win32: share code to find root prefix of path

Move unc_root_len() from ash to mingw32.c and use it in the new
function root_len(), which can be used in make_directory().

This reduces changes to upstream code and saves a few bytes.

1 files changed, 35 insertions, 0 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 0206f6dca..3ee1a2496 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -1609,3 +1609,38 @@ void hide_console(void)
         }
 }
 #endif
+
+#define is_path_sep(x) ((x) == '/' || (x) == '\\')
+#define is_unc_path(x) (is_path_sep(x[0]) && is_path_sep(x[1]))
+
+/* Return the length of the root of a UNC path, i.e. the '//host/share'
+ * component, or 0 if the path doesn't look like that. */
+int unc_root_len(const char *dir)
+{
+        const char *s = dir + 2;
+        int len;
+
+        if (!is_unc_path(dir))
+                return 0;
+        len = strcspn(s, "/\\");
+        if (len == 0)
+                return 0;
+        s += len + 1;
+        len = strcspn(s, "/\\");
+        if (len == 0)
+                return 0;
+        s += len;
+
+        return s - dir;
+}
+
+/* Return the length of the root of a path, i.e. either the drive or
+ * UNC '//host/share', or 0 if the path doesn't look like that. */
+int root_len(const char *path)
+{
+        if (path == NULL)
+                return 0;
+        if (isalpha(*path) && path[1] == ':')
+                return 2;
+        return unc_root_len(path);
+}