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.  The CACHE parameter is a hint as to whether it will be
  92   // useful to cache this data for later accesses--i.e., later calls
  93   // to get_view, read, or get_lasting_view which retrieve the same
  94   // data.
  95   const unsigned char*
  96   get_view(off_t start, off_t size, bool cache);
  97
  98   // Read data from the file into the buffer P starting at file offset
  99   // START for SIZE bytes.
 100   void
 101   read(off_t start, off_t size, void* p);
 102
 103   // Return a lasting view into the file starting at file offset START
 104   // for SIZE bytes.  This is allocated with new, and the caller is
 105   // responsible for deleting it when done.  The data associated with
 106   // this view will remain valid until the view is deleted.  It is an
 107   // error if we can not read enough data from the file.  The CACHE
 108   // parameter is as in get_view.
 109   File_view*
 110   get_lasting_view(off_t start, off_t size, bool cache);
 111
 112  private:
 113   // This class may not be copied.
 114   File_read(const File_read&);
 115   File_read& operator=(const File_read&);
 116
 117   // A view into the file.
 118   class View
 119   {
 120    public:
 121     View(off_t start, off_t size, const unsigned char* data, bool cache,
 122          bool mapped)
 123       : start_(start), size_(size), data_(data), lock_count_(0),
 124         cache_(cache), mapped_(mapped)
 125     { }
 126
 127     ~View();
 128
 129     off_t
 130     start() const
 131     { return this->start_; }
 132
 133     off_t
 134     size() const
 135     { return this->size_; }
 136
 137     const unsigned char*
 138     data() const
 139     { return this->data_; }
 140
 141     void
 142     lock();
 143
 144     void
 145     unlock();
 146
 147     bool
 148     is_locked();
 149
 150     void
 151     set_cache()
 152     { this->cache_ = true; }
 153
 154     bool
 155     should_cache() const
 156     { return this->cache_; }
 157
 158    private:
 159     View(const View&);
 160     View& operator=(const View&);
 161
 162     off_t start_;
 163     off_t size_;
 164     const unsigned char* data_;
 165     int lock_count_;
 166     bool cache_;
 167     bool mapped_;
 168   };
 169
 170   friend class File_view;
 171
 172   // Find a view into the file.
 173   View*
 174   find_view(off_t start, off_t size);
 175
 176   // Read data from the file into a buffer.
 177   void
 178   do_read(off_t start, off_t size, void* p);
 179
 180   // Find or make a view into the file.
 181   View*
 182   find_or_make_view(off_t start, off_t size, bool cache);
 183
 184   // Clear the file views.
 185   void
 186   clear_views(bool);
 187
 188   // The size of a file page for buffering data.
 189   static const off_t page_size = 8192;
 190
 191   // Given a file offset, return the page offset.
 192   static off_t
 193   page_offset(off_t file_offset)
 194   { return file_offset & ~ (page_size - 1); }
 195
 196   // Given a file size, return the size to read integral pages.
 197   static off_t
 198   pages(off_t file_size)
 199   { return (file_size + (page_size - 1)) & ~ (page_size - 1); }
 200
 201   // The type of a mapping from page start to views.
 202   typedef std::map<off_t, View*> Views;
 203
 204   // A simple list of Views.
 205   typedef std::list<View*> Saved_views;
 206
 207   // File name.
 208   std::string name_;
 209   // File descriptor.
 210   int descriptor_;
 211   // File size.
 212   off_t size_;
 213   // Number of locks on the file.
 214   int lock_count_;
 215   // Buffered views into the file.
 216   Views views_;
 217   // List of views which were locked but had to be removed from views_
 218   // because they were not large enough.
 219   Saved_views saved_views_;
 220   // Specified file contents.  Used only for testing purposes.
 221   const unsigned char* contents_;
 222 };
 223
 224 // A view of file data that persists even when the file is unlocked.
 225 // Callers should destroy these when no longer required.  These are
 226 // obtained form File_read::get_lasting_view.  They may only be
 227 // destroyed when the underlying File_read is locked.
 228
 229 class File_view
 230 {
 231  public:
 232   // This may only be called when the underlying File_read is locked.
 233   ~File_view();
 234
 235   // Return a pointer to the data associated with this view.
 236   const unsigned char*
 237   data() const
 238   { return this->data_; }
 239
 240  private:
 241   File_view(const File_view&);
 242   File_view& operator=(const File_view&);
 243
 244   friend class File_read;
 245
 246   // Callers have to get these via File_read::get_lasting_view.
 247   File_view(File_read& file, File_read::View* view, const unsigned char* data)
 248     : file_(file), view_(view), data_(data)
 249   { }
 250
 251   File_read& file_;
 252   File_read::View* view_;
 253   const unsigned char* data_;
 254 };
 255
 256 // All the information we hold for a single input file.  This can be
 257 // an object file, a shared library, or an archive.
 258
 259 class Input_file
 260 {
 261  public:
 262   Input_file(const Input_file_argument* input_argument)
 263     : input_argument_(input_argument), file_(), is_in_sysroot_(false)
 264   { }
 265
 266   // Create an input file with the contents already provided.  This is
 267   // only used for testing.  With this path, don't call the open
 268   // method.
 269   Input_file(const char* name, const unsigned char* contents, off_t size);
 270
 271   // Open the file.
 272   void
 273   open(const General_options&, const Dirsearch&);
 274
 275   // Return the name given by the user.
 276   const char*
 277   name() const
 278   { return this->input_argument_->name(); }
 279
 280   // Return the file name.
 281   const std::string&
 282   filename() const
 283   { return this->file_.filename(); }
 284
 285   // Return the position dependent options.
 286   const Position_dependent_options&
 287   options() const
 288   { return this->input_argument_->options(); }
 289
 290   // Return the file.
 291   File_read&
 292   file()
 293   { return this->file_; }
 294
 295   // Whether we found the file in a directory in the system root.
 296   bool
 297   is_in_sysroot() const
 298   { return this->is_in_sysroot_; }
 299
 300  private:
 301   Input_file(const Input_file&);
 302   Input_file& operator=(const Input_file&);
 303
 304   // The argument from the command line.
 305   const Input_file_argument* input_argument_;
 306   // The file after we open it.
 307   File_read file_;
 308   // Whether we found the file in a directory in the system root.
 309   bool is_in_sysroot_;
 310 };
 311
 312 } // end namespace gold
 313
 314 #endif // !defined(GOLD_FILEREAD_H)