1 files changed, 46 insertions, 0 deletions
diff --git a/compat/win32mmap.c b/compat/win32mmap.c
new file mode 100644
index 000000000000..519d51f2b60a
--- /dev/null
+++ b/compat/win32mmap.c
@@ -0,0 +1,46 @@
+#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);
+}