gold/fileread.h

   1 // fileread.h -- read files for gold   -*- C++ -*-
   2
   3 // Classes used to read data from binary input files.
   4
   5 #ifndef GOLD_FILEREAD_H
   6 #define GOLD_FILEREAD_H
   7
   8 #include <list>
   9 #include <map>
  10 #include <string>
  11
  12 #include "options.h"
  13
  14 namespace gold
  15 {
  16
  17 class Dirsearch;
  18 class File_view;
  19
  20 // File_read manages a file descriptor for a file we are reading.  We
  21 // close file descriptors if we run out of them, so this class reopens
  22 // the file as needed.
  23
  24 class File_read
  25 {
  26  public:
  27   File_read()
  28     : name_(), descriptor_(-1), lock_count_(0), views_(),
  29       saved_views_(), contents_(NULL), contents_size_(0)
  30   { }
  31
  32   ~File_read();
  33
  34   // Open a file.
  35   bool
  36   open(const std::string& name);
  37
  38   // Pretend to open the file, but provide the file contents.  No
  39   // actual file system activity will occur.  This is used for
  40   // testing.
  41   bool
  42   open(const std::string& name, const unsigned char* contents, off_t size);
  43
  44   // Return the file name.
  45   const std::string&
  46   filename() const
  47   { return this->name_; }
  48
  49   // Lock the file for access within a particular Task::run execution.
  50   // This means that the descriptor can not be closed.  This routine
  51   // may only be called from the main thread.
  52   void
  53   lock();
  54
  55   // Unlock the descriptor, permitting it to be closed if necessary.
  56   void
  57   unlock();
  58
  59   // Test whether the object is locked.
  60   bool
  61   is_locked();
  62
  63   // Return a view into the file.  The pointer will remain valid until
  64   // the File_read is unlocked.  If PBYTES is NULL, it is an error if
  65   // we can not read enough data.  Otherwise *PBYTES is set to the
  66   // number of bytes read.
  67   const unsigned char*
  68   get_view(off_t start, off_t size, off_t *pbytes = NULL);
  69
  70   // Read data from the file into the buffer P.  PBYTES is as in
  71   // get_view.
  72   void
  73   read(off_t start, off_t size, void* p, off_t *pbytes = NULL);
  74
  75   // Return a lasting view into the file.  This is allocated with new,
  76   // and the caller is responsible for deleting it when done.  The
  77   // data associated with this view will remain valid until the view
  78   // is deleted.  PBYTES is handled as with get_view.
  79   File_view*
  80   get_lasting_view(off_t start, off_t size, off_t *pbytes = NULL);
  81
  82  private:
  83   // This class may not be copied.
  84   File_read(const File_read&);
  85   File_read& operator=(const File_read&);
  86
  87   // A view into the file when not using mmap.
  88   class View
  89   {
  90    public:
  91     View(off_t start, off_t size, unsigned char* data)
  92       : start_(start), size_(size), data_(data), lock_count_(0)
  93     { }
  94
  95     ~View();
  96
  97     off_t
  98     start() const
  99     { return this->start_; }
 100
 101     off_t
 102     size() const
 103     { return this->size_; }
 104
 105     unsigned char*
 106     data() const
 107     { return this->data_; }
 108
 109     void
 110     lock();
 111
 112     void
 113     unlock();
 114
 115     bool
 116     is_locked();
 117
 118    private:
 119     View(const View&);
 120     View& operator=(const View&);
 121
 122     off_t start_;
 123     off_t size_;
 124     unsigned char* data_;
 125     int lock_count_;
 126   };
 127
 128   friend class File_view;
 129
 130   // Find a view into the file.
 131   View*
 132   find_view(off_t start, off_t size);
 133
 134   // Read data from the file into a buffer.
 135   off_t
 136   do_read(off_t start, off_t size, void* p, off_t* pbytes);
 137
 138   // Find or make a view into the file.
 139   View*
 140   find_or_make_view(off_t start, off_t size, off_t* pbytes);
 141
 142   // Clear the file views.
 143   void
 144   clear_views(bool);
 145
 146   // The size of a file page for buffering data.
 147   static const off_t page_size = 8192;
 148
 149   // Given a file offset, return the page offset.
 150   static off_t
 151   page_offset(off_t file_offset)
 152   { return file_offset & ~ (page_size - 1); }
 153
 154   // Given a file size, return the size to read integral pages.
 155   static off_t
 156   pages(off_t file_size)
 157   { return (file_size + (page_size - 1)) & ~ (page_size - 1); }
 158
 159   // The type of a mapping from page start to views.
 160   typedef std::map<off_t, View*> Views;
 161
 162   // A simple list of Views.
 163   typedef std::list<View*> Saved_views;
 164
 165   // File name.
 166   std::string name_;
 167   // File descriptor.
 168   int descriptor_;
 169   // Number of locks on the file.
 170   int lock_count_;
 171   // Buffered views into the file.
 172   Views views_;
 173   // List of views which were locked but had to be removed from views_
 174   // because they were not large enough.
 175   Saved_views saved_views_;
 176   // Specified file contents.  Used only for testing purposes.
 177   const unsigned char* contents_;
 178   // Specified file size.  Used only for testing purposes.
 179   off_t contents_size_;
 180 };
 181
 182 // A view of file data that persists even when the file is unlocked.
 183 // Callers should destroy these when no longer required.  These are
 184 // obtained form File_read::get_lasting_view.  They may only be
 185 // destroyed when the underlying File_read is locked.
 186
 187 class File_view
 188 {
 189  public:
 190   // This may only be called when the underlying File_read is locked.
 191   ~File_view();
 192
 193   // Return a pointer to the data associated with this view.
 194   const unsigned char*
 195   data() const
 196   { return this->data_; }
 197
 198  private:
 199   File_view(const File_view&);
 200   File_view& operator=(const File_view&);
 201
 202   friend class File_read;
 203
 204   // Callers have to get these via File_read::get_lasting_view.
 205   File_view(File_read& file, File_read::View* view, const unsigned char* data)
 206     : file_(file), view_(view), data_(data)
 207   { }
 208
 209   File_read& file_;
 210   File_read::View* view_;
 211   const unsigned char* data_;
 212 };
 213
 214 // All the information we hold for a single input file.  This can be
 215 // an object file, a shared library, or an archive.
 216
 217 class Input_file
 218 {
 219  public:
 220   Input_file(const Input_file_argument* input_argument)
 221     : input_argument_(input_argument), file_()
 222   { }
 223
 224   // Create an input file with the contents already provided.  This is
 225   // only used for testing.  With this path, don't call the open
 226   // method.
 227   Input_file(const char* name, const unsigned char* contents, off_t size);
 228
 229   // Open the file.
 230   void
 231   open(const General_options&, const Dirsearch&);
 232
 233   // Return the name given by the user.
 234   const char*
 235   name() const
 236   { return this->input_argument_->name(); }
 237
 238   // Return the file name.
 239   const std::string&
 240   filename() const
 241   { return this->file_.filename(); }
 242
 243   File_read&
 244   file()
 245   { return this->file_; }
 246
 247  private:
 248   Input_file(const Input_file&);
 249   Input_file& operator=(const Input_file&);
 250
 251   const Input_file_argument* input_argument_;
 252   File_read file_;
 253 };
 254
 255 } // end namespace gold
 256
 257 #endif // !defined(GOLD_FILEREAD_H)