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// fileread.h -- read files for gold   -*- C++ -*-

// Copyright 2006, 2007, 2008 Free Software Foundation, Inc.

// Written by Ian Lance Taylor <iant@google.com>.

// This file is part of gold.

// This program is free software; you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation; either version 3 of the License, or

// (at your option) any later version.

// This program is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License

// along with this program; if not, write to the Free Software

// Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

// MA 02110-1301, USA.

// Classes used to read data from binary input files.

#ifndef GOLD_FILEREAD_H

#define GOLD_FILEREAD_H

#include <list>

#include <map>

#include <string>

#include <vector>

#include "token.h"

namespace gold

{

class Position_dependent_options;

class Input_file_argument;

class Dirsearch;

class File_view;

// File_read manages a file descriptor and mappings for a file we are

// reading.

class File_read

{

 public:

  File_read()

    : name_(), descriptor_(-1), is_descriptor_opened_(false), object_count_(0),

      size_(0), token_(false), views_(), saved_views_(), contents_(NULL),

      mapped_bytes_(0), released_(true)

  { }

  ~File_read();

  // Open a file.

  bool

  open(const Task*, const std::string& name);

  // Pretend to open the file, but provide the file contents.  No

  // actual file system activity will occur.  This is used for

  // testing.

  bool

  open(const Task*, const std::string& name, const unsigned char* contents,

       off_t size);

  // Return the file name.

  const std::string&

  filename() const

  { return this->name_; }

  // Add an object associated with a file.

  void

  add_object()

  { ++this->object_count_; }

  // Remove an object associated with a file.

  void

  remove_object()

  { --this->object_count_; }

  // Lock the file for exclusive access within a particular Task::run

  // execution.  This routine may only be called when the workqueue

  // lock is held.

  void

  lock(const Task* t);

  // Unlock the file.

  void

  unlock(const Task* t);

  // Test whether the object is locked.

  bool

  is_locked() const;

  // Return the token, so that the task can be queued.

  Task_token*

  token()

  { return &this->token_; }

  // Release the file.  This indicates that we aren't going to do

  // anything further with it until it is unlocked.  This is used

  // because a Task which locks the file never calls either lock or

  // unlock; it just locks the token.  The basic rule is that a Task

  // which locks a file via the Task::locks interface must explicitly

  // call release() when it is done.  This is not necessary for code

  // which calls unlock() on the file.

  void

  release();

  // Return the size of the file.

  off_t

  filesize() const

  { return this->size_; }

  // Return a view into the file starting at file offset START for

  // SIZE bytes.  OFFSET is the offset into the input file for the

  // file we are reading; this is zero for a normal object file,

  // non-zero for an object file in an archive.  ALIGNED is true if

  // the data must be naturally aligned; this only matters when OFFSET

  // is not zero.  The pointer will remain valid until the File_read

  // is unlocked.  It is an error if we can not read enough data from

  // the file.  The CACHE parameter is a hint as to whether it will be

  // useful to cache this data for later accesses--i.e., later calls

  // to get_view, read, or get_lasting_view which retrieve the same

  // data.

  const unsigned char*

  get_view(off_t offset, off_t start, section_size_type size, bool aligned,

           bool cache);

  // Read data from the file into the buffer P starting at file offset

  // START for SIZE bytes.

  void

  read(off_t start, section_size_type size, void* p);

  // Return a lasting view into the file starting at file offset START

  // for SIZE bytes.  This is allocated with new, and the caller is

  // responsible for deleting it when done.  The data associated with

  // this view will remain valid until the view is deleted.  It is an

  // error if we can not read enough data from the file.  The OFFSET,

  // ALIGNED and CACHE parameters are as in get_view.

