libcutils: share Windows networking code.

This CL moves Windows networking code from fastboot to libcutils so
that it can be shared with other host programs such as adb.

Not all libcutils networking functions have been implemented for
Windows, just those necessary for fastboot. In the next CL I will do
the same for adb, adding any additional required functions.

Unit tests have also been added to test the functions using a loopback
connection.

Bug: http://b/26236380.
Change-Id: Ibc51a67030fe69a04c23512eefa9d19b055c7c12
diff --git a/libcutils/sockets_windows.c b/libcutils/sockets_windows.c
new file mode 100644
index 0000000..92ccf88
--- /dev/null
+++ b/libcutils/sockets_windows.c
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <cutils/sockets.h>
+
+// https://msdn.microsoft.com/en-us/library/windows/desktop/ms741549(v=vs.85).aspx
+// claims WSACleanup() should be called before program exit, but general
+// consensus seems to be that it hasn't actually been necessary for a long time,
+// likely since Windows 3.1. Additionally, trying to properly use WSACleanup()
+// can be extremely tricky and cause deadlock when using threads or atexit().
+//
+// Both adb (1) and Chrome (2) purposefully avoid WSACleanup() with no issues.
+// (1) https://android.googlesource.com/platform/system/core.git/+/master/adb/sysdeps_win32.cpp
+// (2) https://code.google.com/p/chromium/codesearch#chromium/src/net/base/winsock_init.cc
+bool initialize_windows_sockets() {
+    // There's no harm in calling WSAStartup() multiple times but no benefit
+    // either, we may as well skip it after the first.
+    static bool init_success = false;
+
+    if (!init_success) {
+        WSADATA wsaData;
+        init_success = (WSAStartup(MAKEWORD(2, 2), &wsaData) == 0);
+    }
+
+    return init_success;
+}
+
+int socket_close(cutils_socket_t sock) {
+    return closesocket(sock);
+}