Move string-table from build2 to libbutl

2 files changed, 119 insertions, 0 deletions

diff --git a/butl/string-table b/butl/string-table
new file mode 100644
index 0000000..e36ba08
--- /dev/null
+++ b/butl/string-table
@@ -0,0 +1,86 @@
+// file      : butl/string-table -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#ifndef BUTL_STRING_TABLE
+#define BUTL_STRING_TABLE
+
+#include <vector>
+#include <string>
+#include <unordered_map>
+
+#include <butl/multi-index>
+
+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;
+  };
+
+  template <typename D>
+  struct string_table_traits;
+
+  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 ();}
+
+  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 <butl/string-table.txx>
+
+#endif // BUTL_STRING_TABLE
diff --git a/butl/string-table.txx b/butl/string-table.txx
new file mode 100644
index 0000000..3e74997
--- /dev/null
+++ b/butl/string-table.txx
@@ -0,0 +1,33 @@
+// file      : butl/string-table.txx -*- C++ -*-
+// copyright : Copyright (c) 2014-2015 Code Synthesis Ltd
+// license   : MIT; see accompanying LICENSE file
+
+#include <limits>  // numeric_limits
+#include <cstddef> // size_t
+#include <cassert>
+
+namespace butl
+{
+  template <typename I, typename D>
+  I string_table<I, D>::
+  insert (const D& d)
+  {
+    std::size_t i (vec_.size () + 1);
+
+    // Note: move(d) would be tricky since the key still points to it.
+    //
+    auto r (map_.emplace (
+              key_type (&traits::key (d)),
+              value_type {static_cast<I> (i), d}));
+
+    if (r.second)
+    {
+      assert (i <= std::numeric_limits<I>::max ());
+
+      r.first->first.p = &traits::key (r.first->second.d); // Update key.
+      vec_.push_back (r.first);
+    }
+
+    return r.first->second.i;
+  }
+}