[PATCH 3/3] mmap(win32): avoid expensive fstat() call
- From
Johannes Schindelin <johannes.schindelin@gmx.de>
- Date
- Apr 22, 2016, 14:31 UTC
- Message-ID
- <54698524fa95e2f83167ca78205749f855bfaee6.1461335463.git.johannes.schindelin@gmx.de>
- In-Reply-To
- <cover.1461335463.git.johannes.schindelin@gmx.de>
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> --- compat/win32mmap.c | 16 +++++++--------- 1 file changed, 7 insertions(+), 9 deletions(-)
diff --git a/compat/win32mmap.c b/compat/win32mmap.c index b836169..519d51f 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) {
-- 2.8.1.306.gff998f2