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Better mmap() emulation #486

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merged 3 commits into from Oct 13, 2015
Merged

Better mmap() emulation #486

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f21df00
win32mmap: set errno appropriately
dscho Oct 5, 2015
5cba588
mmap(win32): avoid copy-on-write when it is unnecessary
dscho Oct 13, 2015
100a1f1
mmap(win32): avoid expensive fstat() call
dscho Oct 13, 2015
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31 changes: 18 additions & 13 deletions compat/win32mmap.c
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Expand Up @@ -2,37 +2,42 @@

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,
PAGE_WRITECOPY, 0, 0, NULL);
hmap = CreateFileMapping(osfhandle, NULL,
prot == PROT_READ ? PAGE_READONLY : PAGE_WRITECOPY, 0, 0, NULL);

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if (!hmap)
if (!hmap) {
errno = EINVAL;
return MAP_FAILED;
}

temp = MapViewOfFileEx(hmap, FILE_MAP_COPY, h, l, length, start);
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");

return temp ? temp : MAP_FAILED;
if (temp)
return temp;

errno = GetLastError() == ERROR_COMMITMENT_LIMIT ? EFBIG : EINVAL;
return MAP_FAILED;
}

int git_munmap(void *start, size_t length)
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