gold/fileread.h

   1 // fileread.h -- read files for gold   -*- C++ -*-
   2
   3 // Copyright 2006, 2007 Free Software Foundation, Inc.
   4 // Written by Ian Lance Taylor <iant@google.com>.
   5
   6 // This file is part of gold.
   7
   8 // This program is free software; you can redistribute it and/or modify
   9 // it under the terms of the GNU General Public License as published by
  10 // the Free Software Foundation; either version 3 of the License, or
  11 // (at your option) any later version.
  12
  13 // This program is distributed in the hope that it will be useful,
  14 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 // GNU General Public License for more details.
  17
  18 // You should have received a copy of the GNU General Public License
  19 // along with this program; if not, write to the Free Software
  20 // Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,
  21 // MA 02110-1301, USA.
  22
  23 // Classes used to read data from binary input files.
  24
  25 #ifndef GOLD_FILEREAD_H
  26 #define GOLD_FILEREAD_H
  27
  28 #include <list>
  29 #include <map>
  30 #include <string>
  31
  32 #include "options.h"
  33
  34 namespace gold
  35 {
  36
  37 class Dirsearch;
  38 class File_view;
  39
  40 // File_read manages a file descriptor for a file we are reading.  We
  41 // close file descriptors if we run out of them, so this class reopens
  42 // the file as needed.
  43
  44 class File_read
  45 {
  46  public:
  47   File_read()
  48     : name_(), descriptor_(-1), lock_count_(0), views_(),
  49       saved_views_(), contents_(NULL), contents_size_(0)
  50   { }
  51
  52   ~File_read();
  53
  54   // Open a file.
  55   bool
  56   open(const std::string& name);
  57
  58   // Pretend to open the file, but provide the file contents.  No
  59   // actual file system activity will occur.  This is used for
  60   // testing.
  61   bool
  62   open(const std::string& name, const unsigned char* contents, off_t size);
  63
  64   // Return the file name.
  65   const std::string&
  66   filename() const
  67   { return this->name_; }
  68
  69   // Lock the file for access within a particular Task::run execution.
  70   // This means that the descriptor can not be closed.  This routine
  71   // may only be called from the main thread.
  72   void
  73   lock();
  74
  75   // Unlock the descriptor, permitting it to be closed if necessary.
  76   void
  77   unlock();
  78
  79   // Test whether the object is locked.
  80   bool
  81   is_locked();
  82
  83   // Return a view into the file.  The pointer will remain valid until
  84   // the File_read is unlocked.  If PBYTES is NULL, it is an error if
  85   // we can not read enough data.  Otherwise *PBYTES is set to the
  86   // number of bytes read.
  87   const unsigned char*
  88   get_view(off_t start, off_t size, off_t* pbytes = NULL);
  89
  90   // Read data from the file into the buffer P.  PBYTES is as in
  91   // get_view.
  92   void
  93   read(off_t start, off_t size, void* p, off_t* pbytes = NULL);
  94
  95   // Return a lasting view into the file.  This is allocated with new,
  96   // and the caller is responsible for deleting it when done.  The
  97   // data associated with this view will remain valid until the view
  98   // is deleted.  PBYTES is handled as with get_view.
  99   File_view*
 100   get_lasting_view(off_t start, off_t size, off_t *pbytes = NULL);
 101
 102  private:
 103   // This class may not be copied.
 104   File_read(const File_read&);
 105   File_read& operator=(const File_read&);
 106
 107   // A view into the file when not using mmap.
 108   class View
 109   {
 110    public:
 111     View(off_t start, off_t size, const unsigned char* data)
 112       : start_(start), size_(size), data_(data), lock_count_(0)
 113     { }
 114
 115     ~View();
 116
 117     off_t
 118     start() const
 119     { return this->start_; }
 120
 121     off_t
 122     size() const
 123     { return this->size_; }
 124
 125     const unsigned char*
 126     data() const
 127     { return this->data_; }
 128
 129     void
 130     lock();
 131
 132     void
 133     unlock();
 134
 135     bool
 136     is_locked();
 137
 138    private:
 139     View(const View&);
 140     View& operator=(const View&);
 141
 142     off_t start_;
 143     off_t size_;
 144     const unsigned char* data_;
 145     int lock_count_;
 146   };
 147
 148   friend class File_view;
 149
 150   // Find a view into the file.
