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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)