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// Copyright (c) 2006-2009 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef CHROME_COMMON_FILE_DESCRIPTOR_SET_POSIX_H_
#define CHROME_COMMON_FILE_DESCRIPTOR_SET_POSIX_H_
#include <vector>
#include "base/basictypes.h"
#include "base/file_descriptor_posix.h"
#include "base/ref_counted.h"
// -----------------------------------------------------------------------------
// A FileDescriptorSet is an ordered set of POSIX file descriptors. These are
// associated with IPC messages so that descriptors can be transmitted over a
// UNIX domain socket.
// -----------------------------------------------------------------------------
class FileDescriptorSet : public base::RefCountedThreadSafe<FileDescriptorSet> {
public:
FileDescriptorSet();
~FileDescriptorSet();
// This is the maximum number of descriptors per message. We need to know this
// because the control message kernel interface has to be given a buffer which
// is large enough to store all the descriptor numbers. Otherwise the kernel
// tells us that it truncated the control data and the extra descriptors are
// lost.
//
// In debugging mode, it's a fatal error to try and add more than this number
// of descriptors to a FileDescriptorSet.
enum {
MAX_DESCRIPTORS_PER_MESSAGE = 4,
};
// ---------------------------------------------------------------------------
// Interfaces for building during message serialisation...
// Add a descriptor to the end of the set. Returns false iff the set is full.
bool Add(int fd);
// Add a descriptor to the end of the set and automatically close it after
// transmission. Returns false iff the set is full.
bool AddAndAutoClose(int fd);
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for accessing during message deserialisation...
// Return the number of descriptors
unsigned size() const { return descriptors_.size(); }
// Return true if no unconsumed descriptors remain
bool empty() const { return descriptors_.empty(); }
// Fetch the nth descriptor from the beginning of the set. Code using this
// /must/ access the descriptors in order, except that it may wrap from the
// end to index 0 again.
//
// This interface is designed for the deserialising code as it doesn't
// support close flags.
// returns: file descriptor, or -1 on error
int GetDescriptorAt(unsigned n) const;
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for transmission...
// Fill an array with file descriptors without 'consuming' them. CommitAll
// must be called after these descriptors have been transmitted.
// buffer: (output) a buffer of, at least, size() integers.
void GetDescriptors(int* buffer) const;
// This must be called after transmitting the descriptors returned by
// GetDescriptors. It marks all the descriptors as consumed and closes those
// which are auto-close.
void CommitAll();
// ---------------------------------------------------------------------------
// ---------------------------------------------------------------------------
// Interfaces for receiving...
// Set the contents of the set from the given buffer. This set must be empty
// before calling. The auto-close flag is set on all the descriptors so that
// unconsumed descriptors are closed on destruction.
void SetDescriptors(const int* buffer, unsigned count);
// ---------------------------------------------------------------------------
private:
// A vector of descriptors and close flags. If this message is sent, then
// these descriptors are sent as control data. After sending, any descriptors
// with a true flag are closed. If this message has been received, then these
// are the descriptors which were received and all close flags are true.
std::vector<base::FileDescriptor> descriptors_;
// This contains the index of the next descriptor which should be consumed.
// It's used in a couple of ways. Firstly, at destruction we can check that
// all the descriptors have been read (with GetNthDescriptor). Secondly, we
// can check that they are read in order.
mutable unsigned consumed_descriptor_highwater_;
DISALLOW_COPY_AND_ASSIGN(FileDescriptorSet);
};
#endif // CHROME_COMMON_FILE_DESCRIPTOR_SET_POSIX_H_
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