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// descriptors.h -- manage file descriptors for gold   -*- C++ -*-

// Copyright 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.

#ifndef GOLD_DESCRIPTORS_H

#define GOLD_DESCRIPTORS_H

#include <vector>

namespace gold

{

class Lock;

// This class manages file descriptors for gold.

class Descriptors

{

 public:

  Descriptors();

  // Get a file descriptor for a file.  The DESCRIPTOR parameter is

  // the descriptor the last time the file was used; this will be -1

  // if this is the first time the file is being opened.  The NAME,

  // FLAGS, and MODE parameters are as for ::open.  NAME must be in

  // permanent storage.  This returns the descriptor to use, which may

  // or may not be the same as DESCRIPTOR.  If there is an error

  // opening the file, this will return -1 with errno set

  // appropriately.

  int

  open(int descriptor, const char* name, int flags, int mode = 0);

  // Release the file descriptor DESCRIPTOR.  If PERMANENT is true, it

  // will be closed, and the caller may not reopen it.  If PERMANENT

  // is false this doesn't necessarily close the descriptor, but it

  // makes it available to be closed; the descriptor must not be used

  // again except as an argument to Descriptor::open.

  void

  release(int descriptor, bool permanent);

 private:

  // Information kept for a descriptor.

  struct Open_descriptor

  {

    // File name currently associated with descriptor.  This is empty

    // if none.

    const char* name;

    // Index of next descriptor on stack of released descriptors.

    int stack_next;

    // Whether the descriptor is currently in use.

    bool inuse;

    // Whether this is a write descriptor.

    bool is_write;

  };

  bool

  close_some_descriptor();

  // We need to lock before accessing any fields.

  Lock* lock_;

  // Information for descriptors.

  std::vector<Open_descriptor> open_descriptors_;

  // Top of stack.

  int stack_top_;

  // The current number of file descriptors open.

  int current_;

  // The maximum number of file descriptors we open.

  int limit_;

};

// File descriptors are a centralized data structure, and we use a

// global variable rather than passing the data structure into every

// routine that does file I/O.

extern Descriptors descriptors;

inline int

open_descriptor(int descriptor, const char* name, int flags, int mode = 0)

{ return descriptors.open(descriptor, name, flags, mode); }

inline void

release_descriptor(int descriptor, bool permanent)

{ descriptors.release(descriptor, permanent); }

} // End namespace gold.

#endif // !defined(GOLD_DESCRIPTORS_H)