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.

4 files changed, 55 insertions, 10 deletions

diff --git a/include/mingw.h b/include/mingw.h
index 6ace91470..06fb3b289 100644
--- a/include/mingw.h
+++ b/include/mingw.h
@@ -518,6 +518,8 @@ int utimes(const char *file_name, const struct timeval times[2]);
  * MinGW specific
  */
 #define is_dir_sep(c) ((c) == '/' || (c) == '\\')
+#define is_unc_path(x) (strlen(x) > 4 && is_dir_sep(x[0]) && \
+                                                        is_dir_sep(x[1]) && !is_dir_sep(x[2]))
 
 pid_t FAST_FUNC mingw_spawn(char **argv);
 pid_t FAST_FUNC mingw_spawn_detach(char **argv);
@@ -580,3 +582,4 @@ int skip_ansi_emulation(int reset);
 int unix_path(const char *path);
 int has_path(const char *file);
 int is_relative_path(const char *path);
+char *get_last_slash(const char *path);
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;
diff --git a/libbb/xreadlink.c b/libbb/xreadlink.c
index 024ee9047..e6cf90310 100644
--- a/libbb/xreadlink.c
+++ b/libbb/xreadlink.c
@@ -156,7 +156,11 @@ char* FAST_FUNC xmalloc_realpath_coreutils(char *path)
                          * $ realpath symlink
                          * /usr/bin/qwe
                          */
+#if ENABLE_PLATFORM_MINGW32
+                        if (is_relative_path(target)) {
+#else
                         if (target[0] != '/') {
+#endif
                                 /*
                                  * $ ln -s target_does_not_exist symlink
                                  * $ readlink -f symlink
@@ -175,6 +179,35 @@ char* FAST_FUNC xmalloc_realpath_coreutils(char *path)
                         return buf;
                 }
 
+#if ENABLE_PLATFORM_MINGW32
+                /* ignore leading and trailing slashes */
+                /* but keep leading slashes of UNC path */
+                if (!is_unc_path(path)) {
+                        while (is_dir_sep(path[0]) && is_dir_sep(path[1]))
+                                ++path;
+                }
+                i = strlen(path) - 1;
+                while (i > 0 && is_dir_sep(path[i]))
+                        i--;
+                c = path[i + 1];
+                path[i + 1] = '\0';
+
+                last_slash = get_last_slash(path);
+                if (last_slash == path + root_len(path))
+                        buf = xstrdup(path);
+                else if (last_slash) {
+                        char c2 = *last_slash;
+                        *last_slash = '\0';
+                        buf = xmalloc_realpath(path);
+                        *last_slash++ = c2;
+                        if (buf) {
+                                unsigned len = strlen(buf);
+                                buf = xrealloc(buf, len + strlen(last_slash) + 2);
+                                buf[len++] = c2;
+                                strcpy(buf + len, last_slash);
+                        }
+                }
+#else
                 /* ignore leading and trailing slashes */
                 while (path[0] == '/' && path[1] == '/')
                         ++path;
@@ -198,6 +231,7 @@ char* FAST_FUNC xmalloc_realpath_coreutils(char *path)
                                 strcpy(buf + len, last_slash);
                         }
                 }
+#endif
                 path[i + 1] = c;
         }
 
diff --git a/win32/mingw.c b/win32/mingw.c
index fa68ea608..d4855a7e7 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -64,6 +64,8 @@ int err_win_to_posix(void)
         case ERROR_BAD_FORMAT: error = ENOEXEC; break;
         case ERROR_BAD_LENGTH: error = EINVAL; break;
         case ERROR_BAD_PATHNAME: error = ENOENT; break;
+        case ERROR_BAD_NET_NAME: error = ENOENT; break;
+        case ERROR_BAD_NETPATH: error = ENOENT; break;
         case ERROR_BAD_PIPE: error = EPIPE; break;
         case ERROR_BAD_UNIT: error = ENODEV; break;
         case ERROR_BAD_USERNAME: error = EINVAL; break;
@@ -1877,9 +1879,6 @@ void hide_console(void)
 }
 #endif
 
-#define is_unc_path(x) (strlen(x) > 4 && is_dir_sep(x[0]) && \
-                                                        is_dir_sep(x[1]) && !is_dir_sep(x[2]))
-
 /* 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)