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)
+      : name_(name), fd_(-1) { }
+
+  virtual ~MultiProcessLockLinux() {
+    if (fd_ != -1) {
+      Unlock();
+    }
+  }
+
+  virtual bool TryLock() {
+    if (fd_ != -1) {
+      DLOG(ERROR) << "MultiProcessLock is already locked - " << name_;
+      return true;
+    }
+
+    if (name_.length() > MULTI_PROCESS_LOCK_NAME_MAX_LEN) {
+      LOG(ERROR) << "Socket name too long - " << name_;
+      return false;
+    }
+
+    struct sockaddr_un address;
+    memset(&address, 0, sizeof(address));

[Mark Mentovai, 2010/11/15 23:42:55]

Or you could have just written
    struct sockaddr_un address = {0};

[dmac, 2010/11/15 23:55:24]

I usually go with the memset just in case someone compiles with pedantic on.

+    memcpy(&address.sun_path[1], name_.data(), name_.length());
+
+    // Must set the first character of the path to something non-zero
+    // before we call SUN_LEN which depends on strcpy working.
+    address.sun_path[0] = '@';
+    size_t length = SUN_LEN(&address);
+
+    // Reset the first character of the path back to zero so that
+    // bind returns an abstract name socket.
+    address.sun_path[0] = 0;
+    address.sun_family = AF_LOCAL;
+
+    int socket_fd = socket(AF_LOCAL, SOCK_STREAM, 0);
+    if (socket_fd < 0) {
+      PLOG(ERROR) << "Couldn't create socket - " << name_;
+      return false;
+    }
+
+    if (bind(socket_fd,
+             reinterpret_cast<sockaddr *>(&address),
+             length) == 0) {
+      fd_ = socket_fd;
+      return true;
+    } else {
+      NOTREACHED() << "Couldn't bind socket - " << address.sun_path;
+      HANDLE_EINTR(close(socket_fd));
+      return false;
+    }
+  }
+
+  virtual void Unlock() {
+    if (fd_ == -1) {
+      DLOG(ERROR) << "Over-unlocked MultiProcessLock - " << name_;
+      return;
+    }
+    HANDLE_EINTR(close(fd_));
+    fd_ = -1;
+  }
+
+ private:
+  std::string name_;
+  int fd_;
+  DISALLOW_COPY_AND_ASSIGN(MultiProcessLockLinux);
+};
+
+MultiProcessLock* MultiProcessLock::Create(const std::string &name) {
+  return new MultiProcessLockLinux(name);
+}