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diff --git a/gdb/dwarf2/mapped-index.h b/gdb/dwarf2/mapped-index.h
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+/* Base class for mapped indices
+
+   Copyright (C) 2021, 2022 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#ifndef GDB_DWARF2_MAPPED_INDEX_H
+#define GDB_DWARF2_MAPPED_INDEX_H
+
+#include "language.h"
+
+/* An index into a (C++) symbol name component in a symbol name as
+   recorded in the mapped_index's symbol table.  For each C++ symbol
+   in the symbol table, we record one entry for the start of each
+   component in the symbol in a table of name components, and then
+   sort the table, in order to be able to binary search symbol names,
+   ignoring leading namespaces, both completion and regular look up.
+   For example, for symbol "A::B::C", we'll have an entry that points
+   to "A::B::C", another that points to "B::C", and another for "C".
+   Note that function symbols in GDB index have no parameter
+   information, just the function/method names.  You can convert a
+   name_component to a "const char *" using the
+   'mapped_index::symbol_name_at(offset_type)' method.  */
+
+struct name_component
+{
+  /* Offset in the symbol name where the component starts.  Stored as
+     a (32-bit) offset instead of a pointer to save memory and improve
+     locality on 64-bit architectures.  */
+  offset_type name_offset;
+
+  /* The symbol's index in the symbol and constant pool tables of a
+     mapped_index.  */
+  offset_type idx;
+};
+
+class cooked_index_vector;
+
+/* Base class of all DWARF scanner types.  */
+
+struct dwarf_scanner_base
+{
+  dwarf_scanner_base () = default;
+  virtual ~dwarf_scanner_base () = default;
+  DISABLE_COPY_AND_ASSIGN (dwarf_scanner_base);
+
+  /* Return a quick_symbol_functions instance that refers back to this
+     dwarf_scanner_base.  */
+  virtual quick_symbol_functions_up make_quick_functions () const = 0;
+
+  /* An ad hoc version check.  This is needed for .gdb_index to check
+     whether a version 8 or above index is in use.  Returns true if
+     the index is usable, false otherwise.  */
+  virtual bool version_check () const
+  {
+    return true;
+  }
+
+  /* This is called when writing an index.  For a cooked index, it
+     will return 'this' as a cooked index.  For other forms, it will
+     throw an exception with an appropriate error message.  */
+  virtual cooked_index_vector *index_for_writing () = 0;
+};
+
+/* Base class containing bits shared by both .gdb_index and
+   .debug_name indexes.  */
+
+struct mapped_index_base : public dwarf_scanner_base
+{
+  mapped_index_base () = default;
+  DISABLE_COPY_AND_ASSIGN (mapped_index_base);
+
+  /* The name_component table (a sorted vector).  See name_component's
+     description above.  */
+  std::vector<name_component> name_components;
+
+  /* How NAME_COMPONENTS is sorted.  */
+  enum case_sensitivity name_components_casing;
+
+  /* Return the number of names in the symbol table.  */
+  virtual size_t symbol_name_count () const = 0;
+
+  /* Get the name of the symbol at IDX in the symbol table.  */
+  virtual const char *symbol_name_at
+    (offset_type idx, dwarf2_per_objfile *per_objfile) const = 0;
+
+  /* Return whether the name at IDX in the symbol table should be
+     ignored.  */
+  virtual bool symbol_name_slot_invalid (offset_type idx) const
+  {
+    return false;
+  }
+
+  /* Build the symbol name component sorted vector, if we haven't
+     yet.  */
+  void build_name_components (dwarf2_per_objfile *per_objfile);
+
+  /* Returns the lower (inclusive) and upper (exclusive) bounds of the
+     possible matches for LN_NO_PARAMS in the name component
+     vector.  */
+  std::pair<std::vector<name_component>::const_iterator,
+	    std::vector<name_component>::const_iterator>
+    find_name_components_bounds (const lookup_name_info &ln_no_params,
+				 enum language lang,
+				 dwarf2_per_objfile *per_objfile) const;
+
+  cooked_index_vector *index_for_writing () override
+  {
+    error (_("Cannot use an index to create the index"));
+  }
+};
+
+#endif /* GDB_DWARF2_MAPPED_INDEX_H */