Win32: Fix drive root detection with \\?\-style paths

[wimlib] / src / win32_common.c

diff --git a/src/win32_common.c b/src/win32_common.c
index e0d39ac3e1ce8be16b62eba5e84fe070507fe509..e5d6a386f26fd3dfae8595ef3837bfcea580f15b 100644 (file)
--- a/src/win32_common.c
+++ b/src/win32_common.c
@@ -33,6 +33,7 @@
 
 #include "wimlib/assert.h"
 #include "wimlib/error.h"
+#include "wimlib/util.h"
 
 #ifdef ENABLE_ERROR_MESSAGES
 void
@@ -329,6 +330,58 @@ set_errno_from_GetLastError(void)
        errno = win32_error_to_errno(GetLastError());
 }
 
+/* Given a Windows-style path, return the number of characters of the prefix
+ * that specify the path to the root directory of a drive, or return 0 if the
+ * drive is relative (or at least on the current drive, in the case of
+ * absolute-but-not-really-absolute paths like \Windows\System32) */
+static size_t
+win32_path_drive_spec_len(const wchar_t *path)
+{
+       size_t n = 0;
+
+       if (!wcsncmp(path, L"\\\\?\\", 4)) {
+               /* \\?\-prefixed path.  Check for following drive letter and
+                * path separator. */
+               if (path[4] != L'\0' && path[5] == L':' &&
+                   is_any_path_separator(path[6]))
+                       n = 7;
+       } else {
+               /* Not a \\?\-prefixed path.  Check for an initial drive letter
+                * and path separator. */
+               if (path[0] != L'\0' && path[1] == L':' &&
+                   is_any_path_separator(path[2]))
+                       n = 3;
+       }
+       /* Include any additional path separators.*/
+       if (n > 0)
+               while (is_any_path_separator(path[n]))
+                       n++;
+       return n;
+}
+
+bool
+win32_path_is_root_of_drive(const wchar_t *path)
+{
+       size_t drive_spec_len;
+
+       /* Explicit drive letter and path separator? */
+       drive_spec_len = win32_path_drive_spec_len(path);
+       if (drive_spec_len > 0 && path[drive_spec_len] == L'\0')
+               return true;
+
+       /* All path separators? */
+       for (const wchar_t *p = path; *p != L'\0'; p++)
+               if (!is_any_path_separator(*p))
+                       return false;
+       return true;
+
+       /* XXX This function does not handle paths like "c:" where the working
+        * directory on "c:" is actually "c:\", or weird paths like "\.".  But
+        * currently the capture and apply code always prefixes the paths with
+        * \\?\ anyway so this is irrelevant... */
+}
+
+
 /* Given a path, which may not yet exist, get a set of flags that describe the
  * features of the volume the path is on. */
 int
@@ -337,20 +390,27 @@ win32_get_vol_flags(const wchar_t *path, unsigned *vol_flags_ret)
        wchar_t *volume;
        BOOL bret;
        DWORD vol_flags;
+       size_t drive_spec_len;
 
-       if (path[0] != L'\0' && path[0] != L'\\' &&
-           path[0] != L'/' && path[1] == L':')
-       {
-               /* Path starts with a drive letter; use it. */
-               volume = alloca(4 * sizeof(wchar_t));
-               volume[0] = path[0];
-               volume[1] = path[1];
-               volume[2] = L'\\';
-               volume[3] = L'\0';
-       } else {
+       drive_spec_len = win32_path_drive_spec_len(path);
+
+       if (drive_spec_len == 0)
+               if (path[0] != L'\0' && path[1] == L':') /* Drive-relative path? */
+                       drive_spec_len = 2;
+
+       if (drive_spec_len == 0) {
                /* Path does not start with a drive letter; use the volume of
                 * the current working directory. */
                volume = NULL;
+       } else {
+               /* Path starts with a drive letter (or \\?\ followed by a drive
+                * letter); use it. */
+               volume = alloca((drive_spec_len + 2) * sizeof(wchar_t));
+               wmemcpy(volume, path, drive_spec_len);
+               /* Add trailing backslash in case this was a drive-relative
+                * path. */
+               volume[drive_spec_len] = L'\\';
+               volume[drive_spec_len + 1] = L'\0';
        }
        bret = GetVolumeInformationW(volume, /* lpRootPathName */
                                     NULL,  /* lpVolumeNameBuffer */