net/SocketAddress: add method GetLocalPath()

src/net/AllocatedSocketAddress.hxx

@@ -147,6 +147,14 @@ public:
 	StringView GetLocalRaw() const noexcept;
 
 	/**
+	 * @see SocketAddress::GetLocalPath()
+	 */
+	gcc_pure
+	const char *GetLocalPath() const noexcept {
+		return ((SocketAddress)*this).GetLocalPath();
+	}
+
+	/**
 	 * Make this a "local" address (UNIX domain socket).  If the path
 	 * begins with a '@', then the rest specifies an "abstract" local
 	 * address.

src/net/SocketAddress.cxx

 /*
- * Copyright (C) 2012-2017 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2012-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -73,6 +73,21 @@ SocketAddress::GetLocalRaw() const noexcept
 	return {path, size - header_size};
 }
 
+const char *
+SocketAddress::GetLocalPath() const noexcept
+{
+	const auto raw = GetLocalRaw();
+	return !raw.empty() &&
+		/* must be an absolute path */
+		raw.front() == '/' &&
+		/* must be null-terminated */
+		raw.back() == 0 &&
+		/* there must not be any other null byte */
+		memchr(raw.data, 0, raw.size - 1) == nullptr
+		? raw.data
+		: nullptr;
+}
+
 #endif
 
 #ifdef HAVE_TCP

src/net/SocketAddress.hxx

 /*
- * Copyright (C) 2012-2017 Max Kellermann <max.kellermann@gmail.com>
+ * Copyright 2012-2019 Max Kellermann <max.kellermann@gmail.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -106,6 +106,13 @@ public:
 	 */
 	gcc_pure
 	StringView GetLocalRaw() const noexcept;
+
+	/**
+	 * Returns the local socket path or nullptr if not applicable
+	 * (or if the path is corrupt).
+	 */
+	gcc_pure
+	const char *GetLocalPath() const noexcept;
 #endif
 
 #ifdef HAVE_TCP