Add multi_process_lock to chrome/common

chrome/common/multi_process_lock_linux.cc

+// Copyright (c) 2010 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.
+
+#include "chrome/common/multi_process_lock.h"
+
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+
+#include "base/eintr_wrapper.h"
+#include "base/logging.h"
+
+class MultiProcessLockLinux : public MultiProcessLock {
+ public:
+  explicit MultiProcessLockLinux(const std::string& name)
+      : MultiProcessLock(name), fd_(-1) { }
+
+  virtual ~MultiProcessLockLinux() { Unlock(); }
+
+  virtual bool TryLock() {
+    struct sockaddr_un address;
+    // +2 because: 1 for terminator, and 1 for \0 at the front that makes

[agl, 2010/11/11 21:50:53]

terminator? These aren't NUL terminated names.

[dmac, 2010/11/11 23:33:02]

agl, as far as I know you either have to NUL terminate the name OR pass in an
exact length down in bind. How does bind know the length of the string to use as
the name if it isn't NUL terminated or given an exact name? I did some research
here and I'm startled by the fact that no one seems to be able to agree how bind
is to be called in this case.

+    // this an abstract name port.
+    if (name_.length() + 2 > sizeof(address.sun_path)) {
+      NOTREACHED() << "Socket name too long";

[Mark Mentovai, 2010/11/11 22:08:27]

name_, and thus its length, is fully in the caller’s control. This isn’t really
NOTREACHED, it’s a normal failure case that you hope to never hit.

[dmac, 2010/11/11 23:33:02]

Changed, and test added.

+      return false;
+    }
+    memset(&address, 0, sizeof(address));
+    memcpy(&address.sun_path[1], name_.data(), name_.length());
+    address.sun_family = AF_LOCAL;
+    int socket_fd = socket(AF_LOCAL, SOCK_STREAM, 0);
+    if (socket_fd < 0) {
+      PLOG(ERROR) << "Couldn't create socket";
+      return false;
+    }
+    if (bind(socket_fd,
+             reinterpret_cast<sockaddr *>(&address),
+             sizeof(address)) == 0) {
+      fd_ = socket_fd;
+      return true;
+    } else {
+      NOTREACHED() << "Couldn't bind socket to " << address.sun_path;
+      HANDLE_EINTR(close(socket_fd));
+      return false;
+    }
+  }
+
+  virtual void Unlock() {
+    if (fd_ != -1) {
+      HANDLE_EINTR(close(fd_));
+      fd_ = -1;
+    }
+  }
+
+ private:
+  int fd_;
+  DISALLOW_COPY_AND_ASSIGN(MultiProcessLockLinux);
+};
+
+MultiProcessLock* MultiProcessLock::Create(const std::string &name) {
+  return new MultiProcessLockLinux(name);
+}