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), size_(0), lock_count_(0), views_(),
  49       saved_views_(), contents_(NULL)
  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 the size of the file.
  84   off_t
  85   filesize() const
  86   { return this->size_; }
  87
  88   // Return a view into the file starting at file offset START for
  89   // SIZE bytes.  The pointer will remain valid until the File_read is
  90   // unlocked.  It is an error if we can not read enough data from the
  91   // file.
  92   const unsigned char*
  93   get_view(off_t start, off_t size);
  94
  95   // Read data from the file into the buffer P starting at file offset
  96   // START for SIZE bytes.
  97   void
  98   read(off_t start, off_t size, void* p);
  99
 100   // Return a lasting view into the file starting at file offset START
 101   // for SIZE bytes.  This is allocated with new, and the caller is
 102   // responsible for deleting it when done.  The data associated with
 103   // this view will remain valid until the view is deleted.  It is an
 104   // error if we can not read enough data from the file.
 105   File_view*
 106   get_lasting_view(off_t start, off_t size);
 107
 108  private:
 109   // This class may not be copied.
 110   File_read(const File_read&);
 111   File_read& operator=(const File_read&);
 112
 113   // A view into the file when not using mmap.
 114   class View
 115   {
 116    public:
 117     View(off_t start, off_t size, const unsigned char* data)
 118       : start_(start), size_(size), data_(data), lock_count_(0)
 119     { }
 120
 121     ~View();
 122
 123     off_t
 124     start() const
 125     { return this->start_; }
 126
 127     off_t
 128     size() const
 129     { return this->size_; }
 130
 131     const unsigned char*
 132     data() const
 133     { return this->data_; }
 134
 135     void
 136     lock();
 137
 138     void
 139     unlock();
 140
 141     bool
 142     is_locked();
 143
 144    private:
 145     View(const View&);
 146     View& operator=(const View&);
 147
 148     off_t start_;
 149     off_t size_;
 150     const unsigned char* data_;
 151     int lock_count_;
 152   };
 153
 154   friend class File_view;
 155
 156   // Find a view into the file.
 157   View*
 158   find_view(off_t start, off_t size);
 159
 160   // Read data from the file into a buffer.
 161   off_t
 162   do_read(off_t start, off_t size, void* p);
 163
 164   // Read an exact number of bytes into a buffer.
 165   void
 166   do_read_exact(off_t start, off_t size, void* p);
 167
 168   // Find or make a view into the file.
 169   View*
 170   find_or_make_view(off_t start, off_t size);
 171
 172   // Clear the file views.
 173   void
 174   clear_views(bool);
 175
 176   // The size of a file page for buffering data.
 177   static const off_t page_size = 8192;
 178
 179   // Given a file offset, return the page offset.
 180   static off_t
 181   page_offset(off_t file_offset)
 182   { return file_offset & ~ (page_size - 1); }
 183
 184   // Given a file size, return the size to read integral pages.
 185   static off_t
 186   pages(off_t file_size)
 187   { return (file_size + (page_size - 1)) & ~ (page_size - 1); }
 188
 189   // The type of a mapping from page start to views.
 190   typedef std::map<off_t, View*> Views;
 191
 192   // A simple list of Views.
 193   typedef std::list<View*> Saved_views;
 194
 195   // File name.
 196   std::string name_;
 197   // File descriptor.
 198   int descriptor_;
 199   // File size.
 200   off_t size_;
 201   // Number of locks on the file.
 202   int lock_count_;
 203   // Buffered views into the file.
 204   Views views_;
 205   // List of views which were locked but had to be removed from views_
 206   // because they were not large enough.
 207   Saved_views saved_views_;
 208   // Specified file contents.  Used only for testing purposes.
 209   const unsigned char* contents_;
 210 };
 211
 212 // A view of file data that persists even when the file is unlocked.
 213 // Callers should destroy these when no longer required.  These are
 214 // obtained form File_read::get_lasting_view.  They may only be
 215 // destroyed when the underlying File_read is locked.
 216
 217 class File_view
 218 {
 219  public:
 220   // This may only be called when the underlying File_read is locked.
 221   ~File_view();
 222
 223   // Return a pointer to the data associated with this view.
 224   const unsigned char*
 225   data() const
 226   { return this->data_; }
 227
 228  private:
 229   File_view(const File_view&);
 230   File_view& operator=(const File_view&);
 231
 232   friend class File_read;
 233
 234   // Callers have to get these via File_read::get_lasting_view.
 235   File_view(File_read& file, File_read::View* view, const unsigned char* data)
 236     : file_(file), view_(view), data_(data)
 237   { }
 238
 239   File_read& file_;
 240   File_read::View* view_;
 241   const unsigned char* data_;
 242 };
 243
 244 // All the information we hold for a single input file.  This can be
 245 // an object file, a shared library, or an archive.
 246
 247 class Input_file
 248 {
 249  public:
 250   Input_file(const Input_file_argument* input_argument)
 251     : input_argument_(input_argument), file_()
 252   { }
 253
 254   // Create an input file with the contents already provided.  This is
 255   // only used for testing.  With this path, don't call the open
 256   // method.
 257   Input_file(const char* name, const unsigned char* contents, off_t size);
 258
 259   // Open the file.
 260   void
 261   open(const General_options&, const Dirsearch&);
 262
 263   // Return the name given by the user.
 264   const char*
 265   name() const
 266   { return this->input_argument_->name(); }
 267
 268   // Return the file name.
 269   const std::string&
 270   filename() const
 271   { return this->file_.filename(); }
 272
 273   // Return the position dependent options.
 274   const Position_dependent_options&
 275   options() const
 276   { return this->input_argument_->options(); }
 277
 278   // Return the file.
 279   File_read&
 280   file()
 281   { return this->file_; }
 282
 283  private:
 284   Input_file(const Input_file&);
 285   Input_file& operator=(const Input_file&);
 286
 287   const Input_file_argument* input_argument_;
 288   File_read file_;
 289 };
 290
 291 } // end namespace gold
 292
 293 #endif // !defined(GOLD_FILEREAD_H)