gdb/dwarf2/abbrev-table-cache.h

   1 /* DWARF abbrev table cache
   2
   3    Copyright (C) 2022-2024 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef GDB_DWARF2_ABBREV_TABLE_CACHE_H
  21 #define GDB_DWARF2_ABBREV_TABLE_CACHE_H
  22
  23 #include "dwarf2/abbrev.h"
  24 #include "gdbsupport/unordered_set.h"
  25
  26 /* An abbrev table cache holds abbrev tables for easier reuse.  */
  27 class abbrev_table_cache
  28 {
  29 public:
  30   abbrev_table_cache () = default;
  31   DISABLE_COPY_AND_ASSIGN (abbrev_table_cache);
  32
  33   /* Find an abbrev table coming from the abbrev section SECTION at
  34      offset OFFSET.  Return the table, or nullptr if it has not yet
  35      been registered.  */
  36   const abbrev_table *find (dwarf2_section_info *section,
  37                             sect_offset offset) const
  38   {
  39     abbrev_table_search_key key {section, offset};
  40
  41     if (auto iter = m_tables.find (key);
  42         iter != m_tables.end ())
  43       return iter->get ();
  44
  45     return nullptr;
  46   }
  47
  48   /* Add TABLE to this cache.  Ownership of TABLE is transferred to
  49      the cache.  Note that a table at a given section+offset may only
  50      be registered once -- a violation of this will cause an assert.
  51      To avoid this, call the 'find' method first, to see if the table
  52      has already been read.  */
  53   void add (abbrev_table_up table);
  54
  55 private:
  56   /* Key used to search for an existing abbrev table in M_TABLES.  */
  57   struct abbrev_table_search_key
  58   {
  59     const dwarf2_section_info *section;
  60     sect_offset sect_off;
  61   };
  62
  63   struct abbrev_table_hash
  64   {
  65     using is_transparent = void;
  66
  67     std::size_t operator() (const abbrev_table_search_key &key) const noexcept
  68     {
  69       return (std::hash<const dwarf2_section_info *> () (key.section)
  70               + (std::hash<std::underlying_type_t<decltype (key.sect_off)>> ()
  71                  (to_underlying (key.sect_off))));
  72     }
  73
  74     std::size_t operator() (const abbrev_table_up &table) const noexcept
  75     { return (*this) ({ table->section, table->sect_off }); }
  76   };
  77
  78   struct abbrev_table_eq
  79   {
  80     using is_transparent = void;
  81
  82     bool operator() (const abbrev_table_search_key &key,
  83                      const abbrev_table_up &table) const noexcept
  84     { return key.section == table->section && key.sect_off == table->sect_off; }
  85
  86     bool operator() (const abbrev_table_up &lhs,
  87                      const abbrev_table_up &rhs) const noexcept
  88     { return (*this) ({ lhs->section, lhs->sect_off }, rhs); }
  89   };
  90
  91   /* Hash table of abbrev tables.  */
  92   gdb::unordered_set<abbrev_table_up, abbrev_table_hash, abbrev_table_eq> m_tables;
  93 };
  94
  95 #endif /* GDB_DWARF2_ABBREV_TABLE_CACHE_H */