MinGW readdir reimplementation to support d_type

The original readdir implementation was fast, but didn't
support the d_type. This means that git would do additional
lstats for each entry, to figure out if the entry was a
directory or not. This unneedingly slowed down many
operations, since Windows API provides this information
directly when walking the directories.

By running this implementation on Moe's repo structure:
  mkdir bummer && cd bummer; for ((i=0;i<100;i++)); do
    mkdir $i && pushd $i;
      for ((j=0;j<1000;j++)); do echo "$j" >$j; done;
    popd;
  done

We see the following speedups:
  git add .
  -------------------
  old: 00:00:23(.087)
  new: 00:00:21(.512) 1.07x

  git status
  -------------------
  old: 00:00:03(.306)
  new: 00:00:01(.684) 1.96x

  git clean -dxf
  -------------------
  old: 00:00:01(.918)
  new: 00:00:00(.295) 6.50x

Signed-off-by: Marius Storm-Olsen <marius@trolltech.com>
Signed-off-by: Steffen Prohaska <prohaska@zib.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/compat/mingw.h b/compat/mingw.h
index 4c50f5b1b..4f7ba4c13 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -235,3 +235,32 @@ int main(int argc, const char **argv) \
 	return mingw_main(argc, argv); \
 } \
 static int mingw_main(c,v)
+
+#ifndef NO_MINGW_REPLACE_READDIR
+/*
+ * A replacement of readdir, to ensure that it reads the file type at
+ * the same time. This avoid extra unneeded lstats in git on MinGW
+ */
+#undef DT_UNKNOWN
+#undef DT_DIR
+#undef DT_REG
+#undef DT_LNK
+#define DT_UNKNOWN	0
+#define DT_DIR		1
+#define DT_REG		2
+#define DT_LNK		3
+
+struct mingw_dirent
+{
+	long		d_ino;			/* Always zero. */
+	union {
+		unsigned short	d_reclen;	/* Always zero. */
+		unsigned char   d_type;		/* Reimplementation adds this */
+	};
+	unsigned short	d_namlen;		/* Length of name in d_name. */
+	char		d_name[FILENAME_MAX];	/* File name. */
+};
+#define dirent mingw_dirent
+#define readdir(x) mingw_readdir(x)
+struct dirent *mingw_readdir(DIR *dir);
+#endif // !NO_MINGW_REPLACE_READDIR