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      1 // Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef BASE_FILE_DESCRIPTOR_POSIX_H_
      6 #define BASE_FILE_DESCRIPTOR_POSIX_H_
      7 
      8 #include "base/files/file.h"
      9 #include "base/files/scoped_file.h"
     10 
     11 namespace base {
     12 
     13 // -----------------------------------------------------------------------------
     14 // We introduct a special structure for file descriptors in order that we are
     15 // able to use template specialisation to special-case their handling.
     16 //
     17 // IMPORTANT: This is primarily intended for use when sending file descriptors
     18 // over IPC. Even if |auto_close| is true, base::FileDescriptor does NOT close()
     19 // |fd| when going out of scope. Instead, a consumer of a base::FileDescriptor
     20 // must invoke close() on |fd| if |auto_close| is true.
     21 //
     22 // In the case of IPC, the the IPC subsystem knows to close() |fd| after sending
     23 // a message that contains a base::FileDescriptor if auto_close == true. On the
     24 // other end, the receiver must make sure to close() |fd| after it has finished
     25 // processing the IPC message. See the IPC::ParamTraits<> specialization in
     26 // ipc/ipc_message_utils.h for all the details.
     27 // -----------------------------------------------------------------------------
     28 struct FileDescriptor {
     29   FileDescriptor() : fd(-1), auto_close(false) {}
     30 
     31   FileDescriptor(int ifd, bool iauto_close) : fd(ifd), auto_close(iauto_close) {
     32   }
     33 
     34   FileDescriptor(File file) : fd(file.TakePlatformFile()), auto_close(true) {}
     35   explicit FileDescriptor(ScopedFD fd) : fd(fd.release()), auto_close(true) {}
     36 
     37   bool operator==(const FileDescriptor& other) const {
     38     return (fd == other.fd && auto_close == other.auto_close);
     39   }
     40 
     41   bool operator!=(const FileDescriptor& other) const {
     42     return !operator==(other);
     43   }
     44 
     45   // A comparison operator so that we can use these as keys in a std::map.
     46   bool operator<(const FileDescriptor& other) const {
     47     return other.fd < fd;
     48   }
     49 
     50   int fd;
     51   // If true, this file descriptor should be closed after it has been used. For
     52   // example an IPC system might interpret this flag as indicating that the
     53   // file descriptor it has been given should be closed after use.
     54   bool auto_close;
     55 };
     56 
     57 }  // namespace base
     58 
     59 #endif  // BASE_FILE_DESCRIPTOR_POSIX_H_
     60