1 files changed, 57 insertions, 0 deletions
diff --git a/libgo/go/os/user/listgroups_unix.go b/libgo/go/os/user/listgroups_unix.go
new file mode 100644
index 000000000000..8b2b13d563ff
--- /dev/null
+++ b/libgo/go/os/user/listgroups_unix.go
@@ -0,0 +1,57 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build dragonfly darwin freebsd !android,linux netbsd openbsd
+
+package user
+
+import (
+	"fmt"
+	"strconv"
+	"syscall"
+)
+
+/*
+#include <unistd.h>
+#include <sys/types.h>
+#include <stdlib.h>
+*/
+
+func listGroups(u *User) ([]string, error) {
+	ug, err := strconv.Atoi(u.Gid)
+	if err != nil {
+		return nil, fmt.Errorf("user: list groups for %s: invalid gid %q", u.Username, u.Gid)
+	}
+	userGID := syscall.Gid_t(ug)
+	nameC, err := syscall.BytePtrFromString(u.Username)
+	if err != nil {
+		return nil, fmt.Errorf("user: invalid user name %q: %v", strconv.Quote(u.Username), err)
+	}
+
+	n := int32(256)
+	gidsC := make([]syscall.Gid_t, n)
+	syscall.Entersyscall()
+	rv := libc_getgrouplist(nameC, userGID, &gidsC[0], &n)
+	syscall.Exitsyscall()
+	if rv == -1 {
+		// More than initial buffer, but now n contains the correct size.
+		const maxGroups = 2048
+		if n > maxGroups {
+			return nil, fmt.Errorf("user: list groups for %s: member of more than %d groups", u.Username, maxGroups)
+		}
+		gidsC = make([]syscall.Gid_t, n)
+		syscall.Entersyscall()
+		rv := libc_getgrouplist(nameC, userGID, &gidsC[0], &n)
+		syscall.Exitsyscall()
+		if rv == -1 {
+			return nil, fmt.Errorf("user: list groups for %s failed (changed groups?)", u.Username)
+		}
+	}
+	gidsC = gidsC[:n]
+	gids := make([]string, 0, n)
+	for _, g := range gidsC[:n] {
+		gids = append(gids, strconv.Itoa(int(g)))
+	}
+	return gids, nil
+}