 151   View*
 152   find_view(off_t start, off_t size);
 153
 154   // Read data from the file into a buffer.
 155   off_t
 156   do_read(off_t start, off_t size, void* p, off_t* pbytes);
 157
 158   // Find or make a view into the file.
 159   View*
 160   find_or_make_view(off_t start, off_t size, off_t* pbytes);
 161
 162   // Clear the file views.
 163   void
 164   clear_views(bool);
 165
 166   // The size of a file page for buffering data.
 167   static const off_t page_size = 8192;
 168
 169   // Given a file offset, return the page offset.
 170   static off_t
 171   page_offset(off_t file_offset)
 172   { return file_offset & ~ (page_size - 1); }
 173
 174   // Given a file size, return the size to read integral pages.
 175   static off_t
 176   pages(off_t file_size)
 177   { return (file_size + (page_size - 1)) & ~ (page_size - 1); }
 178
 179   // The type of a mapping from page start to views.
 180   typedef std::map<off_t, View*> Views;
 181
 182   // A simple list of Views.
 183   typedef std::list<View*> Saved_views;
 184
 185   // File name.
 186   std::string name_;
 187   // File descriptor.
 188   int descriptor_;
 189   // Number of locks on the file.
 190   int lock_count_;
 191   // Buffered views into the file.
 192   Views views_;
 193   // List of views which were locked but had to be removed from views_
 194   // because they were not large enough.
 195   Saved_views saved_views_;
 196   // Specified file contents.  Used only for testing purposes.
 197   const unsigned char* contents_;
 198   // Specified file size.  Used only for testing purposes.
 199   off_t contents_size_;
 200 };
 201
 202 // A view of file data that persists even when the file is unlocked.
 203 // Callers should destroy these when no longer required.  These are
 204 // obtained form File_read::get_lasting_view.  They may only be
 205 // destroyed when the underlying File_read is locked.
 206
 207 class File_view
 208 {
 209  public:
 210   // This may only be called when the underlying File_read is locked.
 211   ~File_view();
 212
 213   // Return a pointer to the data associated with this view.
 214   const unsigned char*
 215   data() const
 216   { return this->data_; }
 217
 218  private:
 219   File_view(const File_view&);
 220   File_view& operator=(const File_view&);
 221
 222   friend class File_read;
 223
 224   // Callers have to get these via File_read::get_lasting_view.
 225   File_view(File_read& file, File_read::View* view, const unsigned char* data)
 226     : file_(file), view_(view), data_(data)
 227   { }
 228
 229   File_read& file_;
 230   File_read::View* view_;
 231   const unsigned char* data_;
 232 };
 233
 234 // All the information we hold for a single input file.  This can be
 235 // an object file, a shared library, or an archive.
 236
 237 class Input_file
 238 {
 239  public:
 240   Input_file(const Input_file_argument* input_argument)
 241     : input_argument_(input_argument), file_()
 242   { }
 243
 244   // Create an input file with the contents already provided.  This is
 245   // only used for testing.  With this path, don't call the open
 246   // method.
 247   Input_file(const char* name, const unsigned char* contents, off_t size);
 248
 249   // Open the file.
 250   void
 251   open(const General_options&, const Dirsearch&);
 252
 253   // Return the name given by the user.
 254   const char*
 255   name() const
 256   { return this->input_argument_->name(); }
 257
 258   // Return the file name.
 259   const std::string&
 260   filename() const
 261   { return this->file_.filename(); }
 262
 263   // Return the position dependent options.
 264   const Position_dependent_options&
 265   options() const
 266   { return this->input_argument_->options(); }
 267
 268   // Return the file.
 269   File_read&
 270   file()
 271   { return this->file_; }
 272
 273  private:
 274   Input_file(const Input_file&);
 275   Input_file& operator=(const Input_file&);
 276
 277   const Input_file_argument* input_argument_;
 278   File_read file_;
 279 };
 280
 281 } // end namespace gold
 282
 283 #endif // !defined(GOLD_FILEREAD_H)