gdb/dwarf2/index-cache.h

   1 /* Caching of GDB/DWARF index files.
   2
   3    Copyright (C) 2018-2020 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 DWARF_INDEX_CACHE_H
  21 #define DWARF_INDEX_CACHE_H
  22
  23 #include "dwarf2/index-common.h"
  24 #include "gdbsupport/array-view.h"
  25 #include "symfile.h"
  26
  27 /* Base of the classes used to hold the resources of the indices loaded from
  28    the cache (e.g. mmapped files).  */
  29
  30 struct index_cache_resource
  31 {
  32   virtual ~index_cache_resource () = 0;
  33 };
  34
  35 /* Class to manage the access to the DWARF index cache.  */
  36
  37 class index_cache
  38 {
  39 public:
  40   /* Change the directory used to save/load index files.  */
  41   void set_directory (std::string dir);
  42
  43   /* Return true if the usage of the cache is enabled.  */
  44   bool enabled () const
  45   {
  46     return m_enabled;
  47   }
  48
  49   /* Enable the cache.  */
  50   void enable ();
  51
  52   /* Disable the cache.  */
  53   void disable ();
  54
  55   /* Store an index for the specified object file in the cache.  */
  56   void store (dwarf2_per_objfile *per_objfile);
  57
  58   /* Look for an index file matching BUILD_ID.  If found, return the contents
  59      as an array_view and store the underlying resources (allocated memory,
  60      mapped file, etc) in RESOURCE.  The returned array_view is valid as long
  61      as RESOURCE is not destroyed.
  62
  63      If no matching index file is found, return an empty array view.  */
  64   gdb::array_view<const gdb_byte>
  65   lookup_gdb_index (const bfd_build_id *build_id,
  66                     std::unique_ptr<index_cache_resource> *resource);
  67
  68   /* Return the number of cache hits.  */
  69   unsigned int n_hits () const
  70   { return m_n_hits; }
  71
  72   /* Record a cache hit.  */
  73   void hit ()
  74   {
  75     if (enabled ())
  76       m_n_hits++;
  77   }
  78
  79   /* Return the number of cache misses.  */
  80   unsigned int n_misses () const
  81   { return m_n_misses; }
  82
  83   /* Record a cache miss.  */
  84   void miss ()
  85   {
  86     if (enabled ())
  87       m_n_misses++;
  88   }
  89
  90 private:
  91
  92   /* Compute the absolute filename where the index of the objfile with build
  93      id BUILD_ID will be stored.  SUFFIX is appended at the end of the
  94      filename.  */
  95   std::string make_index_filename (const bfd_build_id *build_id,
  96                                    const char *suffix) const;
  97
  98   /* The base directory where we are storing and looking up index files.  */
  99   std::string m_dir;
 100
 101   /* Whether the cache is enabled.  */
 102   bool m_enabled = false;
 103
 104   /* Number of cache hits and misses during this GDB session.  */
 105   unsigned int m_n_hits = 0;
 106   unsigned int m_n_misses = 0;
 107 };
 108
 109 /* The global instance of the index cache.  */
 110 extern index_cache global_index_cache;
 111
 112 #endif /* DWARF_INDEX_CACHE_H */