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// file : butl/prefix-map -*- C++ -*-
// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
// license : MIT; see accompanying LICENSE file
#ifndef BUTL_PREFIX_MAP
#define BUTL_PREFIX_MAP
#include <map>
#include <string>
#include <utility> // move
#include <algorithm> // min
namespace butl
{
// A map of hierarchical "paths", e.g., 'foo.bar' or 'foo/bar' with
// the ability to retrieve a range of entries that have a specific
// prefix. The '.' and '/' above are the delimiter characters.
//
// Note that as a special rule, the default implementation of
// compare_prefix treats empty key as everyone's prefix even if
// the paths don't start with the delimiter (useful to represent
// a "root path").
//
// Implementation-wise, the idea is to pretend that each key ends
// with the delimiter. This way we automatically avoid matching
// 'foobar' as having a prefix 'foo'.
//
template <typename K>
struct compare_prefix;
template <typename C>
struct compare_prefix<std::basic_string<C>>
{
typedef std::basic_string<C> K;
typedef C delimiter_type;
typedef typename K::size_type size_type;
typedef typename K::traits_type traits_type;
explicit
compare_prefix (delimiter_type d): d_ (d) {}
bool
operator() (const K& x, const K& y) const
{
return compare (x.c_str (), x.size (), y.c_str (), y.size ()) < 0;
}
// Note: doesn't check for k.size () being at least p.size ().
//
bool
prefix (const K& p, const K& k) const
{
size_type pn (p.size ());
return pn == 0 || // Empty key is always a prefix.
compare (
p.c_str (), pn, k.c_str (), pn == k.size () ? pn : pn + 1) == 0;
}
protected:
int
compare (const C* x, size_type xn,
const C* y, size_type yn) const
{
size_type n (std::min (xn, yn));
int r (traits_type::compare (x, y, n));
if (r == 0)
{
// Pretend there is the delimiter characters at the end of the
// shorter string.
//
char xc (xn > n ? x[n] : (xn++, d_));
char yc (yn > n ? y[n] : (yn++, d_));
r = traits_type::compare (&xc, &yc, 1);
// If we are still equal, then compare the lengths.
//
if (r == 0)
r = (xn == yn ? 0 : (xn < yn ? -1 : 1));
}
return r;
}
private:
delimiter_type d_;
};
template <typename M>
struct prefix_map_common: M
{
typedef M map_type;
typedef typename map_type::key_type key_type;
typedef typename map_type::value_type value_type;
typedef typename map_type::key_compare compare_type;
typedef typename compare_type::delimiter_type delimiter_type;
typedef typename map_type::iterator iterator;
typedef typename map_type::const_iterator const_iterator;
explicit
prefix_map_common (delimiter_type d)
: map_type (compare_type (d)) {}
prefix_map_common (std::initializer_list<value_type> i, delimiter_type d)
: map_type (std::move (i), compare_type (d)) {}
std::pair<iterator, iterator>
find_prefix (const key_type&);
std::pair<const_iterator, const_iterator>
find_prefix (const key_type&) const;
};
template <typename M, typename prefix_map_common<M>::delimiter_type D>
struct prefix_map_impl: prefix_map_common<M>
{
typedef typename prefix_map_common<M>::value_type value_type;
prefix_map_impl (): prefix_map_common<M> (D) {}
prefix_map_impl (std::initializer_list<value_type> i)
: prefix_map_common<M> (std::move (i), D) {}
};
template <typename K,
typename T,
typename compare_prefix<K>::delimiter_type D>
using prefix_map = prefix_map_impl<std::map<K, T, compare_prefix<K>>, D>;
template <typename K,
typename T,
typename compare_prefix<K>::delimiter_type D>
using prefix_multimap =
prefix_map_impl<std::multimap<K, T, compare_prefix<K>>, D>;
}
#include <butl/prefix-map.txx>
#endif // BUTL_PREFIX_MAP
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