gold/descriptors.h

   1 // descriptors.h -- manage file descriptors for gold   -*- C++ -*-
   2
   3 // Copyright 2008, 2009 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 namespace gold
  29 {
  30
  31 class Lock;
  32
  33 // This class manages file descriptors for gold.
  34
  35 class 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  private:
  60   // Information kept for a descriptor.
  61   struct Open_descriptor
  62   {
  63     // File name currently associated with descriptor.  This is empty
  64     // if none.
  65     const char* name;
  66     // Index of next descriptor on stack of released descriptors.
  67     int stack_next;
  68     // Whether the descriptor is currently in use.
  69     bool inuse;
  70     // Whether this is a write descriptor.
  71     bool is_write;
  72   };
  73
  74   bool
  75   close_some_descriptor();
  76
  77   // We need to lock before accessing any fields.
  78   Lock* lock_;
  79   // Information for descriptors.
  80   std::vector<Open_descriptor> open_descriptors_;
  81   // Top of stack.
  82   int stack_top_;
  83   // The current number of file descriptors open.
  84   int current_;
  85   // The maximum number of file descriptors we open.
  86   int limit_;
  87 };
  88
  89 // File descriptors are a centralized data structure, and we use a
  90 // global variable rather than passing the data structure into every
  91 // routine that does file I/O.
  92
  93 extern Descriptors descriptors;
  94
  95 inline int
  96 open_descriptor(int descriptor, const char* name, int flags, int mode = 0)
  97 { return descriptors.open(descriptor, name, flags, mode); }
  98
  99 inline void
 100 release_descriptor(int descriptor, bool permanent)
 101 { descriptors.release(descriptor, permanent); }
 102
 103 } // End namespace gold.
 104
 105 #endif // !defined(GOLD_DESCRIPTORS_H)