////////////////////////////////////////
// boyer_moore
//
template<typename BidiIter, typename Traits>
struct boyer_moore
: noncopyable
{
typedef typename iterator_value<BidiIter>::type char_type;
typedef Traits traits_type;
typedef has_fold_case<Traits> case_fold;
typedef typename Traits::string_type string_type;
// initialize the Boyer-Moore search data structure, using the
// search sub-sequence to prime the pump.
boyer_moore(char_type const *begin, char_type const *end, Traits const &tr, bool icase)
: begin_(begin)
, last_(begin)
, fold_()
, find_fun_(
icase
? (case_fold() ? &boyer_moore::find_nocase_fold_ : &boyer_moore::find_nocase_)
: &boyer_moore::find_
)
{
std::ptrdiff_t const uchar_max = UCHAR_MAX;
std::ptrdiff_t diff = std::distance(begin, end);
this->length_ = static_cast<unsigned char>((std::min)(diff, uchar_max));
std::fill_n(static_cast<unsigned char *>(this->offsets_), uchar_max + 1, this->length_);
--this->length_;
icase ? this->init_(tr, case_fold()) : this->init_(tr, mpl::false_());
}
BidiIter find(BidiIter begin, BidiIter end, Traits const &tr) const
{
return (this->*this->find_fun_)(begin, end, tr);
}
private:
void init_(Traits const &tr, mpl::false_)
{
for(unsigned char offset = this->length_; offset; --offset, ++this->last_)
{
this->offsets_[tr.hash(*this->last_)] = offset;
}
}
void init_(Traits const &tr, mpl::true_)
{
this->fold_.reserve(this->length_ + 1);
for(unsigned char offset = this->length_; offset; --offset, ++this->last_)
{
this->fold_.push_back(tr.fold_case(*this->last_));
for(typename string_type::const_iterator beg = this->fold_.back().begin(), end = this->fold_.back().end();
beg != end; ++beg)
{
this->offsets_[tr.hash(*beg)] = offset;
}
}
this->fold_.push_back(tr.fold_case(*this->last_));
}
// case-sensitive Boyer-Moore search
BidiIter find_(BidiIter begin, BidiIter end, Traits const &tr) const
{
typedef typename boost::iterator_difference<BidiIter>::type diff_type;
diff_type const endpos = std::distance(begin, end);
diff_type offset = static_cast<diff_type>(this->length_);
for(diff_type curpos = offset; curpos < endpos; curpos += offset)
{
std::advance(begin, offset);
char_type const *pat_tmp = this->last_;
BidiIter str_tmp = begin;
for(; tr.translate(*str_tmp) == *pat_tmp; --pat_tmp, --str_tmp)
{
if(pat_tmp == this->begin_)
{
return str_tmp;
}
}
offset = this->offsets_[tr.hash(tr.translate(*begin))];
}
return end;
}
// case-insensitive Boyer-Moore search
BidiIter find_nocase_(BidiIter begin, BidiIter end, Traits const &tr) const
{
typedef typename boost::iterator_difference<BidiIter>::type diff_type;
diff_type const endpos = std::distance(begin, end);
diff_type offset = static_cast<diff_type>(this->length_);
for(diff_type curpos = offset; curpos < endpos; curpos += offset)
{
std::advance(begin, offset);
char_type const *pat_tmp = this->last_;
BidiIter str_tmp = begin;
for(; tr.translate_nocase(*str_tmp) == *pat_tmp; --pat_tmp, --str_tmp)
{
if(pat_tmp == this->begin_)
{
return str_tmp;
}
}
offset = this->offsets_[tr.hash(tr.translate_nocase(*begin))];
}
return end;
}
// case-insensitive Boyer-Moore search with case-folding
BidiIter find_nocase_fold_(BidiIter begin, BidiIter end, Traits const &tr) const
{
typedef typename boost::iterator_difference<BidiIter>::type diff_type;
diff_type const endpos = std::distance(begin, end);
diff_type offset = static_cast<diff_type>(this->length_);
for(diff_type curpos = offset; curpos < endpos; curpos += offset)
{
std::advance(begin, offset);
string_type const *pat_tmp = &this->fold_.back();
BidiIter str_tmp = begin;
for(; pat_tmp->end() != std::find(pat_tmp->begin(), pat_tmp->end(), *str_tmp);
--pat_tmp, --str_tmp)
{
if(pat_tmp == &this->fold_.front())
{
return str_tmp;
}
}
offset = this->offsets_[tr.hash(*begin)];
}
return end;
}
private:
char_type const *begin_;
char_type const *last_;
std::vector<string_type> fold_;
BidiIter (boyer_moore::*const find_fun_)(BidiIter, BidiIter, Traits const &) const;
unsigned char length_;
unsigned char offsets_[UCHAR_MAX + 1];
};
}}} // namespace boost::xpressive::detail
#if defined(_MSC_VER)
# pragma warning(pop)
#endif
#endif
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