[PATCH 3/3] mingw: implement nanosecond-precision file times

["Karsten Blees via GitGitGadget" <gitgitgadget@gmail.com>]

From: Karsten Blees <blees@dcon.de>

We no longer use any of MSVCRT's stat-functions, so there's no need to
stick to a CRT-compatible 'struct stat' either.

Define and use our own POSIX-2013-compatible 'struct stat' with nanosecond-
precision file times.

Note: This can cause performance issues when using Git variants with
different file time resolutions, as the timestamps are stored in the Git
index: after updating the index with a Git variant that uses
second-precision file times, a nanosecond-aware Git will think that
pretty much every single file listed in the index is out of date.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
---
 compat/mingw.c   | 18 ++++++++++--------
 compat/mingw.h   | 36 ++++++++++++++++++++++++++----------
 config.mak.uname |  2 --
 3 files changed, 36 insertions(+), 20 deletions(-)

diff --git a/compat/mingw.c b/compat/mingw.c
index 07fc0b79a..26016d02e 100644
--- a/compat/mingw.c
+++ b/compat/mingw.c
@@ -592,9 +592,11 @@ static inline long long filetime_to_hnsec(const FILETIME *ft)
 	return winTime - 116444736000000000LL;
 }
 
-static inline time_t filetime_to_time_t(const FILETIME *ft)
+static inline void filetime_to_timespec(const FILETIME *ft, struct timespec *ts)
 {
-	return (time_t)(filetime_to_hnsec(ft) / 10000000);
+	long long hnsec = filetime_to_hnsec(ft);
+	ts->tv_sec = (time_t)(hnsec / 10000000);
+	ts->tv_nsec = (hnsec % 10000000) * 100;
 }
 
 /**
@@ -653,9 +655,9 @@ static int do_lstat(int follow, const char *file_name, struct stat *buf)
 		buf->st_size = fdata.nFileSizeLow |
 			(((off_t)fdata.nFileSizeHigh)<<32);
 		buf->st_dev = buf->st_rdev = 0; /* not used by Git */
-		buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
-		buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
-		buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
+		filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim));
+		filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim));
+		filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim));
 		if (fdata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) {
 			WIN32_FIND_DATAW findbuf;
 			HANDLE handle = FindFirstFileW(wfilename, &findbuf);
@@ -753,9 +755,9 @@ static int get_file_info_by_handle(HANDLE hnd, struct stat *buf)
 	buf->st_size = fdata.nFileSizeLow |
 		(((off_t)fdata.nFileSizeHigh)<<32);
 	buf->st_dev = buf->st_rdev = 0; /* not used by Git */
-	buf->st_atime = filetime_to_time_t(&(fdata.ftLastAccessTime));
-	buf->st_mtime = filetime_to_time_t(&(fdata.ftLastWriteTime));
-	buf->st_ctime = filetime_to_time_t(&(fdata.ftCreationTime));
+	filetime_to_timespec(&(fdata.ftLastAccessTime), &(buf->st_atim));
+	filetime_to_timespec(&(fdata.ftLastWriteTime), &(buf->st_mtim));
+	filetime_to_timespec(&(fdata.ftCreationTime), &(buf->st_ctim));
 	return 0;
 }
 
diff --git a/compat/mingw.h b/compat/mingw.h
index 571019d0b..9419b27e1 100644
--- a/compat/mingw.h
+++ b/compat/mingw.h
@@ -327,18 +327,41 @@ static inline int getrlimit(int resource, struct rlimit *rlp)
 }
 
 /*
- * Use mingw specific stat()/lstat()/fstat() implementations on Windows.
+ * Use mingw specific stat()/lstat()/fstat() implementations on Windows,
+ * including our own struct stat with 64 bit st_size and nanosecond-precision
+ * file times.
  */
 #ifndef __MINGW64_VERSION_MAJOR
 #define off_t off64_t
 #define lseek _lseeki64
+struct timespec {
+	time_t tv_sec;
+	long tv_nsec;
+};
 #endif
 
-/* use struct stat with 64 bit st_size */
+struct mingw_stat {
+    _dev_t st_dev;
+    _ino_t st_ino;
+    _mode_t st_mode;
+    short st_nlink;
+    short st_uid;
+    short st_gid;
+    _dev_t st_rdev;
+    off64_t st_size;
+    struct timespec st_atim;
+    struct timespec st_mtim;
+    struct timespec st_ctim;
+};
+
+#define st_atime st_atim.tv_sec
+#define st_mtime st_mtim.tv_sec
+#define st_ctime st_ctim.tv_sec
+
 #ifdef stat
 #undef stat
 #endif
-#define stat _stati64
+#define stat mingw_stat
 int mingw_lstat(const char *file_name, struct stat *buf);
 int mingw_stat(const char *file_name, struct stat *buf);
 int mingw_fstat(int fd, struct stat *buf);
@@ -351,13 +374,6 @@ int mingw_fstat(int fd, struct stat *buf);
 #endif
 #define lstat mingw_lstat
 
-#ifndef _stati64
-# define _stati64(x,y) mingw_stat(x,y)
-#elif defined (_USE_32BIT_TIME_T)
-# define _stat32i64(x,y) mingw_stat(x,y)
-#else
-# define _stat64(x,y) mingw_stat(x,y)
-#endif
 
 int mingw_utime(const char *file_name, const struct utimbuf *times);
 #define utime mingw_utime
diff --git a/config.mak.uname b/config.mak.uname
index 8acdeb71f..f179d7a1d 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -370,7 +370,6 @@ ifeq ($(uname_S),Windows)
 	RUNTIME_PREFIX = YesPlease
 	HAVE_WPGMPTR = YesWeDo
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease
-	NO_NSEC = YesPlease
 	USE_WIN32_MMAP = YesPlease
 	MMAP_PREVENTS_DELETE = UnfortunatelyYes
 	# USE_NED_ALLOCATOR = YesPlease
@@ -518,7 +517,6 @@ ifneq (,$(findstring MINGW,$(uname_S)))
 	RUNTIME_PREFIX = YesPlease
 	HAVE_WPGMPTR = YesWeDo
 	NO_ST_BLOCKS_IN_STRUCT_STAT = YesPlease
-	NO_NSEC = YesPlease
 	USE_WIN32_MMAP = YesPlease
 	MMAP_PREVENTS_DELETE = UnfortunatelyYes
 	USE_NED_ALLOCATOR = YesPlease
-- 
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