os: add os.symlink() function

vlib/os/os.v

@@ -23,7 +23,6 @@ struct C.dirent {
 
 fn C.readdir(voidptr) C.dirent
 
-
 pub const (
 	args = []string
 	MAX_PATH = 4096

vlib/os/os_nix.v

@@ -6,6 +6,8 @@ pub const (
 	path_separator = '/'
 )
 
+fn C.symlink(charptr, charptr) int
+
 pub fn init_os_args(argc int, argv &byteptr) []string {
 	mut args := []string
 	for i in 0 .. argc {
@@ -98,3 +100,8 @@ pub fn exec(cmd string) ?Result {
 	}
 }
 
+pub fn symlink(origin, target string) ?bool {
+	res := C.symlink(origin.str, target.str)
+	if res == 0 { return true }
+	return error(get_error_msg(C.errno))
+}

vlib/os/os_test.v

@@ -237,3 +237,14 @@ fn cleanup_leftovers(){
 	os.rm('ex1.txt')
 	os.rm('ex2.txt')
 }
+
+fn test_symlink() {
+  $if windows { return }
+  os.mkdir('symlink') or { panic(err) }
+  os.symlink('symlink', 'symlink2') or { panic(err) }
+  assert os.exists('symlink2')
+
+  // cleanup
+  os.rm('symlink')
+  os.rm('symlink2')
+}

vlib/os/os_windows.v

@@ -285,3 +285,13 @@ pub fn exec(cmd string) ?Result {
 		exit_code: int(exit_code)
 	}
 }
+
+fn C.CreateSymbolicLinkW(&u16, &u16, u32) int
+
+pub fn symlink(origin, target string) ?bool {
+	flags := if os.is_dir(origin) { 1 } else { 0 }
+	if C.CreateSymbolicLinkW(origin.to_wide(), target.to_wide(), u32(flags)) != 0 {
+		return true
+	}
+	return error(get_error_msg(int(C.GetLastError())))
+}