win32: make stat(2) fetch additional metadata

Modify the WIN32 implementation of stat(2) to fetch inode number,
device id and number of hardlinks.  This requires opening a handle
to the target file so it will be slower.

A number of features can be enabled or start to work:

- tar can detect if an archive is being stored in itself;
- find can support the -inum and -links options;
- ls can display inode numbers;
- diff can detect attempts to compare a file with itself;
- du has better support for hardlinked files;
- cp can detect attempts to copy a file over itself.

1 files changed, 35 insertions, 4 deletions

diff --git a/win32/mingw.c b/win32/mingw.c
index 8217ec772..03636a04b 100644
--- a/win32/mingw.c
+++ b/win32/mingw.c
@@ -403,7 +403,7 @@ static int do_lstat(int follow, const char *file_name, struct mingw_stat *buf)
                 buf->st_ino = 0;
                 buf->st_uid = DEFAULT_UID;
                 buf->st_gid = DEFAULT_GID;
-                buf->st_nlink = 1;
+                buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 : 1;
                 buf->st_mode = file_attr_to_st_mode(fdata.dwFileAttributes);
                 if (S_ISREG(buf->st_mode) &&
                                 (has_exe_suffix(file_name) || has_exec_format(file_name)))
@@ -434,6 +434,30 @@ static int do_lstat(int follow, const char *file_name, struct mingw_stat *buf)
                         }
                 }
 
+#if ENABLE_FEATURE_EXTRA_FILE_DATA
+                {
+                        BY_HANDLE_FILE_INFORMATION hdata;
+                        HANDLE fh = CreateFile(file_name, 0,
+                                                        0, NULL, OPEN_EXISTING,
+                                                        FILE_ATTRIBUTE_NORMAL|FILE_FLAG_BACKUP_SEMANTICS,
+                                                        NULL);
+                        if (fh != INVALID_HANDLE_VALUE) {
+                                if (GetFileInformationByHandle(fh, &hdata)) {
+                                        buf->st_dev = hdata.dwVolumeSerialNumber;
+                                        buf->st_ino = hdata.nFileIndexLow |
+                                                (((uint64_t)hdata.nFileIndexHigh)<<32);
+                                        buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 :
+                                                                                hdata.nNumberOfLinks;
+                                }
+                                CloseHandle(fh);
+                        }
+                        else {
+                                errno = err_win_to_posix(GetLastError());
+                                return -1;
+                        }
+                }
+#endif
+
                 /*
                  * Assume a block is 4096 bytes and calculate number of 512 byte
                  * sectors.
@@ -522,12 +546,19 @@ int mingw_fstat(int fd, struct mingw_stat *buf)
                 buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
                 buf->st_blocks = ((buf->st_size+4095)>>12)<<3;
  success:
-                buf->st_dev = buf->st_rdev = 0;
+#if ENABLE_FEATURE_EXTRA_FILE_DATA
+                buf->st_dev = fdata.dwVolumeSerialNumber;
+                buf->st_ino = fdata.nFileIndexLow |
+                        (((uint64_t)fdata.nFileIndexHigh)<<32);
+                buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 : fdata.nNumberOfLinks;
+#else
+                buf->st_dev = 0;
                 buf->st_ino = 0;
+                buf->st_nlink = S_ISDIR(buf->st_mode) ? 2 : 1;
+#endif
+                buf->st_rdev = 0;
                 buf->st_uid = DEFAULT_UID;
                 buf->st_gid = DEFAULT_GID;
-                /* could use fdata.nNumberOfLinks but it's inconsistent with stat */
-                buf->st_nlink = 1;
                 buf->st_blksize = 4096;
                 return 0;
         }