  File_view*

  get_lasting_view(off_t offset, off_t start, section_size_type size,

                   bool aligned, bool cache);

  // Mark all views as no longer cached.

  void

  clear_view_cache_marks();

  // Discard all uncached views.  This is normally done by release(),

  // but not for objects in archives.  FIXME: This is a complicated

  // interface, and it would be nice to have something more automatic.

  void

  clear_uncached_views()

  { this->clear_views(false); }

  // A struct used to do a multiple read.

  struct Read_multiple_entry

  {

    // The file offset of the data to read.

    off_t file_offset;

    // The amount of data to read.

    section_size_type size;

    // The buffer where the data should be placed.

    unsigned char* buffer;

    Read_multiple_entry(off_t o, section_size_type s, unsigned char* b)

      : file_offset(o), size(s), buffer(b)

    { }

  };

  typedef std::vector<Read_multiple_entry> Read_multiple;

  // Read a bunch of data from the file into various different

  // locations.  The vector must be sorted by ascending file_offset.

  // BASE is a base offset to be added to all the offsets in the

  // vector.

  void

  read_multiple(off_t base, const Read_multiple&);

  // Dump statistical information to stderr.

  static void

  print_stats();

 private:

  // This class may not be copied.

  File_read(const File_read&);

  File_read& operator=(const File_read&);

  // Total bytes mapped into memory during the link.  This variable

  // may not be accurate when running multi-threaded.

  static unsigned long long total_mapped_bytes;

  // Current number of bytes mapped into memory during the link.  This

  // variable may not be accurate when running multi-threaded.

  static unsigned long long current_mapped_bytes;

  // High water mark of bytes mapped into memory during the link.

  // This variable may not be accurate when running multi-threaded.

  static unsigned long long maximum_mapped_bytes;

  // A view into the file.

  class View

  {

   public:

    View(off_t start, section_size_type size, const unsigned char* data,

         unsigned int byteshift, bool cache, bool mapped)

      : start_(start), size_(size), data_(data), lock_count_(0),

        byteshift_(byteshift), cache_(cache), mapped_(mapped), accessed_(true)

    { }

    ~View();

    off_t

    start() const

    { return this->start_; }

    section_size_type

    size() const

    { return this->size_; }

    const unsigned char*

    data() const

    { return this->data_; }

    void

    lock();

    void

    unlock();

    bool

    is_locked();

    unsigned int

    byteshift() const

    { return this->byteshift_; }

    void

    set_cache()

    { this->cache_ = true; }

    void

    clear_cache()

    { this->cache_ = false; }

    bool

    should_cache() const

    { return this->cache_; }

    void

    set_accessed()

    { this->accessed_ = true; }

    void

    clear_accessed()

    { this->accessed_= false; }

    bool

    accessed() const

    { return this->accessed_; }

   private:

    View(const View&);

    View& operator=(const View&);

    // The file offset of the start of the view.

    off_t start_;

    // The size of the view.

    section_size_type size_;

    // A pointer to the actual bytes.

    const unsigned char* data_;

    // The number of locks on this view.

    int lock_count_;

    // The number of bytes that the view is shifted relative to the

    // underlying file.  This is used to align data.  This is normally

    // zero, except possibly for an object in an archive.

    unsigned int byteshift_;

    // Whether the view is cached.

    bool cache_;

    // Whether the view is mapped into memory.  If not, data_ points

    // to memory allocated using new[].

    bool mapped_;

    // Whether the view has been accessed recently.

    bool accessed_;

  };

  friend class View;

  friend class File_view;

  // The type of a mapping from page start and byte shift to views.

  typedef std::map<std::pair<off_t, unsigned int>, View*> Views;

  // A simple list of Views.

  typedef std::list<View*> Saved_views;

  // Open the descriptor if necessary.

  void

  reopen_descriptor();

  // Find a view into the file.

  View*

  find_view(off_t start, section_size_type size, unsigned int byteshift,

            View** vshifted) const;

  // Read data from the file into a buffer.

  void

  do_read(off_t start, section_size_type size, void* p);

  // Add a view.

  void

  add_view(View*);

  // Make a view into the file.

  View*

  make_view(off_t start, section_size_type size, unsigned int byteshift,

            bool cache);

  // Find or make a view into the file.

