From d5425d10ca68a297061f87f4460dd7e0b32b39a6 Mon Sep 17 00:00:00 2001
From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Fri, 22 Apr 2016 16:31:32 +0200
Subject: [PATCH] mmap(win32): avoid expensive fstat() call
On Windows, we have to emulate the fstat() call to fill out information
that takes extra effort to obtain, such as the file permissions/type.
If all we want is the file size, we can use the much cheaper
GetFileSizeEx() function (available since Windows XP).
Suggested by Philip Kelley.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
compat/win32mmap.c | 16 +++++++---------
1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/compat/win32mmap.c b/compat/win32mmap.c
index b836169b3ce..519d51f2b60 100644
--- a/compat/win32mmap.c
+++ b/compat/win32mmap.c
@@ -2,26 +2,24 @@
void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
{
- HANDLE hmap;
+ HANDLE osfhandle, hmap;
void *temp;
- off_t len;
- struct stat st;
+ LARGE_INTEGER len;
uint64_t o = offset;
uint32_t l = o & 0xFFFFFFFF;
uint32_t h = (o >> 32) & 0xFFFFFFFF;
- if (!fstat(fd, &st))
- len = st.st_size;
- else
+ osfhandle = (HANDLE)_get_osfhandle(fd);
+ if (!GetFileSizeEx(osfhandle, &len))
die("mmap: could not determine filesize");
- if ((length + offset) > len)
- length = xsize_t(len - offset);
+ if ((length + offset) > len.QuadPart)
+ length = xsize_t(len.QuadPart - offset);
if (!(flags & MAP_PRIVATE))
die("Invalid usage of mmap when built with USE_WIN32_MMAP");
- hmap = CreateFileMapping((HANDLE)_get_osfhandle(fd), NULL,
+ hmap = CreateFileMapping(osfhandle, NULL,
prot == PROT_READ ? PAGE_READONLY : PAGE_WRITECOPY, 0, 0, NULL);
if (!hmap) {