1 // Copyright (c) 2012 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.
5 #ifndef BASE_SYNC_SOCKET_H_
6 #define BASE_SYNC_SOCKET_H_
8 // A socket abstraction used for sending and receiving plain
9 // data. Because the receiving is blocking, they can be used to perform
10 // rudimentary cross-process synchronization with low latency.
14 #include "base/base_export.h"
15 #include "base/compiler_specific.h"
16 #include "base/macros.h"
17 #include "base/process/process_handle.h"
18 #include "base/synchronization/waitable_event.h"
19 #include "base/time/time.h"
20 #include "build/build_config.h"
25 #include <sys/types.h>
27 #if defined(OS_POSIX) || defined(OS_FUCHSIA)
28 #include "base/file_descriptor_posix.h"
33 class BASE_EXPORT SyncSocket {
36 typedef HANDLE Handle;
37 typedef Handle TransitDescriptor;
38 #elif defined(OS_POSIX) || defined(OS_FUCHSIA)
40 typedef FileDescriptor TransitDescriptor;
42 static const Handle kInvalidHandle;
46 // Creates a SyncSocket from a Handle. Used in transport.
47 explicit SyncSocket(Handle handle) : handle_(handle) {}
48 virtual ~SyncSocket();
50 // Initializes and connects a pair of sockets.
51 // |socket_a| and |socket_b| must not hold a valid handle. Upon successful
52 // return, the sockets will both be valid and connected.
53 static bool CreatePair(SyncSocket* socket_a, SyncSocket* socket_b);
55 // Returns |Handle| wrapped in a |TransitDescriptor|.
56 static Handle UnwrapHandle(const TransitDescriptor& descriptor);
58 // Prepares a |TransitDescriptor| which wraps |Handle| used for transit.
59 // This is used to prepare the underlying shared resource before passing back
60 // the handle to be used by the peer process.
61 bool PrepareTransitDescriptor(ProcessHandle peer_process_handle,
62 TransitDescriptor* descriptor);
64 // Closes the SyncSocket. Returns true on success, false on failure.
67 // Sends the message to the remote peer of the SyncSocket.
68 // Note it is not safe to send messages from the same socket handle by
69 // multiple threads simultaneously.
70 // buffer is a pointer to the data to send.
71 // length is the length of the data to send (must be non-zero).
72 // Returns the number of bytes sent, or 0 upon failure.
73 virtual size_t Send(const void* buffer, size_t length);
75 // Receives a message from an SyncSocket.
76 // buffer is a pointer to the buffer to receive data.
77 // length is the number of bytes of data to receive (must be non-zero).
78 // Returns the number of bytes received, or 0 upon failure.
79 virtual size_t Receive(void* buffer, size_t length);
81 // Same as Receive() but only blocks for data until |timeout| has elapsed or
82 // |buffer| |length| is exhausted. Currently only timeouts less than one
83 // second are allowed. Return the amount of data read.
84 virtual size_t ReceiveWithTimeout(void* buffer,
88 // Returns the number of bytes available. If non-zero, Receive() will not
89 // not block when called.
90 virtual size_t Peek();
92 // Extracts the contained handle. Used for transferring between
94 Handle handle() const { return handle_; }
96 // Extracts and takes ownership of the contained handle.
103 DISALLOW_COPY_AND_ASSIGN(SyncSocket);
106 // Derives from SyncSocket and adds support for shutting down the socket from
107 // another thread while a blocking Receive or Send is being done from the
108 // thread that owns the socket.
109 class BASE_EXPORT CancelableSyncSocket : public SyncSocket {
111 CancelableSyncSocket();
112 explicit CancelableSyncSocket(Handle handle);
113 ~CancelableSyncSocket() override = default;
115 // Initializes a pair of cancelable sockets. See documentation for
116 // SyncSocket::CreatePair for more details.
117 static bool CreatePair(CancelableSyncSocket* socket_a,
118 CancelableSyncSocket* socket_b);
120 // A way to shut down a socket even if another thread is currently performing
121 // a blocking Receive or Send.
125 // Since the Linux and Mac implementations actually use a socket, shutting
126 // them down from another thread is pretty simple - we can just call
127 // shutdown(). However, the Windows implementation relies on named pipes
128 // and there isn't a way to cancel a blocking synchronous Read that is
129 // supported on <Vista. So, for Windows only, we override these
130 // SyncSocket methods in order to support shutting down the 'socket'.
131 bool Close() override;
132 size_t Receive(void* buffer, size_t length) override;
133 size_t ReceiveWithTimeout(void* buffer,
135 TimeDelta timeout) override;
138 // Send() is overridden to catch cases where the remote end is not responding
139 // and we fill the local socket buffer. When the buffer is full, this
140 // implementation of Send() will not block indefinitely as
141 // SyncSocket::Send will, but instead return 0, as no bytes could be sent.
142 // Note that the socket will not be closed in this case.
143 size_t Send(const void* buffer, size_t length) override;
147 WaitableEvent shutdown_event_;
148 WaitableEvent file_operation_;
150 DISALLOW_COPY_AND_ASSIGN(CancelableSyncSocket);
153 #if defined(OS_WIN) && !defined(COMPONENT_BUILD)
154 // TODO(cpu): remove this once chrome is split in two dlls.
155 __declspec(selectany)
156 const SyncSocket::Handle SyncSocket::kInvalidHandle = INVALID_HANDLE_VALUE;
161 #endif // BASE_SYNC_SOCKET_H_