git/compat/win32mmap.c
Johannes Schindelin d5425d10ca 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>
2016-04-22 15:01:16 -07:00

47 lines
1.1 KiB
C

#include "../git-compat-util.h"
void *git_mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
{
HANDLE osfhandle, hmap;
void *temp;
LARGE_INTEGER len;
uint64_t o = offset;
uint32_t l = o & 0xFFFFFFFF;
uint32_t h = (o >> 32) & 0xFFFFFFFF;
osfhandle = (HANDLE)_get_osfhandle(fd);
if (!GetFileSizeEx(osfhandle, &len))
die("mmap: could not determine filesize");
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(osfhandle, NULL,
prot == PROT_READ ? PAGE_READONLY : PAGE_WRITECOPY, 0, 0, NULL);
if (!hmap) {
errno = EINVAL;
return MAP_FAILED;
}
temp = MapViewOfFileEx(hmap, prot == PROT_READ ?
FILE_MAP_READ : FILE_MAP_COPY, h, l, length, start);
if (!CloseHandle(hmap))
warning("unable to close file mapping handle");
if (temp)
return temp;
errno = GetLastError() == ERROR_COMMITMENT_LIMIT ? EFBIG : EINVAL;
return MAP_FAILED;
}
int git_munmap(void *start, size_t length)
{
return !UnmapViewOfFile(start);
}