std/os: add File.Str, File.IsDir, File.IsRegular, File.Type

std/os/types.jule

@@ -35,8 +35,51 @@ const ModeType = ModeDir | ModeSymlink | ModeNamedPipe | ModeSocket | ModeDevice
 const ModePerm = 0777
 
 impl FileMode {
+	fn Str(self): str {
+		const s = "dalTLDpSugct?"
+		let mut buf: [32]byte // Mode is uint32.
+		mut w := 0
+		for i, c in s {
+			if self&(1<<uint(32-1-i)) != 0 {
+				buf[w] = byte(c)
+				w++
+			}
+		}
+		if w == 0 {
+			buf[w] = '-'
+			w++
+		}
+		const rwx = "rwxrwxrwx"
+		for i, c in rwx {
+			if self&(1<<uint(9-1-i)) != 0 {
+				buf[w] = byte(c)
+			} else {
+				buf[w] = '-'
+			}
+			w++
+		}
+		ret str(buf[:w])
+	}
+
+	// Reports whether self describes a directory.
+	// That is, it tests for the [ModeDir] bit being set in self.
+	fn IsDir(self): bool {
+		ret self&ModeDir != 0
+	}
+
+	// Reports whether self describes a regular file.
+	// That is, it tests that no mode type bits are set.
+	fn IsRegular(self): bool {
+		ret self&ModeType == 0
+	}
+
 	// Returns the Unix permission bits in self (self & [ModePerm]).
 	fn Perm(self): FileMode {
 		ret self & ModePerm
 	}
+
+	// Returns type bits in self (self & [ModeType]).
+	fn Type(self): FileMode {
+		ret self & ModeType
+	}
 }