From a119ec7c824da4a618cb3f4c6e3557c38381b674 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 9 Aug 2017 19:01:18 +0200
Subject: [PATCH] util-lib: add a new skip_dev_prefix() helper

This new helper removes a leading /dev if there is one. We have code
doing this all over the place, let's unify this, and correct it while
we are at it, by using path_startswith() rather than startswith() to
drop the prefix.
---
 src/basic/path-util.h     | 10 ++++++++++
 src/basic/terminal-util.c | 15 ++++-----------
 src/core/execute.c        |  3 +--
 src/test/test-path-util.c | 16 ++++++++++++++++
 4 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/src/basic/path-util.h b/src/basic/path-util.h
index 26f165f..ea00955 100644
--- a/src/basic/path-util.h
+++ b/src/basic/path-util.h
@@ -143,3 +143,13 @@ bool is_deviceallow_pattern(const char *path);
 int systemd_installation_has_version(const char *root, unsigned minimal_version);
 
 bool dot_or_dot_dot(const char *path);
+
+static inline const char *skip_dev_prefix(const char *p) {
+        const char *e;
+
+        /* Drop any /dev prefix if there is any */
+
+        e = path_startswith(p, "/dev/");
+
+        return e ?: p;
+}
diff --git a/src/basic/terminal-util.c b/src/basic/terminal-util.c
index 8a0419d..c570c2e 100644
--- a/src/basic/terminal-util.c
+++ b/src/basic/terminal-util.c
@@ -649,10 +649,7 @@ bool tty_is_vc(const char *tty) {
 bool tty_is_console(const char *tty) {
         assert(tty);
 
-        if (startswith(tty, "/dev/"))
-                tty += 5;
-
-        return streq(tty, "console");
+        return streq(skip_dev_prefix(tty), "console");
 }
 
 int vtnr_from_tty(const char *tty) {
@@ -660,8 +657,7 @@ int vtnr_from_tty(const char *tty) {
 
         assert(tty);
 
-        if (startswith(tty, "/dev/"))
-                tty += 5;
+        tty = skip_dev_prefix(tty);
 
         if (!startswith(tty, "tty") )
                 return -EINVAL;
@@ -775,8 +771,7 @@ bool tty_is_vc_resolve(const char *tty) {
 
         assert(tty);
 
-        if (startswith(tty, "/dev/"))
-                tty += 5;
+        tty = skip_dev_prefix(tty);
 
         if (streq(tty, "console")) {
                 tty = resolve_dev_console(&active);
@@ -918,11 +913,9 @@ int getttyname_malloc(int fd, char **ret) {
 
                 r = ttyname_r(fd, path, sizeof(path));
                 if (r == 0) {
-                        const char *p;
                         char *c;
 
-                        p = startswith(path, "/dev/");
-                        c = strdup(p ?: path);
+                        c = strdup(skip_dev_prefix(path));
                         if (!c)
                                 return -ENOMEM;
 
diff --git a/src/core/execute.c b/src/core/execute.c
index 55f9aab..21488a0 100644
--- a/src/core/execute.c
+++ b/src/core/execute.c
@@ -3400,8 +3400,7 @@ static bool tty_may_match_dev_console(const char *tty) {
         if (!tty)
                 return true;
 
-        if (startswith(tty, "/dev/"))
-                tty += 5;
+        tty = skip_dev_prefix(tty);
 
         /* trivial identity? */
         if (streq(tty, "console"))
diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c
index e564424..e708d6e 100644
--- a/src/test/test-path-util.c
+++ b/src/test/test-path-util.c
@@ -588,6 +588,21 @@ static void test_systemd_installation_has_version(const char *path) {
         }
 }
 
+static void test_skip_dev_prefix(void) {
+
+        assert_se(streq(skip_dev_prefix("/"), "/"));
+        assert_se(streq(skip_dev_prefix("/dev"), ""));
+        assert_se(streq(skip_dev_prefix("/dev/"), ""));
+        assert_se(streq(skip_dev_prefix("/dev/foo"), "foo"));
+        assert_se(streq(skip_dev_prefix("/dev/foo/bar"), "foo/bar"));
+        assert_se(streq(skip_dev_prefix("//dev"), ""));
+        assert_se(streq(skip_dev_prefix("//dev//"), ""));
+        assert_se(streq(skip_dev_prefix("/dev///foo"), "foo"));
+        assert_se(streq(skip_dev_prefix("///dev///foo///bar"), "foo///bar"));
+        assert_se(streq(skip_dev_prefix("//foo"), "//foo"));
+        assert_se(streq(skip_dev_prefix("foo"), "foo"));
+}
+
 int main(int argc, char **argv) {
         log_set_max_level(LOG_DEBUG);
         log_parse_environment();
@@ -607,6 +622,7 @@ int main(int argc, char **argv) {
         test_file_in_same_dir();
         test_filename_is_valid();
         test_hidden_or_backup_file();
+        test_skip_dev_prefix();
 
         test_systemd_installation_has_version(argv[1]); /* NULL is OK */
 
-- 
2.7.4