Split out socket.hh from unix-domain-socket.hh

There are other types of sockets.

src/libutil/include/nix/util/meson.build

@@ -65,6 +65,7 @@ headers = files(
   'signals.hh',
   'signature/local-keys.hh',
   'signature/signer.hh',
+  'socket.hh',
   'sort.hh',
   'source-accessor.hh',
   'source-path.hh',

src/libutil/include/nix/util/socket.hh

@@ -0,0 +1,61 @@
+#pragma once
+///@file
+
+#include "nix/util/file-descriptor.hh"
+
+#ifdef _WIN32
+#  include <winsock2.h>
+#endif
+
+namespace nix {
+
+/**
+ * Often we want to use `Descriptor`, but Windows makes a slightly
+ * stronger file descriptor vs socket distinction, at least at the level
+ * of C types.
+ */
+using Socket =
+#ifdef _WIN32
+    SOCKET
+#else
+    int
+#endif
+    ;
+
+#ifdef _WIN32
+/**
+ * Windows gives this a different name
+ */
+#  define SHUT_WR SD_SEND
+#  define SHUT_RDWR SD_BOTH
+#endif
+
+/**
+ * Convert a `Descriptor` to a `Socket`
+ *
+ * This is a no-op except on Windows.
+ */
+static inline Socket toSocket(Descriptor fd)
+{
+#ifdef _WIN32
+    return reinterpret_cast<Socket>(fd);
+#else
+    return fd;
+#endif
+}
+
+/**
+ * Convert a `Socket` to a `Descriptor`
+ *
+ * This is a no-op except on Windows.
+ */
+static inline Descriptor fromSocket(Socket fd)
+{
+#ifdef _WIN32
+    return reinterpret_cast<Descriptor>(fd);
+#else
+    return fd;
+#endif
+}
+
+} // namespace nix

src/libutil/include/nix/util/unix-domain-socket.hh

@@ -3,10 +3,8 @@
 
 #include "nix/util/types.hh"
 #include "nix/util/file-descriptor.hh"
+#include "nix/util/socket.hh"
 
-#ifdef _WIN32
-#  include <winsock2.h>
-#endif
 #include <unistd.h>
 
 #include <filesystem>
@@ -23,55 +21,6 @@ AutoCloseFD createUnixDomainSocket();
  */
 AutoCloseFD createUnixDomainSocket(const Path & path, mode_t mode);
 
-/**
- * Often we want to use `Descriptor`, but Windows makes a slightly
- * stronger file descriptor vs socket distinction, at least at the level
- * of C types.
- */
-using Socket =
-#ifdef _WIN32
-    SOCKET
-#else
-    int
-#endif
-    ;
-
-#ifdef _WIN32
-/**
- * Windows gives this a different name
- */
-#  define SHUT_WR SD_SEND
-#  define SHUT_RDWR SD_BOTH
-#endif
-
-/**
- * Convert a `Socket` to a `Descriptor`
- *
- * This is a no-op except on Windows.
- */
-static inline Socket toSocket(Descriptor fd)
-{
-#ifdef _WIN32
-    return reinterpret_cast<Socket>(fd);
-#else
-    return fd;
-#endif
-}
-
-/**
- * Convert a `Socket` to a `Descriptor`
- *
- * This is a no-op except on Windows.
- */
-static inline Descriptor fromSocket(Socket fd)
-{
-#ifdef _WIN32
-    return reinterpret_cast<Descriptor>(fd);
-#else
-    return fd;
-#endif
-}
-
 /**
  * Bind a Unix domain socket to a path.
  */