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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