  View*

  find_or_make_view(off_t offset, off_t start, section_size_type size,

                    bool aligned, bool cache);

  // Clear the file views.

  void

  clear_views(bool);

  // The size of a file page for buffering data.

  static const off_t page_size = 8192;

  // Given a file offset, return the page offset.

  static off_t

  page_offset(off_t file_offset)

  { return file_offset & ~ (page_size - 1); }

  // Given a file size, return the size to read integral pages.

  static off_t

  pages(off_t file_size)

  { return (file_size + (page_size - 1)) & ~ (page_size - 1); }

  // The maximum number of entries we will pass to ::readv.

  static const size_t max_readv_entries = 128;

  // Use readv to read data.

  void

  do_readv(off_t base, const Read_multiple&, size_t start, size_t count);

  // File name.

  std::string name_;

  // File descriptor.

  int descriptor_;

  // Whether we have regained the descriptor after releasing the file.

  bool is_descriptor_opened_;

  // The number of objects associated with this file.  This will be

  // more than 1 in the case of an archive.

  int object_count_;

  // File size.

  off_t size_;

  // A token used to lock the file.

  Task_token token_;

  // Buffered views into the file.

  Views views_;

  // List of views which were locked but had to be removed from views_

  // because they were not large enough.

  Saved_views saved_views_;

  // Specified file contents.  Used only for testing purposes.

  const unsigned char* contents_;

  // Total amount of space mapped into memory.  This is only changed

  // while the file is locked.  When we unlock the file, we transfer

  // the total to total_mapped_bytes, and reset this to zero.

  size_t mapped_bytes_;

  // Whether the file was released.

  bool released_;

};

// A view of file data that persists even when the file is unlocked.

// Callers should destroy these when no longer required.  These are

// obtained form File_read::get_lasting_view.  They may only be

// destroyed when the underlying File_read is locked.

class File_view

{

 public:

  // This may only be called when the underlying File_read is locked.

  ~File_view();

  // Return a pointer to the data associated with this view.

  const unsigned char*

  data() const

  { return this->data_; }

 private:

  File_view(const File_view&);

  File_view& operator=(const File_view&);

  friend class File_read;

  // Callers have to get these via File_read::get_lasting_view.

  File_view(File_read& file, File_read::View* view, const unsigned char* data)

    : file_(file), view_(view), data_(data)

  { }

  File_read& file_;

  File_read::View* view_;

  const unsigned char* data_;

};

// All the information we hold for a single input file.  This can be

// an object file, a shared library, or an archive.

class Input_file

{

 public:

  Input_file(const Input_file_argument* input_argument)

    : input_argument_(input_argument), found_name_(), file_(),

      is_in_sysroot_(false)

  { }

  // Create an input file with the contents already provided.  This is

  // only used for testing.  With this path, don't call the open

  // method.

  Input_file(const Task*, const char* name, const unsigned char* contents,

             off_t size);

  // Open the file.  If the open fails, this will report an error and

  // return false.

  bool

  open(const General_options&, const Dirsearch&, const Task*);

  // Return the name given by the user.  For -lc this will return "c".

  const char*

  name() const;

  // Return the file name.  For -lc this will return something like

  // "/usr/lib/libc.so".

  const std::string&

  filename() const

  { return this->file_.filename(); }

  // Return the name under which we found the file, corresponding to

  // the command line.  For -lc this will return something like

  // "libc.so".

  const std::string&

  found_name() const

  { return this->found_name_; }

  // Return the position dependent options.

  const Position_dependent_options&

  options() const;

  // Return the file.

  File_read&

  file()

  { return this->file_; }

  const File_read&

  file() const

  { return this->file_; }

  // Whether we found the file in a directory in the system root.

  bool

  is_in_sysroot() const

  { return this->is_in_sysroot_; }

  // Return whether this file is to be read only for its symbols.

  bool

  just_symbols() const;

 private:

  Input_file(const Input_file&);

  Input_file& operator=(const Input_file&);

  // Open a binary file.

  bool

  open_binary(const General_options&, const Task* task,

              const std::string& name);

  // The argument from the command line.

  const Input_file_argument* input_argument_;

  // The name under which we opened the file.  This is like the name

  // on the command line, but -lc turns into libc.so (or whatever).

  // It only includes the full path if the path was on the command

  // line.

  std::string found_name_;

  // The file after we open it.

  File_read file_;

  // Whether we found the file in a directory in the system root.

  bool is_in_sysroot_;

};

} // end namespace gold

#endif // !defined(GOLD_FILEREAD_H)