win32: try to get link count for directories

On Unix the link count of a directory reflects the number of
subdirectories it contains.  Enhance readdir(3) to return file
types and use this to count subdirectories when stat(2) is called
for a directory.

As with other features that might slow down stat(2) this is
controlled by the build-time setting FEATURE_EXTRA_FILE_DATA.
(Commit d82db8e9a 'win32: make stat(2) fetch additional metadata').

(GitHub issue #254)

3 files changed, 36 insertions, 1 deletions

diff --git a/win32/dirent.c b/win32/dirent.c
index b7de19391..b5b379209 100644
--- a/win32/dirent.c
+++ b/win32/dirent.c
@@ -10,6 +10,17 @@ static inline void finddata2dirent(struct dirent *ent, WIN32_FIND_DATAA *fdata)
 {
         /* copy file name from WIN32_FIND_DATA to dirent */
         strcpy(ent->d_name, fdata->cFileName);
+
+#if ENABLE_FEATURE_EXTRA_FILE_DATA
+        if ((fdata->dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) &&
+                        (fdata->dwReserved0 == IO_REPARSE_TAG_SYMLINK ||
+                        fdata->dwReserved0 ==  IO_REPARSE_TAG_MOUNT_POINT))
+                ent->d_type = DT_LNK;
+        else if (fdata->dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY)
+                ent->d_type = DT_DIR;
+        else
+                ent->d_type = DT_REG;
+#endif
 }
 
 DIR *opendir(const char *name)
diff --git a/win32/dirent.h b/win32/dirent.h
index b38d0d133..214f80547 100644
--- a/win32/dirent.h
+++ b/win32/dirent.h
@@ -9,6 +9,9 @@ typedef struct DIR DIR;
 #define DT_LNK     3
 
 struct dirent {
+#if ENABLE_FEATURE_EXTRA_FILE_DATA
+        unsigned char d_type;
+#endif
         char d_name[PATH_MAX];  // file name
 };
 
diff --git a/win32/mingw.c b/win32/mingw.c
index 539aa48d2..c35b1d6af 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -588,6 +588,26 @@ static int is_symlink(const char *pathname)
         return 0;
 }
 
+#if ENABLE_FEATURE_EXTRA_FILE_DATA
+static int count_subdirs(const char *pathname)
+{
+        int count = 0;
+        DIR *dirp = opendir(pathname);
+        struct dirent *dp;
+
+        if (dirp) {
+                while ((dp = readdir(dirp)) != NULL) {
+                        if (dp->d_type == DT_DIR)
+                                count++;
+                }
+                closedir(dirp);
+        } else {
+                count = 2;
+        }
+        return count;
+}
+#endif
+
 /* If follow is true then act like stat() and report on the link
  * target. Otherwise report on the link itself.
  */
@@ -656,7 +676,8 @@ static int do_lstat(int follow, const char *file_name, struct mingw_stat *buf)
                                 buf->st_dev = hdata.dwVolumeSerialNumber;
                                 buf->st_ino = hdata.nFileIndexLow |
                                                 (((ino_t)hdata.nFileIndexHigh)<<32);
-                                buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 :
+                                buf->st_nlink = S_ISDIR(buf->st_mode) ?
+                                                        count_subdirs(file_name) :
                                                         hdata.nNumberOfLinks;
                         }
                         buf->st_uid = buf->st_gid = file_owner(fh);