fs/Traits: add IsAbsolute(string_view)

src/command/StorageCommands.cxx

@@ -94,7 +94,7 @@ print_storage_uri(Client &client, Response &r, const Storage &storage)
 	if (uri.empty())
 		return;
 
-	if (PathTraitsUTF8::IsAbsolute(uri.c_str())) {
+	if (PathTraitsUTF8::IsAbsolute(uri)) {
 		/* storage points to local directory */
 
 		if (!client.IsLocal())

src/fs/AllocatedPath.hxx

@@ -337,7 +337,7 @@ public:
 
 	[[gnu::pure]]
 	bool IsAbsolute() const noexcept {
-		return Traits::IsAbsolute(c_str());
+		return Traits::IsAbsolute(value);
 	}
 };
 

src/fs/Traits.hxx

@@ -130,6 +130,15 @@ struct PathTraitsFS {
 		return IsSeparator(*p);
 	}
 
+	[[gnu::pure]]
+	static bool IsAbsolute(string_view p) noexcept {
+#ifdef _WIN32
+		if (IsDrive(p) && IsSeparator(p[2]))
+			return true;
+#endif
+		return !p.empty() && IsSeparator(p.front());
+	}
+
 	[[gnu::pure]] [[gnu::nonnull]]
 	static bool IsSpecialFilename(const_pointer name) noexcept {
 		return (name[0] == '.' && name[1] == 0) ||
@@ -274,6 +283,15 @@ struct PathTraitsUTF8 {
 		return IsSeparator(*p);
 	}
 
+	[[gnu::pure]]
+	static bool IsAbsolute(string_view p) noexcept {
+#ifdef _WIN32
+		if (IsDrive(p) && IsSeparator(p[2]))
+			return true;
+#endif
+		return !p.empty() && IsSeparator(p.front());
+	}
+
 	/**
 	 * Is this any kind of absolute URI? (Unlike IsAbsolute(),
 	 * this includes URIs/URLs with a scheme)