gold/descriptors.h

   1 // descriptors.h -- manage file descriptors for gold   -*- C++ -*-
   2
   3 // Copyright 2008 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   // Claim the file descriptor DESCRIPTOR for a plugin.  This effectively
  60   // removes the descriptor from the pool of linker-managed descriptors,
  61   // as the plugin will assume responsibility for closing it.
  62   void
  63   claim_for_plugin(int descriptor);
  64
  65  private:
  66   // Information kept for a descriptor.
  67   struct Open_descriptor
  68   {
  69     // File name currently associated with descriptor.  This is empty
  70     // if none.
  71     const char* name;
  72     // Index of next descriptor on stack of released descriptors.
  73     int stack_next;
  74     // Whether the descriptor is currently in use.
  75     bool inuse;
  76     // Whether this is a write descriptor.
  77     bool is_write;
  78     // Whether the descriptor has been claimed for a plugin.
  79     bool is_claimed;
  80   };
  81
  82   bool
  83   close_some_descriptor();
  84
  85   // We need to lock before accessing any fields.
  86   Lock* 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
 101 extern Descriptors descriptors;
 102
 103 inline int
 104 open_descriptor(int descriptor, const char* name, int flags, int mode = 0)
 105 { return descriptors.open(descriptor, name, flags, mode); }
 106
 107 inline void
 108 release_descriptor(int descriptor, bool permanent)
 109 { descriptors.release(descriptor, permanent); }
 110
 111 inline void
 112 claim_descriptor_for_plugin(int descriptor)
 113 { descriptors.claim_for_plugin(descriptor); }
 114
 115 } // End namespace gold.
 116
 117 #endif // !defined(GOLD_DESCRIPTORS_H)