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+// file : libbutl/string-table.mxx -*- C++ -*-
+// copyright : Copyright (c) 2014-2017 Code Synthesis Ltd
+// license : MIT; see accompanying LICENSE file
+
+#ifndef __cpp_modules
+#pragma once
+#endif
+
+#include <cassert>
+
+#ifndef __cpp_lib_modules
+#include <string>
+#include <vector>
+#include <unordered_map>
+
+#include <limits> // numeric_limits
+#include <cstddef> // size_t
+#endif
+
+// Other includes.
+
+#ifdef __cpp_modules
+export module butl.string_table;
+#ifdef __cpp_lib_modules
+import std.core;
+#endif
+import butl.multi_index;
+#else
+#include <libbutl/multi-index.mxx>
+#endif
+
+#include <libbutl/export.hxx>
+
+LIBBUTL_MODEXPORT namespace butl
+{
+ // A pool of strings and, optionally, other accompanying data in which each
+ // entry is assigned an individual index (or id) of type I (e.g., uint8_t,
+ // uint16_t, etc., depending on how many entries are expected). Index value
+ // 0 is reserved to indicate the "no entry" condition.
+ //
+ template <typename I, typename D>
+ struct string_table_element
+ {
+ const I i;
+ const D d;
+ };
+
+ template <typename I>
+ struct string_table_element<I, std::string>
+ {
+ const I i;
+ const std::string d;
+ };
+
+ // For custom data the options are to call the data member 'key' or to
+ // specialize this traits.
+ //
+ template <typename D>
+ struct string_table_traits
+ {
+ static const std::string&
+ key (const D& d) {return d.key;}
+ };
+
+ template <>
+ struct string_table_traits<std::string>
+ {
+ static const std::string&
+ key (const std::string& d) {return d;}
+ };
+
+ template <typename I, typename D = std::string>
+ struct string_table
+ {
+ // Insert new entry unless one already exists.
+ //
+ I
+ insert (const D&);
+
+ // Find existing.
+ //
+ I
+ find (const std::string& k) const
+ {
+ auto i (map_.find (key_type (&k)));
+ return i != map_.end () ? i->second.i : 0;
+ }
+
+ // Reverse lookup.
+ //
+ const D&
+ operator[] (I i) const {assert (i > 0); return vec_[i - 1]->second.d;}
+
+ I
+ size () const {return static_cast<I> (vec_.size ());}
+
+ bool
+ empty () const {return vec_.empty ();}
+
+ void
+ clear () {vec_.clear (); map_.clear ();}
+
+ private:
+ using key_type = butl::map_key<std::string>;
+ using value_type = string_table_element<I, D>;
+ using map_type = std::unordered_map<key_type, value_type>;
+ using traits = string_table_traits<D>;
+
+ map_type map_;
+ std::vector<typename map_type::const_iterator> vec_;
+ };
+}
+
+#include <libbutl/string-table.txx>