1// descriptors.h -- manage file descriptors for gold   -*- C++ -*-
2
3// Copyright (C) 2008-2017 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#ifndef GOLD_DESCRIPTORS_H
24#define GOLD_DESCRIPTORS_H
25
26#include <vector>
27
28#include "gold-threads.h"
29
30namespace gold
31{
32
33// This class manages file descriptors for gold.
34
35class Descriptors
36{
37 public:
38  Descriptors();
39
40  // Get a file descriptor for a file.  The DESCRIPTOR parameter is
41  // the descriptor the last time the file was used; this will be -1
42  // if this is the first time the file is being opened.  The NAME,
43  // FLAGS, and MODE parameters are as for ::open.  NAME must be in
44  // permanent storage.  This returns the descriptor to use, which may
45  // or may not be the same as DESCRIPTOR.  If there is an error
46  // opening the file, this will return -1 with errno set
47  // appropriately.
48  int
49  open(int descriptor, const char* name, int flags, int mode = 0);
50
51  // Release the file descriptor DESCRIPTOR.  If PERMANENT is true, it
52  // will be closed, and the caller may not reopen it.  If PERMANENT
53  // is false this doesn't necessarily close the descriptor, but it
54  // makes it available to be closed; the descriptor must not be used
55  // again except as an argument to Descriptor::open.
56  void
57  release(int descriptor, bool permanent);
58
59  // Close all the descriptors open for reading.
60  void
61  close_all();
62
63 private:
64  // Information kept for a descriptor.
65  struct Open_descriptor
66  {
67    // File name currently associated with descriptor.  This is empty
68    // if none.
69    const char* name;
70    // Index of next descriptor on stack of released descriptors.
71    int stack_next;
72    // Whether the descriptor is currently in use.
73    bool inuse;
74    // Whether this is a write descriptor.
75    bool is_write;
76    // Whether the descriptor is on the stack.
77    bool is_on_stack;
78  };
79
80  bool
81  close_some_descriptor();
82
83  // We need to lock before accessing any fields.
84  Lock* lock_;
85  // Used to initialize the lock_ field exactly once.
86  Initialize_lock initialize_lock_;
87  // Information for descriptors.
88  std::vector<Open_descriptor> open_descriptors_;
89  // Top of stack.
90  int stack_top_;
91  // The current number of file descriptors open.
92  int current_;
93  // The maximum number of file descriptors we open.
94  int limit_;
95};
96
97// File descriptors are a centralized data structure, and we use a
98// global variable rather than passing the data structure into every
99// routine that does file I/O.
100
101extern Descriptors descriptors;
102
103inline int
104open_descriptor(int descriptor, const char* name, int flags, int mode = 0)
105{ return descriptors.open(descriptor, name, flags, mode); }
106
107inline void
108release_descriptor(int descriptor, bool permanent)
109{ descriptors.release(descriptor, permanent); }
110
111inline void
112close_all_descriptors()
113{ descriptors.close_all(); }
114
115} // End namespace gold.
116
117#endif // !defined(GOLD_DESCRIPTORS_H)
118