realpath: improved support for Windows paths

Upstream commit 94eb1c4dc (libbb: better coreutils compatibility
for realpath) made some changes to xmalloc_realpath_coreutils().
This now needs to be updated to handle Windows paths.

- Expose the macro is_unc_path() and part of the recent change to
  bb_get_last_path_component_nostrip() as a separate funtion,
  get_last_slash();

- Convert a couple of errors relating to network filesystems to
  ENOENT;

- Adjust xmalloc_realpath_coreutils() to handle Windows directory
  separators, relative paths and UNC paths.

1 files changed, 16 insertions, 7 deletions

diff --git a/libbb/get_last_path_component.c b/libbb/get_last_path_component.c
index 06033e139..254aabafd 100644
--- a/libbb/get_last_path_component.c
+++ b/libbb/get_last_path_component.c
@@ -23,6 +23,21 @@ const char* FAST_FUNC bb_basename(const char *name)
         return name;
 }
 
+#if ENABLE_PLATFORM_MINGW32
+char *get_last_slash(const char *path)
+{
+        const char *start = path + root_len(path);
+        char *slash = strrchr(start, '/');
+        char *bslash = strrchr(start, '\\');
+
+        if (slash && bslash)
+                slash = MAX(slash, bslash);
+        else if (!slash)
+                slash = bslash;
+        return slash;
+}
+#endif
+
 /*
  * "/"        -> "/"
  * "abc"      -> "abc"
@@ -33,13 +48,7 @@ char* FAST_FUNC bb_get_last_path_component_nostrip(const char *path)
 {
 #if ENABLE_PLATFORM_MINGW32
         const char *start = path + root_len(path);
-        char *slash = strrchr(start, '/');
-        char *bslash = strrchr(start, '\\');
-
-        if (slash && bslash)
-                slash = MAX(slash, bslash);
-        else if (!slash)
-                slash = bslash;
+        char *slash = get_last_slash(path);
 
         if (!slash && has_dos_drive_prefix(path) && path[2] != '\0')
                 return (char *)path + 2;